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Conservat ion o f Wal l Paint ing Department
COURTAULD I N STITUTE OF ART
Somerset House, Strand, London WC2R 0RN Telephone +44 (0)20 7848-2848 [email protected]
This is a dissertation accepted for a Postgraduate Diploma in the
Conservation of Wall Painting in the Conservation of Wall Painting Department, Courtauld Institute of Art, University of London.
It is unpublished and
copyright is held by the author. No quotations or information derived from it
may be published without the prior written consent of the author,
who may be contacted through the address above.
AN INVESTIGATION OF THE USE OF SOLVENT GELS FOR
THE REMOVAL OF WAX-RASED COATINGS FROM WALL PAINTINGS
TOBIT CURTEIS
Courtauld Institute ofArt/Getty Conservation Institute,
Conservation of Wall Paintings Department.
July 1991
CONTENTS
Acknowledgements.
1. Summary.
2. Introduction.
3. Solvent Gel Principles.
4. Gel Components.
4.1 Carbopol
4.1.1 Thickening mechanisms of Carbopol.
4.1.2 Amines for Neutralisation.
4.1.3 Surfactants.
4.1.4 Clearance.
4.1.5 Possible drawbacks with Carbopol.
4.2 Pemulen.
4.2.1 Thickening mechanisms of Pemulen.
4.2.2 Drawbacks of Pemulen.
4.3 Cellulose materials
5. Desiderata for Test Sites.
6. Test Methodology and Procedure.
6.1 Examination and Analysis.
6.2 Preparation of Carbopol gels.
6.3 Test Procedure.
6.4 Clearance Tests.
7. Holcot Church.
7.1 Introduction.
7.2 Painting Condition.
7.3 Cross-section analysis and SEM.
7.4 FTIR and Thermomicroscopy.
7.5 Solvency parameter tests.
7.6 Solvent gel tests.
8. The Holy Sepulchre Chapel,
Winchester Cathedral.
8.1 Introduction.
8.2 Technique.
8.3 Conservation History.
8.4 Painting Condition.
8.5 Cross-section analysis and SEM.
8.6 FITR and Thermomicroscopy.
8.7 Solvency parameter tests.
8.8 Solvent gel tests.
9. Westminster Abbey Chapter House.
9.1 Introduction.
9.2 Technique.
9.3 Conservation History.
9.3.1 G. G. Scott.
9.3.2 Prof A. H. Church
9.3.3 H. M. Office of Works.
9.3.4 English Heritage.
9.4 Painting Condition.
9.5 Cross-section analysis and SEM.
9.5.1 Binding Media.
9.6 FTIR and Thermomicroscopy.
9.7 Solvency parameter tests.
9.8 Solvent gel tests.
10. Analysis for Residual Materials.
11. Conclusion and Further Research.
12. Bibliography.
13. Appendices.
1. Recipes for wax and wax resin
preservatives advocated byProfessors Church and Tristram.
2. Solvent Gel formulas.
3. Teas Chart showing the solvency
parameters of the most effective
solvent gels in relation to the
solubility region of beeswax.
4. Solvent Gel Tests,Summary of
results reported in the proformas.
5. Fourier Transform Infrared Spectra.
6. Nitromors paint stripper.
7. Solvent Gel Tests Carried out in the
Chapel Of Our lady Undercroft,
Canterbury Cathedral.
8. Site proformas.
14. Plates.
Acknowledgements
For permission to examine and sample the paintings at the four sites studied I am
grateful to the Dean and Chapter of Canterbury Cathedral and to Mr. Wolfgang
Gartner of the Wallpaintings Workshop; the Dean and Chapter of Winchester
Cathedral and especially to Mr. John Hardacre for his help and advice, the Parish
Council of Holcot Church and the Rev. Anthony Watkins; and to Mr. Jan Keevil,
Head of the English Heritage Conservation Studio, for Westminster Abbey Chapter
House.
For technical information on materials and for product samples I would like to
thank Mr. G. Stead and Mr. John Gallagher of B. F. Goodrich and Mr. C. Drake of
AKZO Chemicals. Ms. Zahira Veliz, Mr. Alan Phenix (Courtauld Institute) and Ms.
Lucia Scalisi (Victoria and Albert Museum) gave much helpful advice on
formulation of the gels.
I am particularly grateful to Ms. Marianne Odlyha of Birkbeck College for her
constant help and valuable advice especially in regard to the analysis including
Fl'lK, DSC and Thermomicroscopy. I am also very grateful for the help of Mr.
Raymond White, Scientific Department, National Gallery, particularly in the area of
interpretation of IR spectra.
For their advice and support throughout and in all areas of this research I would
especially like to thank my two supervisors Ms. Aviva Burnstock, Scientific
Department, National Gallery, who also carried out the SEM and EDX analysis,
and Ms. Katherine Powell of the Courtauld Institute.
Finally I would like to thank Mr David Park and Ms. Sharon Cather of the
Courtauld Institute for their continual help during the course of this work.
-5-
Summarv
The effects of the preservative' coatings commonly applied to wall paintings in the19th and first half of the 20th centuries, have been both damaging and disfiguring in
the longer term. Typically these coatings consist of either pure beeswax or a mixture
of beeswax and a natural resin applied to the painting surface. The penetration of
the coatings due to the porosity of wall paintings and the fragile nature of many ofthe paint surfaces, when treated, has made the removal of such materials extremely
difficult.
The solvent gels formulated for this study were intended to have very specific
solvency parameters allowing them to dissolve a particular material, without
endangering the other vulnerable components of the paint surface. The system was
not be intended as an all-encompassing solvent mixture for the removal of all
coatings on the paint surface. If there were more than one coating of a different
nature, for instance a varnish layer covered by a wax resin coating, it would be
necessary to use two different gels, each tailored by their solvent mixtures to the
specific problem of each layer.
The complete removal from the painting of all components of the gel system, forms
an integral part of gel cleaning process. The long-term effects of the non-volatile
components and their interaction with the materials of wall paintings are not fully
understood and to ensure that no damage is caused by these materials the
implementation of an adequate system of clearance must be undertaken.
The investigations into the feasibility of such a cleaning system drew heavily on the
work of Richard Wolbers who was responsible for developing the theory andformulating a range of organic solvent gel systems for particular cleaning problems
in the field of easel painting conservation. The formulas developed by him providedthe starting point for the development of a series of solvent gels that were applicableto the problems faced in wall paintings.
Materials were chosen that had a known history of usage in general conservation,
although some of these had not been applied to wall painting conservation. Much ofthe initial work was theoretical, involved with the chemistry of producing a gelsystem with the necessary attributes. The main gelling agent, a high molecular
weight polyacrylic acid, Carbopol, was chosen due to its ability to effect very viscousgels at relatively low percentages. Due to the high wax component of the coatings itwas necessary to produce a series of highly aromatic solvent gels. A program of tests
was undertaken on a number of wall paintings that had been treated with a wax or
wax/resin coating in order to evaluate both the cleaning effect of the gels and theirsubsequent clearance. The possibility of conducting the tests on laboratory modelswas evaluated, but despite the complications caused by the lack of chemical controlon actual paintings, it was felt that due to the problems of reproducing the necessaryconditions on a model, the results obtained from actual paintings would of be morevalue in examining the effects of the gels.
Cross-sections were taken to establish the stratigraphy of both the coatings and thepainting. This enabled the characterisation of differing surface coatings and thetheir relative thickness to be established in order to make a comparison with the
situation after cleaning. These samples were examined both on the surface and incross-section using visible and ultra-violet microscopy and scanning electronmicroscopy. Samples of the surface coating were analysed using FTIR in order toestablish the exact nature of the material. This was necessary so that the solvent
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component of the gel could be prepared to dissolve that particular material.
After the cleaning and clearance tests had been carried out, further samples weretaken in order to evaluate the effects of the gels as well as to check for possible
residues. Examination was carried out using visible, ultra violet and scanningelectron microscopy. In order to examine the problem of clearance more fully,controlled tests were carried out on a laboratory model, allowing a more detailed
series of experiments to take place.
The results of the project were extremely encouraging indicating that it is possible to
produce a solvent gel system with the necessary solvency parameters to remove thecommonly encountered wax coatings. No residues of the material from the cleaningsystem were detected with FTIR or SEM after clearence had taken place. This latterresult must however be qualified. A negative result such as this means simply thatno residue has so far been found, it is not a guarantee that no trace of the material ispresent and further more sensitive analysis should be carried out to ensure this.
-7-
2. Introduction
During the nineteenth and the first half of this century, wax and resin based
treatments were commonly believed to be the most effective method for the
'preservation' of wall paintings. The original premise behind the application of such
coatings lay in the mistaken belief that classical Roman paintings were executed in
encaustic technique, thus leading to the conclusion that wax was responsible for
their longevity and survival. The writings of both Pliny and Vitruvius appeared to
confirm that the use of wax was advantageous in protecting fresco paintings.1
The saturation of the painting with such coatings was seen as a general cure for the
various types of damage encountered and with the active involvement of respected
men such as Professors E. W. Tristram and A. H. Church, who were regarded as
authorities on such matters, became the accepted treatment for almost all wall
paintings. An application of such a coating effectively restored cohesion to
powdering surfaces, and was equally effective at readhesion of flaking layers.
Perhaps the effect which was initially most apparent was the immediate visual
change caused by the saturation of the paint layer. The result was to change wall
paintings from damaged'and apparently faded objects into bright, sound decorative
elements more in keeping with the contemporary aesthetic.
Such effects were relatively short term, and it soon became apparent that the use of
wax and resin coatings was the major cause of the damage that began to appear on
paintings. Serious discoloration and flaking were seen to occur. This damage fell
broadly into two categories, aesthetic and structural. The aesthetic alteration
brought about by such coatings are often the most noticeable forms of damage. Pure
beeswax is a very stable polymer, that does not discolor or break down with age. The
main reason beeswax coatings appear to darken is that at room temperatures the
1 Cather & Howard 1986
-8-
wax is relatively soft,2 and will absorb atmospheric dirt that settles on it, including
the byproducts of the burning of fuels such as oil and coal (commonly used in the
past to fuel heating systems in parish churches), which will remain fixed to the
surface of the wax, thereby obscuring the painting. A further reason for the
discoloration is that some of the preservative coatings consisted of a mixture of wax
and a natural resin such as copal.3 During the oxidization and aging process of
natural resins darkening occurs, thus further obscuring the paint surface.
The main reason for the physical damage caused by these coatings relates to the
porous nature of lime-based wall paintings. This porosity allows moisture and water-
soluble materials such as salts to move freely through the structure of the painting.
If this porosity is significantly reduced by the application of an impermeable coating
over the surface of the painting the effect will be to set up internal stresses within
and below the paint layer. Soluble salts that would have crystallised on the surface
of the painting causing little or no physical damage will now crystallise in the
restricted space of the pores below the surface. The expansion of volume that occurs
in the process of crystallisation will cause the pores to break and thus disrupt the
paint surface causing both decohesion and delamination. The application of wax
based coatings to oil or secco paintings was in some ways potentially less damaging.
Due to the nature of the medium, such paintings were far less porous than lime-
based wall paintings, and therefore a coating of wax would not considerably alter the
rate of penetration of moisture. The damage caused in these cases is aesthetic with
the darkening of the coating, described above, obscuring the paint surface.
It was not until 1953 when the committee set up by the Council for the Care of
Churches (CCC) to examine the practices employed in the conservation of wall
2 The glass transition temperature of beeswax is
3 Appendix 8.
-9-
paintings, published a letter in the Times denouncing the use of '....Wax or any other
surface coating which may impeded the free evaporation of any moisture...' that the
damage caused by the practice was generally acknowledged.4 In 1959 the CCC
published a full report on the subject setting out the damaging effects caused by
such 'preservative' treatments and advising against their use.5
Traditional methods for the removal of these coating have relied on the use of
strongly acting organic solvents which aim to remove all components of the surface
coatings through the application of a single type of cleaning agent. The advantages
of organic solvents supported in a gel system rather than as free and highly volatile
agents have long been apparent to conservators.6 The most commonly used cleaning
system in recent years has been Nitromors, a commercially available paint stripper.
The formula for this product has changed a number of times since it was first
introduced in the early 1940s, but its main components have altered little and have
always been based on a mixture of methanol and dichloromethane supported in a
gelling medium containing both paraffin wax and a small component of cellulose.7
The disadvantages of such a material are twofold. The first is that a commercial
paint stripper such as this is intended to encompass the removal of as wide a range
of organic material possible. The structures of wall paintings can be very complex
with a number of delicate and soluble layers. Such a material will not only dissolve
the wax and resin coatings, but also any other vulnerable organic components such
as surface glazes and medium found in secco wall paintings. The second
disadvantage lies with the components of the material themselves. For a long period
of time, Nitromors has been used without a full knowledge of its chemical
4 The Times, 21st February 1953.5 Central Council for the Care of Churches, 1959.6 The use of gels in wall painting conservation is not limited to organic solvents. The use of AB 57, acombination of sodium and ammonium bicarbonates in a cellulose gelling medium, is a well
established treatment for the removal of insoluble salts. Mora, Mora and Philippot 1984. pp.342.
7 Appendix 6.
-10-
components or the possible effects of chemical decomposition that may occur in the
longer term if any of the material is left on the painting. A commercially available
paint stripper would tend to be concerned with the short-term effects of the material
and not the longer term that would be of concern to the conservator.
3. Solvent Gel Principles
The principles behind the use of a gel system to alter the working properties of
organic solvents has clear advantages in areas of conservation. The gel support
reduces the rate of evaporation and diffusion of the solvent mixture in which it is
dissolved by increasing the viscosity of the system thus enabling an increased contact
period in a discrete localised area of the surface of the object. The result of this
reduction in solvent volatility is to 'concentrate' the effect of the solvent, increasing
the ability to more effectively dissolve the material on which it is working. There is
no evidence that the use of a gel support alters the solubility parameters of the
solvent, simply that within those parameters the action of the solvent appears to be
enhanced. The direct application of this phenomenon is that where a 'strong' free
solvent (a solvent with a solubility parameter in the center of the region of the
solute), would be required the same effect could be achieved using a ^weaker'
solvent (one with a solubility parameter towards the edge of the of the region of the
solute) supported in a gel system. Containing the solvent in such a way might also
reduce the amount of undercutting, as discussed by Burnstock and White,8 that can
occur when there is no control over the penetration of a free solvent. This is of
course an advantage when dealing with complex layer structures of soluble organic
materials as it allows far more specific solubility to be achieved, more readily
allowing the removal of individual layers with potentially less 'strong' and hazardous
solvents.
8 Burnstock and White 1990.
-11-
Recently significant advances have been made with the application of such gels to
cleaning problems encountered on easel paintings through the work of Richard
Wolbers. His use of an acrylic acid polymer, Carbopol, as a gelling agent for organic
solvents marked a significant advance on the use of the cellulose materials more
commonly used.9 Carbopol had the advantage of producing a thixotropic viscous gel
at a very low percentage due to its high swelling ability and could more easily be
used in conjunction with a wide range of solvents. Wolbers developed the rationale
for the use of such gel systems with very specific parameters to work on individual
parts of a particular cleaning case, rather than on the case as a whole.
The application of these principles to the removal of wax and wax/resin coatings
from wall paintings was clearly desirable as the problems associated with the
removal of soluble materials encountered in this field of conservation are complex.
The most important difference between easel paintings and wall paintings in terms
of surface is the high level of porosity and topography of many wall paintings. The
effect of this is that at the interface with the paint surface, there is no longer the
relatively discrete separation between coating and pigment layer encountered on
easel paintings, but with a coating that penetrates the surface to various depths,
becoming an almost integral part or the matrix of pigment and binder. The degree
to which this occurs depends on the nature of the painting technique and its
condition. In cases where there is decohesion occurring within the paint layers this
situation is further complicated. The problem is further complicated by the method
in which the coating was applied. In many cases this was carried out using heat
treatments in order to drive the material deep into the painting in the belief that the
greater the penetration, the more stable the treatment.10
9 HPMC is used by Wolbers as a support for resin soaps and enzyme cleaning systems.10 Appendix 1.
-12-
The ability to finely control solvency parameters offered by gels has a number of
further advantages which apply in all fields of painting conservation, but are
particularly important in the field of wall paintings. First among these is the scope
for a reduction in toxicity of the solvents used. In many cases when free solvents are
used it has been necessary to use those with relatively high levels of toxicity to gain
the solvency parameters required. The use of large quantities of dichloromethane
with a MEL of 350 mg/m3 and LD 50 of 2136 mg/kg oral, ratn both free and in
Nitromors paint stripper, is the standard method for the removal of wax coatings
from English wall paintings.12 Using solvents in a gel system a similar area of
solvency can often be achieved with a less toxic solvent. The toxic effect on the
conservator would also be limited due to the reduction in evaporation rate of the
solvent caused by the gel.
A further advantage in the use of solvent gels is the reduction in mechanical action
on the paint layer from that caused by continual swab rolling with free solvents.
Solvent gels are applied to the wall with a swab and then gently moved, until they
area removed with a second swab. Contact between the surface of the painting and
the swab is minimal. Such mechanical action as there is can be further reduced by
the use of an intervention layer of a permeable material such as Japanese tissue
between the gel and the paint layer, thus reducing the risk of damage when working
on a damaged or delicate surface. The use of an intervention layer also acts as a
considerable aid in the removal of the majority of the gel from the surface of the
painting.
An essential part of the cleaning process using solvent gels is the clearance
11BDH Hazard Data Sheets. MEL or Maximum Exposure Limit is taken from the HSE guidance
note EH40, 'Occupational Exposure Limits', and is an indication of the maximum amount of thematerial that it is considered acceptable to be exposed to. LD or Lethal Dose indicates the toxicityof a material on a rat or mouse (as stated) as a guide to its toxic effect on humans.
12Ballantyneetal. 1988
-13-
procedure that must be undertaken in order to remove all residues of the gel from
the painting. Although a number of recent studies have examined the possible
effects of some residual materials,13 the long-term effects of many of the gel
components and any interaction with the materials of the painting have not been
fully examined. The complete removal of residual material must therefore form an
integral part of the overall cleaning method.
4. Gel Components
The two basic components necessary for a solvent gel are the gelling agent and the
solvents themselves. Further components are subsidiary to these in that they are
specific to a particular gelling agent (or solvent) and are intended either to make
the solvent and the gelling agent compatible, or to alter the effect of the gel on the
solute. Into this secondary category can be placed surfactants, pH buffers and
neutralising mechanisms. It is principally, therefore, the choice of gelling agent
which dictates the nature of other components in the solvent gel.
4.1 Carbopol™
Carbopol resins are long-chain acrylic acid polymers cross-linked with a polyalkenyl
polyether (carboxy polymethylene), with pH of 2.5-3.0 in a 1% water dispersion.14
Carbopol in its undissolved state is a white powder consisting of tightly coiled long-
chain molecule. When it undergoes certain reactions, the molecule uncoils, thus
causing the viscosity of the solution to rise. It is available in a wide range of
molecular weights ranging from approximately 450,000 (Carbopol 907) to 4,000,000
(Carbopol 940).15 The molecular weight affects the surface tension and viscosity of
the final product therefore it is important that the most suitable one is chosen to
13 Wolbers 1990A, Burnstock and White 1990.14 Goodrich B.F. CARBOPOL Water Soluble Resins. Technical data. Ohio.15 Molecular weights given by the manufacturers are approximate. Carbopol 907 = 450,000,Carbopol 910 = 750,000, Carbopol 941 = 1,250,000, Carbopol 934 = 3,000,000, Carbopol 940 =4,000,000. (Carbopol 954 mw 3,000,000 is no longer widely available.)
-14-
achieve optimum performance for the solvent gels.16
Carbopol 934 or 940 were chosen as the most suitable gelling agents for the gels
tested in this project due particularly to their ability to produce the necessary high
levels of viscosity at very low percentages. They were also adaptable to all the
solvent mixtures required, both polar and non-polar, for the cleaning of wall
paintings.
Fig.l. Structural Formula of Carbopol
4.1.1 Thickening Mechanisms of Carbopol.
Although Carbopol resins are predominantly hydrophilic they can also be used in
non-aqueous solvent systems. There are two basic methods for using Carbopol as a
thickening agent. The first, the hydrogen bonding method, can only be employed in
polar systems, while the second, the neutralisation method, is suitable for both polar
and non-polar systems.
Hydrogen Bonding.
This system requires the use of a solvent capable of donating an hydroxyl group. The
resulting hydrogen bonds between the carboxyl groups of the Carbopol and the
hydroxyl groups of the solvent donor will cause the molecule to uncoil and
thickening to occur. The solvents capable of this are limited to polyhydroxy, and
polyethoxy solvents such as diols, triols and polyols. This process is far slower than
16 Carbopol 934 and 940 were found to be the most efficient in terms of the low percentage
required to produce the desired viscosity for the solvent gels.
-15-
the neutralisation method and it may take a number of hours for full thickening to
occur. Empirical observation through experimentation undertaken in the course of
this work has shown that this process does not achieve the viscosity of neutralised
systems using the same percentage volume of Carbopol. A further problem for this
study is that the use of the necessary hydroxyl donor solvents may adversely effect
the solubility parameters required for the particular gel.
Fig.2. Schematic Depiction of a Molecule of Carbopol in its
uncoiled state with hydrogen bonding.
V
Neutralisation.
For this method the resin is neutralised by the use of a base to produce a salt
soluble in the required solvents. In an aqueous or polar solution this can be
achieved using a base such as ammonium or sodium hydroxide. A 3% aqueous
solution of Carbopol can produce a viscosity of 30,000 to 40,000 cP without
neutralisation. A level of viscosity from 40,000 to 60,000 can be produced by a 0.5%
solution of Carbopol in water after neutralisation to pH 7 - 7.8 with sodium
hydroxide.17 In a non-polar solvent system (such as those considered in these tests)
or in one where the use of these bases is undesirable the resin can be neutralised in
the same way with an amine.18
17 Goodrich B.F. CARBOPOL Water Soluble Resins. Technical data. Ohio, pp 13-1418 The use of sodium hydroxide as part of a cleaning system for wall paintings is consideredundesirable as the free sodium ions introduced into the wall will readily react with other free ions
producing highly soluble salts which are inherently dangerous to wall paintings. Ammonium
hydroxide is sometimes used for cleaning wall paintings, and it is possible that it could also be use
-16-
The pH of the overall gel is not only important for the effect it may have on the
paint surface, but also for the stability of the gel.19 It was possible that during the
cleaning process the dissolved material from the surface of the painting may cause
the pH of the gel to alter to an extent that it would break down. The use of a pH
buffer was considered to counter this effect. Buffers are solutions that will enable
the main solution to retain a constant pH when small quantities of acids or bases are
added. Empirical experiments were carried out to establish whether the pH of the
gel was altered, during its application, to an extent where the use of a buffer solution
would become necessary.20 The results showed that the alteration in the pH of the
gel was negligible. It remained physically stable throughout the test, even when
applied to a volume of wax far greater than that which would be encountered in the
field.
Fig.3. Schematic Depiction of a Molecule of Carbopol in its
uncoiled state after neutralisation with ammonium hydroxide.
4.1.2 Amines for Neutralisation.
For the purposes of this study it was necessary to work with aromatic and aliphatic
as the neutralising agent in a polar solvent gel, without risk to the paintings.19 The pH of the gels formulated for this work was approximately 7.5.20 The pH of the solvent gel was tested in its fresh state. A given quantity of beeswax was thendissolved in the gel and a second test for pH was made. These were found to be the same.
-17-
hydrocarbon solvents in order to obtain the required solvency parameters to remove
wax-based materials. The use of a neutralising mechanism offered the most
adaptable and viscous gel, and the non-polar solvents were not suitable for
hydrogen bonding. It was therefore necessary to use an amine that would produce a
Carbopol salt soluble in aromatic and aliphatic hydrocarbon solvents.
A wide range of amines were examined and/or tested as possible neutralising agents
for the gels.21 Ethomeen C-25, (polyoxyethylene(15)cocoamine) and Ethomeen C-
12, (Cocobis(2-hydroxethyl)amine) appeared to offer the most efficient
neutralisation enabling the Carbopol to be dissolved in the required aromatic
solvents22. However after extensive testing Ethomeen C-12 proved to be the most
effective of the two at the lowest percentages.23 Virtually insoluble in water, it is
readily dissolved in aromatic solvents, and has a relatively low cationic surfactant
HLB value of 10 compared to that of 19 for Ethomeen C-25.24 It also has the added
advantage of relatively low toxicity with an LD 50 of 1500 mg/kg.25
Fig.4. Structural Formula of Ethomeen C-12
CH2.CH2.OH
R-N (R = Coco alkyl)
CH2.CH2.OH
The fact that Ethomeen C-12 is not only an amine but also a surfactant, albeit a
21 Those considered included Ethomeen C-12, Ethomeen C-25, Armeen-OD (products ofAKZOChemicals), Dodecylamine & Triethanolamine.
22 xylene and White Spirit.23 Tests using Ethomeen C-12 to gel Carbopol with aromatic systems have already been carried outby a several easel painting conservators, showing successful results had depended on the use of very
exact amounts. (Pers. comm. Lucia Scalisi and Alan Phenix)
24 Hydrophile/Lipophile Balance value. The HLB value is a scale used to compare the relativeemulsifying properties of surfactants. It runs from 0 to 40 (0 is the weakest) and is established by
either experimental or mathematical methods.
25 AKZO Chemicals.
-18-
mild one, is of concern due to the possible problems of clearance that might be
presented.
4.1.3 Surfactants.
By forming bonds between polar and non-polar materials surfactants reduce the
surface tension between the gel and the solute increasing the intimate surface
contact (Vetting') and thereby increasing both the homogeneity and the potency of
the cleaning action.26 This same action could also cause greater penetration of the
substrate resulting in problems of clearance. The inclusion of a suitable surfactant in
a gel can also allow the addition of a solvent that is not miscible with the main
solvent, thus permitting a fine manipulation of the solubility parameters of the
overall system, however the surfactant may itself alter the solubility parameters of
the gel.
The possible problems involved with the use of surfactants in painting conservation
have been the subject of a number of recent discussions.27 All of these have
concentrated on the effect of surfactants on easel paintings, and while many of these
also occur on wall paintings, there are further complications associated with wall
paintings. Most important of these are the effects of the surfactant on the irregular
topography and porous substrate typical of wall paintings. Due to the ability of
surfactants to reduce surface tension there is a greatly increased tendency to
penetrate the painting to some depth. The danger that this could result in the
surfactant remaining within the substrate, avoiding the clearance procedure, is
present in all paintings, however the open structure of wall paintings makes it all the
more acute. The long-term results of this are unclear and it appears probable that
the presence of a residual surfactant could increase the hydrophilic tendency of the
26 This effect will vary in relation to the polar/non-polar nature of both the gel and the solute.
27 Southall 1990, Wolbers 1990A, Burnstock and White 1990.
-19-
painting. This would encourage increased penetration of moisture commonly
present in an uncontrolled atmosphere, which in turn could effect the movement of
soluble salts and other water-related damage mechanisms in a way that would
clearly be detrimental to the painting as a whole. The possibility in the long term of
damaging interaction between any residual surfactant and the materials of the wall
painting is an area that is as yet unclear and requires further investigation. It is
therefore of the utmost importance that if surfactants are used as part of a cleaning
system, they are completely removed afterwards.
4.1.4 Clearance.
As the solvents are volatile they do not present a direct clearance problem, however
the two non-volatile components, the Carbopol and the Ethomeen C-12, are the
materials that must be considered. Ethomeen C-12 is virtually insoluble in water,
however it can be dissolved in aromatic solvents. This is also true of most of the
Carbopol which will have been converted by the amine to a salt. There is a
possibility that some of the Carbopol may not have reacted to form a salt and in this
form will be insoluble in aromatics but readily water-soluble. Although this would
represent only a tiny proportion of the overall volume of the Carbopol, it is
necessary to deal with it at this stage, because once it has been allowed to dry, it
becomes far more difficult to redissolve.28
Clearance is further complicated be the physical nature of the surface of many wall
paintings. As well as the porosity associated with medium-thin secco or buon fresco
technique there are the complications caused by the very uneven surfaces commonly
encountered on wall paintings. The particular hazard associated with the clearance
of solvent gels is the tendency of the deep interstices to retain relatively large
28 Pers.comm. G.Stead. The reason for this is not a change in the chemical structure of theCarbopol, but rather the physical structure that occurs when it dries and reforms into larger lumps.
This reduces the ability of the water to gain the surface contact with the individual grains required
for the quick dissolution.
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amounts of the gel.
The clearance procedure must therefore involve both aqueous and aromatic
solvents. In order to avoid increasing the risk to soluble components of the painting,
the aromatic solvent used should the same that contained in the gel. The same
caution exercised when applying the gels should be continued here as the solvency
parameters of other soluble materials of the painting may coincide with those of the
material removed by the gel. This should be followed by aqueous clearance which
requires further caution. The gel itself contains very low concentrations of water, so
it is possible to use it with minimal risk over a water-sensitive surface that may be
put at risk by this stage of the clearing. Both clearance solvents are applied using
cotton wool swabs, in order to absorb the dissolved residues.
4.1.5 Possible drawbacks with Carbopol
A possible disadvantage with the use of Carbopol as the gelling medium is its
tendency to react with certain of the materials commonly found in wall paintings.
The polyacrylic acid produces COO" ions which can complex certain bivalent and
trivalent ions such as calcium and magnesium. Such a reaction would be of serious
concern in the field of wall painting conservation due to the presence of large
amounts of both these ions either as part of the original material or in the form of
soluble salts. Once this reaction has taken place the Carbopol becomes insoluble in
water and could present a serious clearance problem. It is possible that once the
Carbopol is formed into an amine salt during gelling, less reactive sites will be
available for the complexing to occur, thus reducing the possibility of a reaction. No
hard data is available on the exact nature of these reactions, however certain
empirical tests have been carried out which indicate that in its unneutralised state
the Carbopol reacts swiftly with the metal ions to become insoluble.29
29 Pers. comm. G.Stead. 14.3.91. Empirical tests were carried out with Carbopol and cement in
order to test the complexing of ions present in the mixture. Dry Carbopol was added to dry cement
which was then mixed with water. At first the result was viscous, but in a matter of minutes it
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42 Pemulen™
Pemulen, a product of B.F.Goodrich, is described by the manufacturers as a
^polymeric emulsifier'. It consists of a polyacrylic acid backbone similar to Carbopol,
copolymerised with fatty comonomers (the nature of which is proprietary
information). The polyacrylic acid part of the molecule is hydrophilic while the
comonomer is lipophilic resulting in a molecule with amphipathic or surfactant
properties. The effect of this is that the molecule is soluble in both polar and non-
polar solvents and is able to act both as a thickening and emulsifying agent.
4.2.1 Thickening mechanism of Pemulen.
The method recommended by the manufacturers of thickening a solution with
Pemulen (pH 2.5-3.0 at 1% in H2O) is by neutralisation using a base such as sodium
hydroxide. It would also be possible to thicken an aqueous solution by adding
Pemulen directly to it, however without neutralisation, the solution would remain
strongly acidic.
4.2.2 Drawbacks of Pemulen.
As with Carbopol, the polyacrylic acid will produce COO- ions able to complex
bivalent and trivalent ions such as calcium or magnesium.30 The copolymer is
considered to be very stable and this reaction would not cause it to break up,
however the reaction does cause the molecule, like Carbopol, to become
thinned to a liquid. This was thought to be due to the Carbopol chelating the calcium ions of the
lime in the cement and thus becoming insoluble in the water and thus inactive. A second
experiment was carried out neutralising Carbopol with sodium hydroxide in order to fill all the
reaction sites and inhibit the reaction with the calcium ions. This was then mixed with the cement
that had already been mixed with water. The result was a stable viscous mixture which did not break
down, suggesting that in its salt form the sites on the Carbopol were not free to complex other ions.
30 It is possible that the occurrence of complexing would be reduced by the process of neutralisationin much the same way as was proposed for Carbopol.
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insoluble.31 Apart from the obvious undesirability of leaving foreign materials on
the wall painting there is the possibility of further complications caused by the
amphipathic properties of the molecule, (discussed in section 4.1.4 on clearance),
resulting in ionic bonding of the surfactant molecule to the painting.
4.3 Cellulose Materials
Cellulose gelling agents such as carboxymethyl cellulose or hydroxypropylmethyl
cellulose have commonly been used as thickening agents in certain areas of
conservation.32 The principle by which they work is one of bulking out the system
into which they are introduced. When in aqueous solution the tightly packed long
cellulose chains are swollen by hydrogen bonding of the water. The gelling efficiency
is relatively low in terms of percentage weight to viscosity, and the amount needed
to achieve the degree of gelling required for this work would be extremely high
compared to a system based on a swelling material such as a polyacrylic acid
polymer. A further problem with the use of cellulose gelling agents on wall paintings
is one of clearance. Carboxymethyl cellulose is hygroscopic with an equilibrium
moisture content of approximately 18% at 60% R.H.33 Were some of the material
to become trapped in the porous substrate, it would provide nutrition for the
microbiological growth common in an uncontrolled environment. It is also known to
contract on drying which could present the danger of flaking of the paint layer.
5. Desiderata for Test Sites.
It was decided that the majority of the tests would be carried out on actual paintings
as opposed to specially prepared models. The main problem with such models is
that of aging and reproduction of the widely ranging contaminants. The alteration of
31 pers.comm., Mr C.Drake 21.2.91.32 CMC is used as the gelling agent for AB 57 and HPMC in Wolbers resin soaps and enzyme
cleaning systems. Wolbers 1990B. pp.148.
33 Hone 1987, pp.129.
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the solubility of aged materials is well documented for easel paintings,34 however
little or no work has been carried out in the field of wall paintings. The physical
problems of the solubility of aged polymers would almost certainly be complicated
by the intimate contact with the dense crystalline matrix encountered with a porous
wall painting. To simulate such a situation on a model would be extremely difficult.
The major disadvantage encountered carrying out the tests on actual paintings is the
reduced level of chemical control that can be exercised due to the complex nature of
the painting itself. The interaction of materials on a wall painting that has
undergone restoration is difficult to understand without a full knowledge of the
constituent parts of both painting and previous treatment. For this study sufficient
knowledge of the present state of these materials was needed to clearly define the
effects of the gel tests. To overcome this problem it was necessary to carry out
detailed analysis of the paintings in their present state, before any tests were begun.
The choice of paintings was intended to encompass a sufficiently wide range of
dates, techniques, and previous restoration treatments in order that the project
should give a representative view of how the gels perform in a range of different
situations. The decision to carry out the tests on a number of such sites introduced
an additional series of variables, such as state of conservation and interaction
between multiple previous treatments, that should be considered when examining
the results of each individual series of tests.
The three sites chosen ranged in date from the 12th to the early 15th centuries and
varied in painting technique with both organic and inorganic media.
34 Mills and White, 1987.
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6. Test Methodology and Procedure*
The intention of using the solvent gels was to dissolve a single specific layer of
material on the painting. In order that the components of the gel were tailored to
this layer it was necessary to have a certain knowledge of the nature of the
particular material to be dissolved.
6.1 Examination and Analysis
Initial examination of the surface coating was carried out on site under low
magnification using normal and ultra violet illumination. Under UV by examining
the colour and intensity of the fluorescence, it was possible to distinguish in detail
the variations in nature and thickness of the coating. Such information was
important in establishing where samples were to be taken, and in identifying any
anomalies that might occur during the examination of particular samples.
Two types of samples were taken. Cross-sections of the painting were taken for
examination with optical microscopy, scanning electron microscopy (SEM) and
energy dispersive X-ray analysis (EDX).35 Samples of the individual surface coatings
and samples of pure materials to act as controls36 were taken for analysis by Fourier
transform infrared reflectography (FTIR)37 and Thermomicroscopy.38
In order to establish the solubility parameters of the surface coatings, standard
solvent tests were carried out using free solvents. This established broadly, the types
of gels that should be tested on each site.
35 Cambridge Stereoscan 200.36 Spectra were obtained from Ethomeen C-12, Carbopol 934 and 940, and BDH bleached beeswax.
37 Tests were carried out on a Perkin Elmer 1710 FTIR.
All FTIR analysis for this study was carried out in the Diffuse Reflectance Mode.38 Analysis was carried out on a Mettler FP800 hot stage, and samples were examined at a
magnification of xlOO.
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6.2 Preparation of Carbopol Gels.
To prepare the gels used in the tests the first stage was to calculate the solvency
parameters required to dissolve the coating. In order to do this a Teas chart was
prepared with the solvency parameters of both the major solvents and the solutes
plotted over each other.39 The overall solvency parameters of each solvent mixture
was then plotted, giving a clear visual representation of the areas in which the work
was to take place, allowing fine tuning of particular gels to be undertaken with
greater ease.
The two main criteria for the gels are the viscosity and the solvency parameters of
the solvent mixture. A neutralising amine should be chosen that forms a salt with
the Carbopol that is soluble in a solvent with the required solubility parameters.
Certain further solvents can be added at a later stage in order to adjust the overall
solvency parameters of the gel. The order in which the materials are combined was
established through a series of empirical tests and is an important to achieve a
successful gel.
1. principal solvent.
2. Carbopol.
3. Amine.
4. Polar solvent.
5. Secondary solvents.
During the whole process there should be constant agitation of the mixture to
ensure that the individual materials are sufficiently dispersed throughout the system.
First the Carbopol is evenly dispersed in the principal solvent. Then the amine is
added to form the salt necessary for the uncoiling of the Carbopol. Initial gelling
occurs at this stage. Since sufficient viscosity is an important property of the cleaning
agent extensive testing was undertaken to examine how the degree of viscosity could
be enhanced. Increasing the amount of Carbopol had little effect apart from bulking
39 The nature of the solutes had first been determined by analytical means. (See below under 6.2).
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out the solution. However the addition of small quantities of a polar solvent was
particularly effective. Therefore on the basis of empirical observation the procedure
was modified to include the addition of a polar solvent (normally water) at this
stage. This produced a suitably viscous gel to which could be added the secondary
solvents necessary to achieve the correct solvency parameters.
The addition of the secondary solvents after the initial gelling had occurred was
found to be of utmost importance. If the secondary solvents were mixed with the
principal solvent before the addition of the Carbopol it was observed that the gelling
process often failed to occur. This appeared to be due to the fact that the salt
formed by the Carbopol and the amine has been specificly chosen for its solubility in
the principal solvent. The addition of the secondary solvent at this point may have
altered the solubility parameters of the mixture so that the dissolution of the
Carbopol would be partially or totally inhibited.
The following materials were examined for their suitability as gelling agents for non-
polar solvent systems, but were considered to be less suitable than Carbopol.
6.3 Test Procedure
The procedure for the gel test was the same at each site. The gel was applied by
cotton wool swab and left static on the surface for a recorded period of time. After
this it was gently moved around with the swab in order both to remove swollen
material from the gel/surface interface and to move fresh gel into contact with the
surface. At the end of this period the gel was removed with a dry swab and the area
of the test was thoroughly swabbed with the aromatic solvent base of the gel (white
spirit or xylene) in order to clear any residues of the gel. Finally the area was
swabbed with deionised water to remove any remaining residues. The area was
allowed to dry before further samples were taken in order to asses the level and
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effect of cleaning. In some cases an intervention layer of Japanese tissue was used
during the tests. This was removed before clearance was carried out. The result of
each test was used to determine which gel was used for the following tests.40
6.4 Clearance Tests
Analysis to establish whether the clearance procedure was successful in removing all
residues of the gels was carried out in two stages. Initially all samples taken after
clearance were examined with normal light and UV microscopy and SEM to see if
any deposits of residue could be identified. In order to undertake more detailed
tests it was considered most expedient to use a model rather than carry out the tests
on actual paintings. This was necessary primarily due to the relatively large size and
controlled nature of the sample required. It was expected that if a residue was
present, its volume would be extremely limited compared to the that of the overall
sample and FTIR analysis would be further complicated by the interference of high
background 'noise' from the inorganic material from the surface of the painting that
would make up the major component of the sample. To take samples of the
necessary size from actual paintings would be nether justified or practical.
40 Appendices 1 & 5.
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7.0 St. Marv and All Saints Church. Holcot.41
7.1 Introduction
There are a number of different painting schemes in the church, all of which were
coated with wax, possibly by E.W.Tristram42 who describes them in his 14th-century
volume.43 The area selected for the tests was part of the immense area of painting
(54 x 12ft) on the north wall of the north aisle said by Tristram to depict 'six
Apostles, one probably StJohn, bearing the cup, and another St.Bartholomew with
the knife;'.44 Although the paint layer is flaking in certain areas, apparently due to
the activity of soluble salts, a suitably sound and accessible area was found on the
lower part of the painting. The painting is simple and linear in style, and probably
dates from the early 14th-century.45 It is very medium thin but probably painted
with a combination of organic and lime media.46
7.2 Painting Condition
Initial examination of the painting on the North wall showed that the surface was
coated with a relatively thick homogeneous layer of a translucent waxy material.
This was covered with a large amount of what appeared to be surface dirt. UV
examination showed that the coating had a weak fluorescence, and losses due to
damage showed clearly. The condition of the paint layer varied considerably, with
some areas suffering severe flaking and loss. Much of this damage appeared to be
due to the decohesion of the upper part of the substrate causing the surface layer to
break up. This may well have been due to the movement and crystallisation of the
soluble salts within the wall rather than on the surface, due to the impermeable wax
coating. However, much of the painting was sound, and it was in such an area that
41 Appendix 8.42 The beeswax-based material found on the wall is consistent with Tristram's recipe of c.1926.
Appendix 1.
43 Tristram 1955, p.181
44 Ibid.45 Ibid.46 See section 7.3
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the tests were carried out.
7.3 Cross-Section Analysis and SEM.
The thickness of the coating varied in some areas, but it appeared that there was
only a single coating present. In cross-section under both UV and normal
illumination this appeared to be the case (PI. 1). On top of this coating there
appeared to be a thin layer of crystaline material, which was discrete from the
coating and did not penetrate it. Under SEM this material could be seen on the
surface of the sample over the soft coating that covered the paint layer in a thick
unbroken layer (PL 12). At a higher magnification of xl380 the material appears to
be some form of effluorescence over the surface of the coating (PI. 13). It was
however easily removed with a soft sable brush, suggesting that it may simply be an
unusually thick layer of ambient dirt that had settled on the soft surface coating.
In cross-section, the structure of the painting can be seen to be relatively simple.
Above the plaster (not shown in the cross-sections) are two layers of tinted
limewash of varying thickness. In areas of background the limewash would have
formed the original paint surface over a lime ground. In figurative areas there is a
pigment layer over a single limewash ground. Media stains were carried out on a
number of samples, but the only positive result was achieved with Acid Fuchsin
which weakly stained the upper part of the limewash and pigment.47 This suggests
that for the limewash ground a small amount of protein was used as an additional
binder in what is mainly a calcium carbonate matrix. This relatively porous matrix
can be seen in SEM under relatively low magnification on the lower left hand side
of PL 12. The paint layer is very fine with a dense pigment content, and
identification of media by staining did not prove conclusive, however it appears
possible from the other analysis that an proteinous binder was used.
47 Acid Fuchin 2% vol/vol in deionised water. Rinsed with deionised water.
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7.4 FTIR and Thermomicroscopv
Samples of the coating were taken for organic analysis from two areas on the edge
of a large loss, where there was enough depth to avoid contaminating the sample
with large amounts of inorganic material from the surface of the painting. With
FTIR both samples produced similar spectra,48 showing that the majority of the
sample consisted of beeswax.49 This interpretation appeared to be confirmed by the
results of Thermomicroscopy which showed that the coating had a melting point of
approximately 64°C.
7.5 Solvency Parameter Tests
The free solvent tests carried out showed that the coating was readily soluble in a
range of aromatic and aliphatic hydrocarbons. A large part of the surface coating
was removed using xylene, without any apparent damage to the paint surface below
which appeared to be insoluble in the solvents.
7.6 Solvent Gel Tests
Solvent gel tests showed that the most effective cleaning action was achieved with
gel 7.50 Clearance was carried out with xylene and water. The optimum application
time was 20 seconds stationary on the surface followed by 60 seconds agitation with
a swab.51 SEM analysis of sample HO9/567 taken from this area show that the gel
had achieved a considerable level of thinning to a consistent level over the surface
of the sample (Pis. 14 & 15). This shows that there is still a fine film of the wax over
the paint surface, but that it is so thin that the material on the paint surface is
breaking through. PL 16 also clearly shows the limited level of penetration of the
wax coating and it would appear that a longer application of the gel would be
48 Appendix 5.49 persxomm. M.Odlyha and R.White.
50Apendix3.51 Appendix 8.
-31-
necessary to achieve complete removal.
Tests with gel 7 were also carried out through an intervention layer of fine Japanese
tissue for a period of 70 seconds. The effect of this was to considerably reduce the
amount of mechanical action on the surface of the paint film. During the period of
application less of the coating material was removed from the surface than without
the intervention layer, the majority of the cleaning action occurring when the tissue
was removed and the area swabbed with xylene. This appeared to lift off the heavily
swollen organic coating, with very little mechanical action necessary. Two
applications of the gel were necessary over an intervention layer to obtain the same
level of cleaning as a single direct application. The level of mechanical action on the
surface was however considerably reduced. This appeared to be confirmed by SEM
which shows a similar level of cleaning to that seen in Pis. 14 & 15. The SEM also
suggested that there were no significant residues of the gels present on the samples.
The wax coating was readily soluble in aromatic solvents in either a gelled or free
state and the best level of cleaning achieved by the gels in these tests was slightly
greater than that achieved with free solvents. The advantages of using a gel was the
dramatic reduction in mechanical action necessary to achieve the results and the
homogenious nature of the removal of the wax coating. The area on which the tests
were carried out was relatively sound, however much of the painting is in a far less
stable condition, and such a reduction would minimise the risk of damage to the
paint surface during cleaning.
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8. Holv Sepulchre Chapel. Winchester Cathedral,
8.1 Introduction
The earliest of the three sites is the Holy Sepulchre Chapel in Winchester
Cathedral. This contains two schemes of painting, the earlier of which dates from
between 1175 and 1185 and the later, from c.1220.52 Until the 1960s the only visible
part of the 12th-century painting was that situated on the south wall of the west bay,
depicting the Resurrection of the Dead. The main area of the earlier scheme,
situated on the east wall, was revealed in 1963 during work carried out by Mrs. Eve
Baker and her assistants. The 13th-century scheme, depicting the Entombment and
the Resurrection of Christ, was detached to reveal the very fine earlier painting of
the same subject.53 The newly revealed areas of 12th-century painting survived in
remarkably good condition, despite the heavy keying marks inflicted when they were
covered by replastering for the 13th-century scheme.
8.2 Technique
While the 13th-century paintings have always been assumed to be in a secco
medium, the appearance of the 12th-century paintings has suggested that they are in
fresco technique.54 The discovery under the 13th-century painting on the south wall
of the east bay of part of a 12th-century sinopia overlayed with a small area of
painted intonaco depicting the head of a male figure, suggested that the technique
was very similar to the Italian buon fresco technique, as described by Cennino
Cennini in his Libro dePArte. Recently, analysis undertaken on areas of the painting
on the east wall has shown that the technique is more complex than has so far been
assumed. Pigments not commonly associated with the boun fresco technique such as
red lead and vermilion were identified, suggesting a combination of both organic
and inorganic media.55
52 Park 1983, pp.53 & 4853 Ibid., pp.3854 Park 1983 pp.40
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The technique on the west bay of the south wall appears to be somewhat different.
Analysis of sample HS6/530 taken from the black outline of one of the angels flying
down to take up a resurrected soul again showed a thin layer of coating with small
wax residues on the surface; more importantly however it showed that this area of
painting is not in the same technique as the area in the east wall. Deep losses on the
painting reveal that there is only a single layer of plaster in this area. On this is a
layer of limewash on which is painted the under-drawing in a red pigment. Over this
is not an intonaco, but a second layer of limewash over which is painted the final
outline of the figure in carbon black apparently with a lime binder (PI .6). Further
examination of the painting confirms that this is the case, as in areas where the paint
surface is lost the red underpaint is clearly visible under a limewash and not an
intonaco.
8.3. Conservation History
The early restoration history of the paintings is undocumented, however it appears
from analysis carried out in the course of this project, that all the areas of painting
visible before the most of restoration in the 1960s were treated with one or in many
cases two layers of organic 'preservative' coatings. E.W.Tristram is thought to have
worked on the paintings which are documented in his volume on the 13th-century56
published in 1950 and it can be assumed that it was he who applied the upper (wax)
coating over a previous varnish layer, however the exact date of its application is
unknown. In 1959 The Eve Baker Trust began a program of restoration that
continued until 1970.57 It was during this period that the 13th-century paintings on
the east wall were detached to reveal the very fine 12th-century paintings below.
During this period also, work was carried out on the 12th-century scene of the
55 Hluvko 1991.
56 Tristram 1950
57 Baker 1964,1967,1970.
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Resurrection of the Dead on the south wall of the west bay. A certain amount of
cleaning took place on the coated areas, probably with Nitromors or a homemade
mixture based on this formulation58, and an area of 13th century painting on the
right hand side of was removed to uncover a well preserved figure of a trumpeting
angel of the earlier scheme.59
The 12th-century scene of the Resurrection of the Dead (with the exception of the
recently uncovered angel) is therefore unique in the chapel in terms of conservation.
It is the only area of the 12th-century painting to be exposed at the time of the early
restorations, and so it is the only area of predominantly lime bound painting to have
been coated with organic preservatives. This area of the painting was therefore
selected as a suitable site to carry out the solvent gel tests.
8.4 Painting Condition
The initial examination of the area of 12th-century painting to be tested in the Holy
Sepulchre Chapel showed that it was unusually dark for a wall painting treated only
with a wax-based material. Under low magnification a thin layer of coating could be
seen, the surface of which was covered with a number of residues as well as normal
surface dirt. One of these residues, which appeared to have been left in circular
patterns consistent with wiping action, was distinct from the surface, with a white
papery texture and a bright whitish fluorescence under UV illumination.
Examination of the rest of the area under UV illumination showed that the organic
coating, although very thin, was fairly homogeneous being broken in a few areas by
later damage. The only exception to this was in deep interstices or small losses,
58 Pers. comm,, David Perry.59 This area had previously been ignored by past restorers as it had been covered by a spiralstaircase inserted at the request of Samuel Wesley during his time as organist at the Cathedral(1849-1865), to enable him to reach the organ loft more easily. The staircase was removed andbroken up in 1938, pers. comm. John Hardacre. This revealed a badly damaged area of 13th-centurypainting that was detached in the 1960s restoration by the Eve Baker Trust, to reveal the 12th-century angel, pers.comm. David Perry.
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where the coating was thicker. Here it fluoresced slightly differently to other areas
with a weak greeny/yellow tint. Samples were taken from these areas for analysis as
they were the only areas with sufficient material available for FTTR analysis. The
condition of the paint surface below the coating is varied. In some areas there is
considerable flaking, some of which appears to be relatively old, but some is more
recent, suggesting that the damage in this case is active. There are also widespread
losses of the paint surface, revealing the red under-drawing below, however the
majority of these appear to have occurred before the application of the surface
coating.
8.5 Cross-Section Analysis and SEM.
Visible light microscopy clearly showed a fine translucent layer of material over the
surface of the painting (Pis. 3 & 5). Under UV illumination this layer had little or no
fluorescence, however in this light source it was possible to see isolated areas of a
second fine layer on the surface which fluoresced differently, being slightly brighter.
This layer was very fine and broken and was just discernible in visible light at a
magnification of x400. With SEM this material can be seen on the surface of sample
HS5/529 as a disrupted residue incorporation surface dirt that obscures the crazed
surface of the more homogeneous coating below (Pis. 17 & 19). The SEM clearly
illustrates the way in which the lower organic coating penetrates the porous matrix
of the lime-bound pigment (PL 18).
8.6 FT1R and Thermomicroscopy
The FITR spectra of the samples of the surface coating obtained from the
interstices showed that the majority of the material in the samples was beeswax,60
contaminated with large amounts of inorganic material, possibly from the paint
layer. No further organic material was apparent.61 These results were further
60 Appendix 5.
61 Pers. comm. M.Odlyha and R.White.
-36-
supported by Thermomicroscopy which showed that the coating had a melting point
of approximately 64°C. These results in combination with those described in 8.5
suggest that the material analysed here was not the coating now generally visible on
the paint surface, but the remains of a second more recent coating. It appeared
therefore that until the 1960s there had been two layers of organic coating on the
paint surface,62 and that the upper one of these, the beeswax, had been partially
removed at this time leaving the thin wax residue on the surface of the earlier hard
coating, but remaining in quantity in interstices or damages. This may also explain
the presence of the other Vhite papery' material found on the surface which may
well be the residue of the cleaning agent used at that time. FTIR analysis carried
out on a sample of this material, indicated that it was possibly some form of
cellulose.63 This was also suggested by Thermomicroscopy which showed the
material charring at approximately 250°C.
8.7 Solvency Parameter Tests
A range of solvent tests was carried out to establish the solvency parameters of the
coating, however the results were limited. Strongest solvency was in the region of
the aromatics, but it was observed that after an initial removal of a small amount of
material (probably beeswax) no further action took place.
8.8 Solvent Gel Tests
The results of the gel tests appeared to confirm the observations made with visual
62 David Perry, of the Perry Lithgow Partnership, and former conservator with the Eve Baker Trust,confirmed that this is probably the case. He carried out much of the work in the chapel during the1960's program, and said that he came across a second coating under the wax that was impossible to
remove in certain areas. He felt that it may have been a resin varnish.63 It was thought possible that the material was a residue of the cellulose part of the gelling mediumof the paint remover Nitromors (Celacol MMPR1) that may have been used as a cleaning agent inthe 1960s intervention. Celacol MMPR1 was produced by Courtaulds Ltd. It is however no longerin production and an infra red spectra of the material was not available. The material producedtoday considered to be the closest chemically to Celacol MMPR1 is Celacol HPMMPR1, anhydroxypropyl methyl cellulose (pers.comm. Dr.N.G.Todd). IR spectra of this material, comparedone from the Winchester sample (KMHS2) showed similarities in diagnostic frequencies,
suggesting that it was a similar cellulose material. Appendix 5.
-37-
examination and analysis. The optimum effect was obtained with gel 7 applied for
10 seconds static and moved for a further 60 seconds.64 Clearance was then carried
out with xylene and water. The cleaning was very limited and similar in effect to that
achieved by the aromatic free solvents applied in the tests to establish solvency
parameters. A small amount of material including dirt and residues of the upper
wax layer on the surface of the coating were removed, but the lower resin coating
appeared to remain unaffected.
Analysis of sample HS7/571 taken from the area of this test would appear to
confirm that the residues of the wax layer had been removed leaving the lower layer
untouched. In cross-section at magnification up to x400 the lower layer was clearly
visible over the pigment surface (PL 4), and under UV the remains of the upper
layer were no longer visible. This was further shown by the SEM examination of the
surface of the sample (Pis. 20 & 21). Comparing this to the surface of sample
HS5/529 before cleaning (PL 19), it is apparent that the disrupted material on the
surface has been completely removed, while the lower layer remains in tact.
Clearly the gel is working efficiently and thoroughly on the material for which it was
designed. The earlier resinous layer should be further analysed in order to establish
its exact nature, and a second cleaning system should be designed to remove it.
64 Appendix 2.
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9. Westminster Abbev Chapter House.
9.1 Introduction
The Chapter House of Westminster Abbey has a complex history and the survival of
the paintings on its walls is remarkable considering the number and scope of
interventions that have occurred. The paintings, depicting scenes from the
Apocalypse of St. John were probably carried out sometime between 1372 and 1404,
and are of the highest quality.65 Each side of the octagonal Chapter House, except
for the west entrance wall, contains five bays separated by Purbeck marble
arcades.66 The condition of the individual areas of painting varies according to that
of the ashlar masonry support, and the type of previous restoration. The only
internal wall is the north west (side 1), and here not surprisingly, the paintings
survive in the best condition.
The Chapter house was built by Henry III from c.1245-1255, and was apparently
intended from the outset to serve an additional function as a secular meeting room.
The Great Council met there in 1257, and it was a frequent venue for parliament
until 1547. From the dissolution it served as a store for public records, and the
provision of a gallery and book-shelves against the walls caused a certain amount of
damage to the architecture. The first restoration was carried out by George Gilbert
Scott from 1866-73.
92 Technique
The painting are carried out on a white ground directly over a substrate of tooled
closely jointed ashlar masonry the shows through paint layer. The paint layer itself is
complex with a number of different pigment layers and surface glazes,67 with
pigments of the highest quality.68 It would appear likely that there would have been
65 Turner 198566 Numbering of the 7 sides is carried out clockwise from the entrance.
67 Hluvko 1991.
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an original varnish, however this is no longer visible.
9.3 Conservation History
The conservation history of the paintings, although better documented than in most
cases, is complex and unspecific in the location of particular treatments.
9.3.1 G. G. Scott
The first recorded treatment to the paintings was probably carried out under Scott.
The exact date and method is not recorded, however references to the paintings in
his book of 1863 throw some light on the subject.69 Scott refers to his discovery of
the paintings behind the bookcases that had obscured them and agrees with
Eastlake that they date from the mid 14th-century and with his suggestion that the
medium is oil.70 Although Scott does not refer to treatment of the paintings, he does
describe the treatment of the stone tympanum over the entrance. This was first
cleaned with a soft jet of air, and then injected with an (unspecified) solution, the
effect of which was to harden the decayed stone. It is possible that a similar
treatment might have been used on areas of painting where the stone support was in
the same condition as the tympanum. The only direct reference to Scott's treatment
of the paintings is by Prof. A. H. Church who in his report of 1904 refers to the
difficulties he had treating the paintings in the North West arcade, which he said
that Scott had varnished.71
9.3.2 Prof. A. H. Church
Church himself carried out work on the paintings between 1901 and 1903. In his
report of 1904 he claims that the damage to the paintings was due mostly to the
68 Hluvko 1991 and Howard 1988.69 Scott 1863, pp. 40-43
70 Eastlake 1947. pp.571 Church 1904
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attack on the stone by the 'acidic atmosphere', which not only broke down the weak
structure of the stone, but introduced further soluble salts to the paintings. In his
analysis Church discovered that as well as chlorides, the stone contained large
quantities of sulfates, the source of which he thought to be atmospheric sulfur
dioxide. This had reacted with the calcium carbonate in the wall to form larger and
water-soluble calcium sulfate crystals, causing the breakdown of the cohesion of the
stone, resulting in the damage to the paintings. To counter this Church treated the
paintings with baryta water applied six to twelve times in order to introduce enough
barium hydroxide into the wall for the treatment to prove effective.72 This in turn
introduced a large amount of water into the wall which Church had himself
acknowledged was causing damage due to the mobilisation of soluble salts.
9.3.3 H.M.Office of Works
The third treatment took place in 1929 and is recorded in an anonymous article in
the Museums Journal of that year which mentions that in many of the bays there
was a severe deterioration of the stone and that the paintings had a uniformly gray
appearance.73 This could have been due to the barium carbonate bloom which
Church himself acknowledged as a possible consequence of the 1901-03 baryta
water treatment.74 To fix, consolidate, and restore the aesthetic quality of the
paintings, a coating of bleached beeswax dissolved in turpentine with 2% linseed oil
was applied to the paintings.75 Flaking paint was readheared by injecting this
solution behind the paint layer with a syringe and pressing the flakes back by hand.
Consolidation of friable areas was carried out by spraying the solution onto the
72 Baryta water is an aqueous solution of barium hydroxide. The theory behind the treatment was
that calcium sulfate crystals would be converted into the more stable and insoluble barium sulfatecrystals. This would leave calcium hydroxide which would reconvert to calcium carbonate with
atmospheric carbon dioxide.1. CaSO4 + Ba(OH)2 -> Ca(OH)2 + BaSO4
2. Ca(OH)2 + CO2 -> CaCO3 + H2O
73 H.M.Office of Works. 1929, pp.376
74 Church 1904. pp.575 The same mixture without the turpentine was applied in some areas with the use of heat
administered by a baffled blow torch.
-41-
surface and then encouraging its penetration with the use of a paraffin blow torch
fitted with a baffle.76
9.3.4 English Heritage
The most recent treatment was carried out in 1985 by English Heritage, when the
paintings on the north west side were cleaned and the coating (there was only a
single wax coating on these paintings) removed with a mixture of 80% White Spirit
and 20% Propan-2-ol. At at the same time a partial cleaning was carried out on all
the other paintings in the Chapter House. This was undertaken using a hot-air
blower to melt the wax on the surface, which was then removed with large cotton
wool swabs.77
9.4 Painting Condition
The initial examination showed that the surface was very uneven and broken in
some places and that areas of the paint surface were seriously disrupted, apparently
due to the damaged stone support. There were areas where serious flaking had
occurred in the past, but all of these had been coated and consolidated with the
waxy coating. The overall condition of the painting was therefore sound in that no
active damage was occurring, however the true state of the painting below the
coating was far less solid. It was clear that more than one coating was present, but
the exact limits of each layer was difficult to establish. Under UV it could be seen
that there were two dominant coatings. The upper one appeared to be a soft waxy
material, and was very thin in some areas. Towards the edge of the painting where it
was protected from the 1985 partial cleaning by the pillars this coating is far thicker,
up to lmm in some areas, suggesting that the majority of the material had been
76 During the process a certain amount of the old varnish was removed. This was usually carried outwith a mixture of methelated spirits, benzene or turpentine, however where the material proved
particularly hard to remove, pyridine (C5H5N) was used. H.M.Office of Works 1929. pp.376.
77 Pers. comm. J. Keevil, Head of the English Heritage conservation studio.
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removed in the 1985 treatment. Beneath this layer was a second coating, consisting
of a thick layer of a hard dark resinous material. Both layers were heavily
contaminated with paniculate material, apparently a combination of ambient dirt
and material from the paint surface.
9.5 Cross-Section Analysis and SEM.
Samples were taken in most cases from sections of white pigment on and around the
scroll in the center of the area in an attempt to obtain similar layer structure to
facilitate comparison in the cross-sectional analysis. In practice this failed to occur
due to the severe damage and the complex nature of the painting which was further
confused by the effects of earlier restorations. It was clear from all the samples that
there were two separate surface coatings as had been expected. The upper coating
was very fine in some areas, and had very little autofluorescence under UV
microscopy. Under SEM this layer had a soft feathery appearance characteristic of
wax (PL 24),78 and although thin was fairly homogeneous over the paint surface.
The lower layer fluoresced with a yellow/green tinge under UV and was relatively
thick. Under SEM it was possible to see the hard fractured edges typical of a natural
resin varnish. The interface with the paint surface was very disrupted with what
appeared to be material, possibly salts, effluorescing through the paint surface itself
(PL 7).
9.5.1 Binding Media
The structure of the painting itself was immensely complex with up to six often
discontinuous layers present in the same sample. On a number of the samples taken
from the edges of more prominent losses, the lowest layer (above the stone
substrate) consisted of the same wax material to be found on the surface. This
showed how the wax had been used as both fixative and consolident, and was
injected behind such loose edges in order to readhere them as explained in the 1929
78 pers. comm. Aviva Burnstock.
-43-
report and is apparent in PI. 10.
The nature of the medium of the painting is of obvious importance when
establishing the solvency parameters of the gels. Past analysis79 and the survival of
records regarding the purchase of large quantities of oil80 appeared to suggest that
the predominant medium was indeed oil. In order to confirm this, stain tests were
carried out with Sudan Black B,81 Acid Fuchsin,82 and the fluorochrome stain for
lipids, Rhodamine-B.83 The Sudan Black failed to stain the apparently medium-rich
pigmented layers, but took strongly to the thick lower layer of the coating. Acid
Fuchsin only stained in a single case when it took to two small isolated areas on the
lower side of the sample, suggesting that protein was not commonly present, and
that these two areas were anomalous. Under UV the Rhodamine-B was seen to
have stained the central pigment layer, which appeared to be the most medium rich,
a light purple indicating the possible presence of lipids. The stain was far too weak
in this area to suggest the presence of any large quantity of oil, but was stronger on
the bottom of the sample where an area of wax appeared to have penetrated behind
the paint surface (PL 9.).
9.6 FTIR and Thermomicroscopy
Samples taken of both surface coatings were examined with FTER and
Thermomicroscopy in order to further identify and differentiate between the two
layers.84 The resulting spectra had diagnostic frequencies clearly showing the
presence of beeswax in both samples,85 and neither contained any peaks that
79 Howard 198880 Eastlake 1847. pp.49-5581 Sudan Black, a saturated solution in IMS. Rinsed with IMS.
82 Acid Fuchsin 2% vol/vol solution in deionised water. Rinsed with water.
83 Rhodamine-B. 0.02% vol/vol solution in IMS. Rinsed with IMS.84 To enable a larger volume of sample to be gathered, they were taken from the edge of the
painting, where less of the upper layer had been removed in 1985.
85 Appendix 5.
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indicated the presence of an organic resin. Thermomicroscopy showed that the
samples had a melting point of approximately 64°C, also indicating the presence of
beeswax. The conclusion to be drawn from these results is that the resin layer which
is clearly visible in SEM and visible microscopy failed to be collected in the sample.
Both samples were heavily contaminated with what appeared under low
magnification to be dirt, resulting in the high level of background noise on the
spectra.
0.7 Solvent Parameters Tests
The area of painting chosen for the gel tests was in the third (central) bay of side 6.
Although much of the painting in this bay is severely damaged, the area in the lower
right hand scene appeared to be reasonably well preserved beneath its coating of
dark wax and resin. A range of solvent tests showed that the upper coating was most
soluble in the aromatic region, with a mixture of xylene and benzyl alcohol in the
proportions 2:1 having the strongest effect. None of the tests appeared to have any
effect on the lower resin layer.
9.8 vSolvent Gel Tests
Due to the lack of solubility demonstrated by the resin layer in the earlier solvent
tests it was felt that tests with aromatic solvent gels could take place on the upper
wax layer without affecting the lower layer.
As with the Holcot and Winchester tests, the most successful cleaning was achieved
with gel 1J86 Applied for 105 seconds in all and cleared with xylene and water, this
successfully removed the upper wax layer while leaving the lower resin layer
apparently untouched. Using SEM this can be seen on sample WA8/558, leaving
the smooth resin surface and the pigment layers below (PL 25). In order to remove
the resin layer two resin soaps developed by the National Gallery Scientific
86 Appendix 2.
-45-
Department, and described in the 1990IIC Brussels conference,87 were tested on
areas already cleaned with gel 7. The 9-fluorenone-4-carboxylic acid soap (9FOC),
applied for 120 seconds, and cleared with xylene and water appeared to have little
or no effect on the material. The Anthracene-9-carboxylic acid soap (A9C), did
appear to have some cleaning effect. Also applied for 120 seconds, and cleared with
xylene and water, the effect was noticeable even at low magnification. Under SEM
the cleaning action is more apparent. The surface of WA14/564 (PL 26) shows that
the soap had significantly thinned the resin without disrupting the paint layer by
undercutting. Examination under UV illumination appeared to show a bluish
fluorescence in the area of the A9C test; none was seen in the area of the 9FOC
test. As the A9C is not known to be autofluorescent, it is possible that the apparent
fluorescence was due to the materials of the painting rather than those of the
cleaning reagent.
10. Analysis for residual materials
It was clear from both visible microscopy and SEM that at the three sites where tests
were undertaken that the majority of the gel was removed from the paint surface,
and that any residues that may remain would be relatively small. With the type of
organic analysis available, the size of sample necessary to obtain a volume of
residue that was identifiable would have to be relatively large. It would have been
impossible to take such samples from the surface of the test paintings, and so it was
necessary in this case to use a studio model. This had the added advantage that the
materials could be controlled, thus avoiding the contamination with unknown
materials that samples taken from actual paintings would be likely to have and that
could mask the results.
87 Burnstock and White 1990.
-46-
The model was a small block of approximately 3.5cm sq., constructed of two layers
of plaster, an arriccio with a large aggregate, and a thin lime-rich intonaco (pi. 11).
The surface was painted in buon fresco technique with yellow ocher. The block was
made and painted in 1988, and so the lime would have been well carbonated at the
time of the tests. Three weeks before the tests were carried out, half of the surface
of the block was treated with a wax-based mixture typical of the type used by
Tristram during the second quarter of this century.88 The day after application this
was polished with a dry cloth as was recommended.
Before the gel tests were carried out surface scrapings were taken from both the
waxed (KSR 1) and unwaxed surface (KSR 3). In both cases the sample area was
about lcm sq. The samples were intended to contain all components that might
contaminate a sample taken after testing, this included pigment, calcium carbonate,
surface dirt and in the case of KSR 1 the wax coating. Gel tests were carried out on
both areas with gel 7, as this had been the most successful gel on the site tests, and
cleared with xylene and water. Similar samples were then taken on the waxed (KSR
2) and unwaxed areas (KSR 4) after testing. In the latter case small amounts of wax
were removed from the interstices around the edge of the gel test area, as it was
important to establish whether residues were left in the coating itself.
FTIR analysis was then carried out on all four samples as well as on samples of
Carbopol 940 and Ethomeen C-12, the non-volatile components of the gel.89 None
of the diagnostic frequencies of the Carbopol or the Ethomeen could be seen on
either spectra obtained from the after cleaning samples (KSR 2 and KSR4) however
in some cases this could be due to masking by another peak. This result is
encouraging, but as it is in effect uncalibrated it does not mean that the residues are
definitely not present. It would be necessary to conduct a series of tests to obtain an
88 Appendix 1.89 Appendix 5.
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internal standardisation for these results to show positively that the samples
contained no residue from the gel.90 Further analysis to establish the presence of
residues could be carried out using secondary ion mass spectroscopy which would
prove more sensitive for low concentrations than the FTIR.
11. Conclusions and Further Research.
It appears that the use of a gelling medium contains, and, in effect, enhances the
action of a particular solvent in terms of the amount of the solute dissolved over a
given period of time. This is apparently due to the gelling medium reducing the
speed of evaporation of the solvent thus allowing it a longer and more intimate
period of contact with the solute. The gel medium will therefore have a greater
effect enhancing the action of highly volatile solvents, than those with relatively low
rates of evaporation which would, in their free state, remain in contact with the
solute for a longer period of time.91 This enables one to use a relatively inefficient
solvent in a gel to perform the work of a 'stronger' free solvent. Therefore a
material only partially soluble in a certain solvent could more efficiently be
dissolved using the same solvent in a gel system. This reduces the risk to other
materials with similar solubility parameters to the desired solute that may be
effected by the use of a 'stronger' free solvent that may traditionally have been used
to remove the main solute. The results of this and earlier work demonstrate that it is
90 A series of tests could be carried out decreasing the volume of the gel in a standard sample untilit no longer registered on the FTIR. This would establish a base-line for the detection of residues
which could be related to the results obtained in the present tests.
91 To verify such an hypothesis a series of tests could be undertaken with two solvents of similar
solvency parameters but different rates of evaporation. Both solvents would be applied first in their
free state and then in a gel for a set period of time. The resulting dissolution of the solute could
then be measured for both tests in terms of how much material had been removed and the resultscompared to establish in terms of percentage gain ('gain' would be considered to be an increase inthe material removed from the solute), whether the highly volatile solvent had increased its effect
more that the low volatility solvent.
-48-
possible to produce a variety of gels with a wide range of solvents, both polar and
non-polar, allowing extreme flexibility and the adaptation a particular gel to deal
with a specific problem.
The health and safety implications are clear. The gels system by reducing the
evaporation of the solvents reduces the volume of solvent released into the air in
contact with the conservator. The choice presented by the wider range of solvents
available in a gel system able to dissolve the same material also allows the use of
less toxic solvents.
Empirical observations made during the gel tests at Holcot using an intervention
layer give a further important insight into the working method of the gels. It appears
that rather than completely dissolving the wax and absorbing it into the body of the
material, the gel is simply swelling it to a high degree, and the mechanical action of
the swab is removing the wax in its swollen state from the active interface between
gel and coating. It is clear then that mechanical action although significantly less
than that involved in traditional solvent cleaning is an integral part of the solvent gel
cleaning process, not only removing the swollen material from the surface, but also
replacing the gel at the interface with a fresh solvent-laden gel enabling the process
to continue. Surface characterisation of cleaned areas with SEM, suggests that the
action of the gels is one of thinning the coating from the surface down rather than
swelling and dissolution as might occur with the use of free solvents. The effect of
this is to allow far greater control to be exercised over the level of cleaning.
Although many of the results of this project are encouraging in regard to the use of
solvent gels for the cleaning of wall paintings, it must be regarded as part of a larger
long-term study. There are a number of areas which require further and more
detailed investigation. Most important among these is the clearance of the gels
discussed above in section 10. From SEM characterisation it is apparent that there
are no sizable residues of the cleaning reagent deposited on the surface of the
-49-
samples after clearance. However, it is necessary to establish by more specific
analysis, before the gels are used on any scale, that all the non-volatile material is
being removed. The analytical techniques most likely to identify the presence of
very small concentrations of the cleaning materials are gas chromatography with
mass spectrometry (GCMS).92
The effect of solvent gels on the paint layer is an area that has not been extensively
examined in the scope of this work, primeraly due to the nature of the particular
paintings tested. In two cases, there appeared to be no organic component in the
paint layer that would be effected by the gel, while in the third (Westminster Abbey)
the vulnerable paint layers were protected by the presence of the resin layer
beneath the wax that proved to be insoluble in the gels. Due to the nature of the
solvents contained in the gels, there is clearly a potential risk to certain organic
components that occur in many wall paintings. Further investigation should be
specifically aimed at examining such effects in order to establish more exactly the
action of the gels on such vulnerable materials.
A third area which requires further research is the effect that surfactants have on
the solubility parameters of certain solvents. The use of a surfactant allows a polar
solvent such as water to dissolve a non-polar material upon which, without the
surfactant, it would have no effect. It appears probable that this effect would occur
to a greater or lesser extent with all solvents combined with a surfactant. In theory
this could radically alter the accepted solvency parameters. As the gels discussed in
this project all contain a certain amount of material with surfactant properties, the
solvency parameters calculated in the standard manner may be affected in a way
that has not been predicted.
The use of solvent gels for removing wax coatings from wall painting clearly has
92 Burnstock and White 1990.
-50-
advantages over some of the 'traditional' methods. Most importantly it allows a far
greater control over the solvent parameters of the system, in effect making the
whole process more specific to the individual material to be removed thereby
reducing the risk to other soluble materials in the painting. The reduction in the rate
of evaporation of the solvents included in the gel is without doubt advantageous in
terms of health and safety to the conservator, as is the possibility of using less toxic
solvents in some cases. Further tests are necessary before these solvent gels can be
widely used, however the results to date show that they can be successfully employed
in certain cases.
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12.0 BIBLIOGRAPHY
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Cathedral Record, pp. 10-12.
Baker, E. and Baker R. 1967, 'Paintings in the Chapel of the Holy Sepulchre.',
Winchester Cathedral Record, pp.21-25.
Baker, E. 1970, 'The Holy Sepulchre Chapel, Winchester Cathedral.', Winchester
Cathedral Record, pp.29-31.
Ballantyne, A. et al. 1988, "The problems of dewaxing', Preprints for the UKIC 30th
anniversary conference. London, pp.135-41.
Bellamy, L. J. 1975, The Infrared Spectra of Complex Molicules. London.
Burnstock, A. and White, R. 1990, 'The effects of selected solvents and soaps on a
simulated canvas painting.'Cleaning. Retouching and Coatings. (Preprints of the the
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Cather, S. & Howard, H. 1986, 'The use of wax-resin preservatives on English
medieval wall paintings: rationale and consequences', Case studies in the
conservation of stone and wall paintings (Preprints of the IIC Bologna Congress),
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Central Council for the Care of Churches. 1959, The Conservation of English
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Care of Churches and the Society for the Protection of Aincient Buildings. London.
Church, A. H. 1901, The Chemistry of paintis and painting. London.
Church, A. H. 1904, Treatment of decayed stonework in the Chapter House of
Westminster Abbey. London.
Courtauld Institute of Art, Conservation of Wall Painting Department, 1990.
'Chapel of Our Lady Undercroft, Canterbury Cathedral. Report on Cleaning Tests
on the Vault and Screen', Unpublished.
Derrick, M. 1989, 'Fourier Transform Infrared Spectral analysis of natural resins
used in furnature varnishes.' J.A.I.C. 28. pp.43-56.
Eastlake, C. L. 1847, Materials for a History of oil painting. London.
Fletcher, K. 1988, 'The practical use of some flourescent dyes in the characterisation
of varnish layers in cross-section and the subsequent cleaning of some paintings
using the methods developed by Richard Wolbers', Unpublished, Courtauld
Institute.
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Getty Conservation Institute. 1991, Methods in Scientific Examination of Works of
Art: Infrared Microspectroscopv.
Goodrich, B. F., CAROPOL Water Soluble Resins. Technical data. Ohio.
Hedley, G. 1980, 'Solubility parameters and varnish removal; a survey.' The
Conservator 4, pp. 12-28.
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IIC, London.
H.M.Office of Works, 1929, 'Methods of preserving mural paintings in the Chapter
House of Westminster Abbey/ The Museums Journal, vol.28, no.12.
Horie, C. V. 1987, Materials for Conservation. London.
Howard, H. 1988, 'Blue Pigments in English Medieval wall paintings', Unpublished,
Courtauld Institute.
Hluvko, S. 1991, 'Red Pigments in English Medieval Wall Paintings', Unpublished,
Courtauld Institute.
Keyser, C. E. 1883, List of Buildings...having Mural...Decorations. London.
Low, M. J. D and Baer, N. S. 1977, 'Application of Infrared Fourier Transform
Spectroscopy to problems in Conservation. I. General Principles', Studies in
Conservation. 22.
Macregor, E.A ,Greenwood, C.T, 1980, Polymers in nature. London.
Meilunas, R.J, Bentsen J.G. and Steinberg A. 1990, 'Analysis of aged paint binders
by FTIR spectroscopy'.Studies in Conservation. 35. pp.33-51.
Mills, J. and White, R. 1987, The Organic Chemistry of Museum Objects. London.
Mora, L., Mora, P. and Philippot, P., 1984, Conservation of Wall Paintings. London.
Newman, R. 1980, 'Some applications of Infrared spectroscopy in the examination
of painting materials', J.A.I.C.. 19. pp.42-62.
Noppen, J. G. 1932, 'The Westminster Apocalypse and its source.' The Burlington
Magazine. Vol.61, pp.146-159.
Oakeshott, W. 1981, 'The Paintings of the Holy Sepulcre Chapel' Winchester
Cathedral Record, pp. 10-15.
Park, D. 1980, 'The wall paintings of the Holy Sepulchre Chapel' Medieval Art and
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Architecture at Winchester Chathedral. (British Archiological Assosiation
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Perry lithgow Partnership, 1983, Report on the wall painting in Holcot church.
Unpublished report.
Scott, G. G. 1861, Gleanings from Westminster Abbev. London.
Scott, G. G. 1863, Gleanings from Westminster Abbev. London.
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.37. pp.43-44.
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Paintings.' The Getty Conservation Institute. (Unpublished).
Appendix 1
Recipes for wax and wax resin preservatives advocatedbv Professors Church and Tristram.
A. H. Church. Published in Keyser (1883, xciii),
described as a 'preservative'.
2 oz. by weight pure white beeswax.
6 oz. by measure oil of spike
lavender or oil of orange peel.
10 oz. picture copal varnish.
26 oz. freshly distilled
spirits of turpentine.
Preparation; Melt beeswax, pour into the oil of spike;
warm until clear, then add copal and turpentine.
Application; warm with 'broad flat soft brush' or, if
colour 'easily detached, with spray.
Gambler-Parry. 'Simplified* by Church and
published in Church (1901:123), described as a
'medium*.
8 oz. oil of spike.
2 oz. by weight elemi.
2 oz. oil of turpentine.
4 oz. by weight pure white wax.
20 oz. by measure 'picture'-
copal varnish or 16 oz. oil-
copal varnish.
Preparation; Warm oil of spike over water to 80C,
add elemi and shake until dissolved; filter warm
solution; heat oil of turpentine over water to 80C;
mix thoroughly; heat over water to 80C, add melted
wax; shake thoroughly; add varnish with constant
agitation; allow water to boil under the mixture for 5
minutes, remove, dry and cool.
A. H. Church. Published in Church (1901:122 and
323-24), described as a 'preservative and medium'.
12 oz. of spike or non
-refinable oil of turpentine.
4 oz. by weight paraffin wax
(melting point 58-62C) or of
ceresin or a mixture of these.
20 oz. 'picture' copal-
varnish or 16 oz. oil-copal
varnish (containing a
sufficiency of oil).
Preparation; Warm oil of spike over boiling water,
add wax and mix thoroughly at 80C; add copal slowly
mixing constantly.
Application; Diluted with spirits of turpentine or
toluene.
E. W. Tristram, published in Tristram 1926,
described as a 'preservative'.
1 part beeswax.
6 parts by volume rectified spiritsof turpentine.
1% Unseed oil.
Preparation; Melt the beeswax and add the other
ingredients.
Application; lightly with a brush or, if the surface is
'too friable', dilute with more turpentine and spray
on. Polish lightly with a rag two or three times during
the following fortnight.
1.
Xylene
H2O
Carbopol 940
Ethomeen C-12
Propan-2-ol
69/9.3/21.72
3.
White Spirit
H2O
Carbopol 934
Ethomeen C-12
Propan-2-ol
71.6/9.3/19.1
5.
White Spirit
H2O
Carbopol 934
Ethomeen C-12
Propan-2-ol
Acetone
74.5/10.5/15
7.
Xylene
H20
Carbopol 940
Ethomeen C-12
Propan-2-ol
Acetone
68.7/13.4/17.9
9.
White Spirit
H2O
Carbopol 940
Ethomeen C-12
Propan-2-ol
76/8/16
11.
White Spirit
H2O
Carbopol 940
Ethomeen C-12
Propan-2-ol
Acetone
71.2/13.1/15.7
50ml
lml
lg7.5ml
10ml
50ml
lml
lg6ml
30ml
50ml
2.5ml
lg6.5ml
15ml
10ml
50ml
5ml
lg7.5ml
10ml
20ml
50ml
lml
lg7ml
20ml
50ml
lml
lg9ml
15ml
20ml
Appendix 2
Solvent gels formulae1
2.
Xylene
H2O
Carbopol 940
Ethomeen C-12
Propan-2-ol
76/7.2/16.8
4.
White Spirit
H2O
Carbopol 934
Ethomeen C-12
Propan-2-ol
Xylene
79.3/6.9/13.8
6.
White Spirit
H2O
Carbopol 934
Ethomeen C-12
Propan-2-ol
78.7/7.2/14.1
8.
Xylene
H2O
Carbopol 940
Ethmeen C12
Propan-2-ol
Benzyl Alcohol
69/9.4/21.6
10.
White Spirit
H2O
Carbopol 940
Ethomeen C-12
Propan-2-ol
Acetone
76.9/10/13.1
12.
White Spirit
H2O
Carbopol 940
Ethomeen C-12
Propan-2-ol
Benzyl Alcohol
77/7.7/15.3
50ml
lml
lg7.5ml
10ml
50ml
lml
lg6ml
15ml
10ml
50ml
lml
lg6.5ml
15ml
50ml
5ml
lg7.5ml
10ml
20ml
50ml
lml
lg7ml
10ml
10ml
50ml
lml
lg7ml
10ml
10ml
1 All solvents used were GPR quality except for the White Spirit which was manufactured by Langlowproducts Ltd. with an aromatic content of 15-25% v/v.* Solveny parameters: dispersion/ dipolar/ hydrogen bonding.
Appendix 3
Teas Chart showing the solvency parameters of the most effective solvent gels in relation tothe solubility region of beeswax.
10 20 30 40 50 . 60 70
Dipolar force
80
Solubility region of beeswax (Horie 1987)
Appendix 4
Solvent Gel Tests.
Summary of results reported in the proformas.
Holcot Church.
Test Gel Clearing Application Intev. Cleaning Effect,
no. no.1 Method.2 Time.3 layer.4 wax layer only.5 Sample.6
1. 7. Xylene/H20 10/30 + + + HO8/565 & HO8b/566
2. 7. Xylene/H20 20/60 + + + + HO9/567 & HO9b/568
3. 8. Xylene/H20 15/60 + +
4. 2. Xylene/H20 15/90 + + + HO10/568
5. 9. WS/H20 20/120 + + +
6. 7. Xylene/H20 10/60 * ++ HOll/569
7. 7. Xylene/H20 10/60 * + + + + HO12/570
Tests 6. and 7. took place on the same area.
Holv Sepulchre Chapel. Winchester Cathedral.
+ + + + HS7/571
+ HS8/572
Tests 1. and 2. took place on the same area.
Westminster Abbey Chapter House
+ + + WA8/558 & WA9/559
+ + + + WA13/563
+ + + WA1O/56O
15/120 + + +
Tests 4. and 5. took place on the same area.
1.
2.
3.
4.
5.
7.
7.
8.
11.
1.
Xylene/H20
Xylene/H20
Xylene/H20
WS/H20
Xylene/H20
10/60
10/60
10/90
10/90
10/90
1.
2.
3.
4.
5.
6.
7.
7.
7.
1.
1.
11.
Xylene/H20
Xylene/H20
Xylene/H20
Xylene/H20
Xylene/H20
WS/H20
15/90
0/120
15/120
15/90
15/90
15/120
1 Appendix Proformae
2 Solvent followed by water, both with cotton wool swab.
3 Static/agitation time in seconds.
4 Intervention layer of Japanese tissue.5 Key: + Little or no effect.
+ + Limited effect.
+ + + Partial wax removal.
+ + + + Substatial level of cleaning.
+ + + + + Complete removal of wax layer.
6 Samples HO8/565 and HO9/567 were taken before clearance with water.Samples HO8b/566 and HO9b/568 were taken after both xylene and water clearance was carried out.
Appendix 5
Fourier Transform Infrared Spectra.
All spectra were carried out on a Perkin Elmer 1710 FTIR in diffuse reflectance mode. Allspectra have undergone conversion to Kubalka-Munk units.
Fig.l. Holcot Church. Sample HO2. Waxy surface coating. (KMHO2)
NAX=1.48 T
fHff=8.32 T
3566 3860 2598 2698 1568 CH-1 1888
Fig.2. Holy Sepulchre Chapel, Winchester Cathedral. Sample HS3. Waxy surface coating.
(KHS3A)
-1728
1888 CH-1 588
II
Fig.3. Westminster Abbey Chapter House. Sample WA3B. Waxy surface coating.(KWA3B)
MftX=2.73 T
u
s
*l*/ v\
I
/\
! niN=e.32
i *rl i
-v,
4*88 3538 2508 2999 1588 CIM 1888
Fig.4. Westminster Abbey Chapter House. Sample WA2B. Lower resinous layer.(KWA2B)
=i.37 T
■839 3588 3888 2589 2988 1588 Cil-t
Ill
Fig.5. Clearance test model. Sample SRI.
Wax coating on panel before testing. (KSRl)
IM=7.07 T
11111=9.32 T
4909 3560 3660 2560 2090 1500 1096 Cll-l
Fig.6.Clearance test model. Sample SR2.
Residues of wax coating after testing. (KSR2)
6 3
4000 3586 3086 2590 2860 1586 1690 Cll-l 568
IV
Fig.7. Clearance test model. Sample SR3.
Paint surface before testing. (KSR3)
<=4,48 T
11111=9.32 T
4988 3589 3088 2588 2889 1508 16130 Cll-l 500
Fig.8. Clearance test model. Sample SR4.
Paint surface after testing. (KSR4)
3588 3908 2509 2888 1588 1088 CIH 599
Fig.9. BDH Beeswax, white. (Prod. 33017) (KMBW3)
4888 35
Fig.10. Ethomeen C-12 (KC12)
HIN=B.32 T-^ r
4808 3588
VI
Fig.7. Carbopol 940 (KC940)
Appendix 6
Nitromors Paint Stripper
'Nitromors' is produced by Henkel Home Improvements and Adhesive Products.
'Nitromors Original' was introduced in the 1940s, and the formula has remained almost
unchanged until the 1980s. The basic gelling agent is a small amount of cellulose acetate
and paraffin wax. The solvents were dimethylchloride and methanol. There was no
surfactant or base included, and it was washable with white spirit or IMS.
Water washable Nitromors was introduced in the 1960s. The gelling agent in this case were
paraffin wax and methyl cellulose, CELACOL MMPR1, (approximately 1.2% methyl per
glucose unit) and was produced by Courtaulds Ltd. The main solvents, as with the earlier
version, were dimethylchloride and methanol. Until the 1970s a non-ionic surfactant was
included. In the 1980s this was substituted with an anionic surfactant. In 1987 this was
replaced by a carboxylic acid amine salt (with one end neutralised and the other not). At
this date also the dimethylchloride was reduced in favor of the methanol. Borax nitrite was
also included as a corrosion inhibiter. This was recently replaced by a different corrosion
inhibiter, the nature of which is proprietary information.
Due to the very low water content of the product, the pH value is of limited significance.
However in British Standard Tests Nitromors was found to be not more basic than 5ml of
0.1m HC1 per 20g H2O, and its acidity was low enough not to react with methyl red
indicator. In their own titration tests at a concentration of 10% in water the manufacturers
gave a figure of pH 9.
(pers.comm. Mr Andrew Wood, Chemist at Henkel Home Improvements and Adhesive
Products.)
Appendix 7
Solvent Gel Tests Carried out in the
Chapel Of Our lady Undercroft, Canterbury Cathedral.
The first Carbopol solvent gel tests carried out on wall paintings by the Courtauld
Institute were undertaken in 1990 in collaboration with the Canterbury Cathedral
Wallpaintings Workshop, on the painted vault of the Chapel of Our Lady
Undercroft. The aim in this case was to produce a gel that would dissolve the thin
waxy coating applied by earlier restorers so that the more complex problem of a dirt
layer, which lay directly over the paint surface, could be removed. The gels
developed for the work at Canterbury contained relatively polar solvents and
therefore an aqueous-based gelling system could be used. Two amines were tested
to neutralise the Carbopol, Trietanolamine (TEA) and Ethomeen C/25 . The
Ethomeen C-25 (Polyoxyethylene(15)cocoamine) has cationic surfactant properties
with an HLB value of 19. Both achieved the necessary level of neutralisation (PH 7
to 7.5) at acceptable percentage volumes, however due to the possible complications
in the clearance of a surfactant from the painting surface, the TEA was used in the
final formulation. (Courtauld Institute Report, 1990).
CIA/ GCI Conservation ofWall Paintings Department. 1990-1991
An investigation into the use ofsolventgelsfor the removal ofwax-based coatings on WallPaintings.
Tobit Curteis
Sample nos.HOI - HOI 2
Accession nos. 531 - 533 & 565 - 570
County. Nor thamptonshire.
Village/Town.Holco t.
Position of painting.
North wall of the North aisle.
Name of Building.
St. Mary and All Saints
Church, Holcot.
Name/Address of Custodian.
Rev. A.J.Watkins
The Vicarage, Station road,
Brixworth, Northants.
NN6 9DF.
Permission granted. 28.1.91
Dimensions of Painting.
54 ft. long by 12 ft. high.
Subject. There are a number of subjects
depicted. Tristram identifies among others
a martyrdom of St.Thomas of Canterbury.
The test area was on the lower tier of
subjects, in the area of six standing
Apostles.
Attribution & Date.Early 14th Century.
Date. 18.2.91 Sampled by. Tobit Curteis.
Previous Recorded Surface Treatments
Date.Pre. 1950 1983
Conservator. E.W.Tristram. ? The Perry Lithgow Partnership.
Method
employed.All paintings in
the church were
coated with a
preservative treatment
of a wax based
mater iJal.
An examination was made of all the
paintings in the church but
conservation work was only carried
out on those in the south aisle (west
wall). The wax and possibly resin
coatings on this area of painting was
removed with Nitromors and methyl
chloride. Old repairs were replaced
with lime mortar fills, and the area
made sound.
Area
Treated.North aisle.
South aisle,
South aisle, west wall.
Location of
records. None.
The Perry Lithgow Partnership
samples
& location.
NoneNone.
Sheet no.2
Area Sampled (before testing)
stratieraDhv 1# Stone/rubble substrate. 2. Single layer of plaster. 3. Limewash^ p y' ground. 4. Pigment layer. 5. Waxy coating with thick deposits of
ambient dirt. In some areas there is the remains of a limewash
layer between the paint, layer and the wav.
Possibletechnique. Probably a mixture of lime and organic secco binder.
General Variable. Some areas are very sound, but there are also extensive
condition. areas of decohesion and resulting flaking in the paint layer. The
Whole painting is covered by a thick layer of surface dirt.
Appearance& yellowy translucent amorphous material homogeniously coating thedistribution
whole area of the painting. Relatively thick for such a wax layer.
ofsurfaces In many cases it fills old losses, however there are a number ofcoatings. recent losses that penetrate the wax coating.
UV Homogeneous fluorescence with a greenish tinge over the entire areaexamination. of the coating. Losses stood out clearly through their
non-fluorescence.
Positionof A11 sampies were taken in the area of the'knife'of the standingsamples. figure second from the right.
Possible anomaliesof area sampled. Sample H07 was taken through the coating in an area where
limewash remained over the red pigment layer. During sampling the
coating and limewash separated from the red original surface layer.
ftvpe & area) Tne area of tne tests wax recorded in both general and macro withKyv ' Ilford FP4 (black & white) and with Agfachrome CT100
(transparencies).
Comments.
The presence of areas of limewash between the waxy coating and the
paint surface suggests that this area was uncovered in an early
restoration of the paintings. Preliminary examination shows little
or no dirt on the original surface beneath the coating, suggesting
that it was coated soon after it was uncovered (maybe even in the
same campaign). There appear to be large area still to be uncovered
on this wall, and there also appear to be areas of palimcest.
Sheet no.
Position of Samples
Site. Holco t Chur ch Date. 18.2.91
Sample Reference
Sheet no.
Sample
number.
Accesion
number.
Type of
analysis.
Date.
HOI Sample damaged.
H02 ***
H03 ***
H04 531
H05 Sample damaged.
H06 532
H07 . 533
H08 565
HO8b 566
H09 567
FTIR
FTIR
X-Section/SEM
X-Section
X-Section
X-Section
XSection
X-Section/SEM
19.2.91
19.2.91
18.2.91
18.2.91
18.2.91
18.2.91
18.2.91
18.2.91
Sheet no.
Solvent Parameter Tests
Site. Holcot Church Date. 18.2.91
Solvent.
Xylene
Xylene
IMS
Xylene
IMS
Xylene
IMS
Acetone
Acetone
Acetone
Xylene
Acetone
Xylene 2
2
1
1
1
2
2
1 "
1
1
1
Method/Time
of application.
Swab
Swab
Swab
Swab
Swab
Swab
Swab
Result.
WS Swab
substantial amount of the coating is removed.
Cleaning action is a little quicker than above
and a greater part of the coating is removed.
Action is slower but cleaning is more
thorough than above. Curious result!
Greatly reduced and far slower cleaning
action.
No apparent effect.
Strong and relatively fast cleaning action.
more effective than the above in terms of both
speed of action and amount of material
removed from the surface. Possibly too fast
for safe cleaning.
No apparent effect.
FURTHER TEST OVERLEAF
Conclusions
The coating was clearly very soluble in a range of
solvents particularly in a mixture of aromatics. It was
surprising that it appeared to be soluble in white spirit
in its^pure form considering that the WS used in the tests
had an aromatic content of 15-25% vol/vol. Combinations of
xylene and acetone appeared to have the greatest effect on
the coating. With the exception of the WS result the test
results are consistent with the coating consisting mostly
of beeswax.
Sheet no.
Site.
Solvent.
Holcot Chur ch
Method/Time
of application.
Solvent Parameter Tests
Date. 18.2.9
Result.
1
Propan-2-ol
WS
H2O
Propan-2-ol
Propan-2-ol
Acetone
Triton X-100
Xylene 3
H2O 5
1
4
1
1
1
Swab
Swab
Swab
Swab
Swab
Slow action but the cleaning; effect appears
relatively thorough.
No effect.
Very limited effect.
Some limited effect. Better than 100% P-2-ol
Reasonable speed and depth of action.
(Clearance was carried out by swabbing with
both Xylene and H2O).
Conclusions
Sheet no
Sample Analysis Before Gel Tests
Sample no. HO 2 Accession no. ***** Date. 19.2.91
Hot Stage Examination.
Temp. Observations.
30C White/yellow amorphous translucent
material with inclusions of dirt and
white crystalline material.
65C Body of material begins to melt.
65C Majority of material melts.
67C The melted material flows free from the
white crystalline matrix (calcium
carbonate from the painting?)
>100C No further change.
Conclusions.
It appears possible that the majority of the material is wax,
possibly beeswax, contaminated with a mixture of surface dirt and
calcium carbonate from the surface of the painting.
Sample no. H03 Accession no. ***** Date. 19.2.91
Hot Stage Examination.
Temp. Observations.
30C As for H02.
64C The majority of the material begins
to melt.
66C Waxy material flows free from the white
crystalline matrix.
>100C No further change.
Conclusions.
The two samples were both taken from the edge of a loss where the
coating had gathered in a thick mass. The slight difference in
their action under TMA might be explained by the varying levels of
contamination in each sample, as well as the different thickness of
each sample.
Sheet no
Sample Analvsis Before Gel Tests
Sample no. HO 3 Accession no. Date. 19.2.91
Temp.
30C
64C
66C
>100C
Hot Stage Examination.
Observations.
As for HO2.
The majority of the material begins
to melt.
Waxy material flows free from the white
crystalline matrix.
No further change.
Conclusions.
The two samples were both taken from the edge of a loss where the
coating had gathered in a thick mass. The slight difference in
their action under TMA might be explained by the varying levels of
contamination in each sample, as well as the different thickness of
each sample.
Notable Absorbtion Peaks
F.T.I.R.
Interpretation.
Conclusions.
Sheet no
X-Section Examination Before Gel Tests
Sample no. HO 7 Accession no. 533 Date. IS.2.91
Examination Unmounted,
Surface. The surface consists of a course red pigment and is
not coated with the wax layer as this separated in the
sampling procedure.
Stratigraphy.Red pigment layer over a white crystalline ground with
inclusions of a course yellow pigment.
Examination Mounted
Normal Light (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no.100/200
Film nos.
Comments.
1. Red crystalline pigment, possibly red ochre. The
pigment layer is not bound by calcium carbonate so
there is probably a secco medium present. This is not
visible at mag. x400.
2. White crystalline matrix (calcium carbonate).
3. Small red and yellow crystalline pigment particles
Photographic records of this sample appear to have a
translucent coating on the surface. This is in fact
due to the polyester mounting resin, and not a wax
or resin coating.
Sheet no
X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HO? Accession no. 533 Date. 18.2.91
Graphic record of sample.
Photography: Film Type. ##### Mag.no. Filmnos.
Comments.
1. Very little fluorescence from this layer although thereel colour could clearly be seen under UV.
2. Bright whitish fluorescence
Staining
Type. Acid Fuchsin 2% vol/vol in H20. Rinsed with H20.
Results.
A weak stain was seen in the upper half of layer 2 of the
sample. No stain was apparent in the pigment layer probably
due to the red pigment disguising the light pink stain. The
conclusion would appear to be that there if some
proteinous material included in the limewash as and
additional binder. This may imply that the binder for the
pigment layer is also a protein.
Sheet no.
Site.
Solvent gel.
Holcot Church
Method/Time
of application.
Solvent
Date.
Gel Tests
8
Result.
.3 .9 1
1/ 7
2/ 7.
3/ 8.
4/ 2.
5/ 9.
Swab, 10/30.
Swab, 20/60.
Swab, 15/60.
Swab, 15/90.
Swab, 20/120.
Cleaning action appears to be quite
effective and fast, especially
towards the centre of the test area.
Clearance: xylene/H20. Samples: HO8a/HO8b
Action similar to test 1, but
proportionally more coating is removed,
due to the extended time period.
Fairly good level of cleaning.
Clearance: xylene/H20. Sample: HO9.
Slower action than above. Coating
appeared to be thinned but to a lesser
extent.
Clearance: xylene/H20.
Relatively good action with partial
removal of the coating.
Clearance: xylene/H20. Sample. HO10.
Slow cleaning action but a homogeneous
thinning action. Less than test 2.
Clearance: white spirit/H2O
FURTHER TESTS OVERLEAF
Conclusions
Test 2 and 6/7 appeared to give the most satisfactory
levels of cleaning with virtually all the coating being
removed. Under UV illumination this also appeared to be the
case. In niether case did there appear to be any surface
damage caused by mechanical action.
It seems likely that the clearing procedure is actually
responsible for a substantial amount of the cleaning
action.
(Samples HO11 & HO12 were taken from an area that may have
lost its surface layer due to earlier damage.)
The surface temperature of the wall at the time of the
tests was 8C. The ambient temperature was 12.5C and the
RH was 7 7%.
Sheet no.
Site.
Solvent gel.
Holcot Church
Method/Time
of application.
Solvent
Date.
Gel Tests
Result.
8 .3 .9 1
6/ 7.
7/
Swab, 10/60.
Intervention
layer.
Swab, 10/60
Intervention
layer.
The gel swells the surface coating but
does not remove it. Removal takes
place during clearance when the
vulnerable, swollen material is lifted
off by the swab.
Clearance: xylene/H2O. Sample: HO11
Similar action to the above. Overall
cleaning effect on the area after two
tests is similar to test 2.
Clearance:xylene/H2O. Sample: HO12.
(Tests 6 & 7 took place over the same area.)
Conclusions
Sheet no
X-Section Examination Before Gel Tests
Sample no. HO 4 Accession no. 531Date.
18.2.91
Examination Unmounted.
Surface.
Surface dust over a thin waxy coating.
Stratigraphy.
Surface dust, waxy costing, red pigment layer, white crystaline
substrate.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no. Film nos.
X100/X200
Comments.
1. Fine white surface 'dust' in some areas.
2. Thick yellowy translucent coating.
3. Pigment layer. Fine red crystalline particles.
4. Possibly a ground layer separate from 5. but interface isvery indistinct.
5. White crystalline matrix, dense and homogeneous.
6. Single red crystals.
7. Two large dark red/black crystals.
Sheet no
X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HO4 Accession no. 531 Date. 18.2.91
Graphic record of sample.
Photography: Film Type. Ektachrome 6 4 Mag.no. xlOO Filmnos.
Comments.
1. light white fluorescence clearly different from 2.
2. Thick layer fluorescing dark blue/ yellow.
4. & 5. Both fluoresce bright white. Distinction between the
two is made no more apparent in UV.
Type.
Results.
Sheet no
X-Section Examination Before Gel Tests
Sample no. HO6 Accession no. 5 3 2 Date. 18.2.91
Examination Unmounted.
Waxy coating with small areas of surface dust (extends around
the edge of the sample.
Stratigraphy.
Waxy coating over simple white crystalline mass.
Examination Mounted
Normal Light. (Tunosten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160. Mag.no. xlOO Film nos.
Comments.
HO6 was taken from the edge of an old (pre-wax) loss therefore
the wax has continued around the edge, and beneath the sample.
1. Yellowy translucent coating.
2. White crystalline matrix.
3. White crystalline disruption within wax.
4. Red particle.
5. Large red/black particle.
Sheet no
X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HO6 Accession no. 532 Date. 18.2.91
Graphic record of samnle.
Photography: Film Type. Ektachrome 6 4Mag.no. xlOO Fihn nos.
Comments.
1. Dark yellowy/blue layer, with littlff apparent surface dirt2. White bright flourescence..
Stainint
Type.
Results.
Sheet no
X-Section Examination After Gel Tests
Sample no. H08 Accession no. 5^5 Date. 20.3.91
Examination Unmounted.
Surface.White crystalline surface with small inclusions of dirt
particles, and possible pigment particles.
raigrapy. Apparentiy Hmewash layer over a limewash ground.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no. xl00/x200 Film nos.
Comments.
1. White crystalline layer with small inclusions of pigment
particles.
2. Second white crystalline layer, apparently slightly more
pigmented than 1.
3. Course pigment particle.
There does not appear to be any residues of the wax on the
surface of the sample and no physical or mechanical damage
is apparent.
Sheet no
X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HO 8 Accession no. 5 6 5 Date. 20.3.91
Graphic record of sample.
Photography. Film Type. Mag.no. Film nos.
Comments.
Layers 1 and 2 fluoresce with a similar bright whitish
fluorescence, but there is a clear distinction between the
two which is less apparent in visible light. There is no
evidence of any remaining wax coating on the surface of the
sample.
Staining
Type.
Results.
Sheet no
X-Section Examination After Gel Tests
Sample no.HO8ta Accession no. 5 g g Date- 20.3.91
Examination Unmounted,
Surface.
White crystalline surface with dark inclusions, probably
mixture of dirt and pigment.
Stratigraphy.
White lime layer over tinted lime background.
Examination Mounted
Normal Light (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fug i chrome 160 Mag.no. xl00/x200 Film nos.
Comments.
1. white crystalline surface layer with pigment particles
2. White crystalline layer tinted with yellow and red
(ochre?) particles.
Sheet no
X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HO8b Accession no. 5 6 6 Date. 20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
Layers 1 and 2 fluoresce in a similar bright way but the
separation between the two is apparent.
Staining
Type.
Results.
Sheet no
X-Section Examination After Gel Tests
Sample no. HO 9 Accession no. ^ 6 ? Date. 20-3.91
Examination Unmounted.
Surface.
White crystalline layer with inclusions of yellow pigment
particles. Some areas of waxy material on surface.
Stratigraphy.
Yellow tinted white crystalline layer over similar
background layer.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no. xlOO/x2OO Film nos.
Comments.
1. Fine translucent waxy layer broken in some places.
2. White crystalline layer with inclusions of yellow
(ochre?) pigment particles.
3. Dirt particles.
4. White crystalline layer with further inclusions of
yellow pigment particles.
Sheet no
X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HO9c /• n
Accession no. Date.20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Very little fluorescence from this layer, but clearly
visible against the layers below.
Layers 2 and 3 fluoresce in a similar way.
Type.
Results.
X-Section Examination After Gel Tests
Sheet no
Sample no. HO 10 Accession no. 55s Date. 20.3.91
Examination Unmounted.
Surface.
Clear waxy surface with inclusions of red particles.
Stratigraphy.
Waxy coating over a whitish crystalline layer, lower layer
has greater amount of yellow pigment particles than that
above.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
5.
Photography: Film Type Fug i c h r ome i 6 0 Mag.no. xl00/x200 Film nos.
Comments.
1. Thin waxy layer.
2. white surface layer. Very indistinct separation between
layers 2 and 3.
3. White crystalline layer with yellow and red pigment
par tides.
4. Large yellow crystalline pigment particle.
5. Small red particles.
Sheet no
X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HO 10 Accession no. 5 6 8 Date. 20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Very little fluorescence.
Similar fluorescence from 2 and 3. The interface between
the two is not clear in this sample.
Staining
Type.
Results.
Sheet no
X-Section Examination After Gel Tests
Sample no. HOI 1 • ^ fi 9Accession no. Date. 20.3.9 1
Examination Unmounted,
Surface.Surface appears waxy.
Stratigraphy.
Fine waxy coating on the surface over white crystalline
layer tinted with red and yellow pigment particles.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fug i ch r ome 1 6 0 Mag.no. xlOO/x2OO Film nos.
Comments.
1. Very fine waxy layer,
2. White crystalline layer (apparently single) with
inclusions of pigment particles.
3. Yellow and red (ochre?) particles.
Sheet no
X-Section Examination Mounted Alter Gel Tests
UV Source
Sample no. HO11 Accession no. 569 Dale- 20.3.91
Graphic record of sample.
Photography: Film Type.^4* ^a ^^ ^^ ^^ Mag.no. FUm nos.
Comments.
1. little or no visible fluorescence.
2. Apparently only a single layer. Fluorescence is quite
bright.
Type.
Results.
Staining
Sheet no
X-Section Examination After Gel Tests
Sample no. HO12 Accession no. 570 Date. 20.3.91
Examination Unmounted.
Surface.
Areas of waxy material over white crystalline surface.
Stratigraphy.
Broken waxy coating over white crystalline layer with red
and yellow particles.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Fugichrome 160 Mag.no. x200 Film nos.
Comments.
1. Broken area of fine waxy coating.
2. White crystalline matrix.
3. Small yellow crystalline particles
4. Large white particle.
Sheet no
X-Section Exaihination Mounted After Gel Tests
UV Source
Sample no. HO12 Accession no. 5 7 0 Date. 20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Little or no fluorescence.
2. Single brightly fluorescing layer.
Staining
Type.
Results.
Posilioii of Samples
Sheet no.
Site. llolco t Chui ell Dale. S - 2 . 9 1
CIA/ GCI Conservation ofWall Paintings Department. 1990-1991
An investigation into the use ofsolventgelsfor the removal ofwax-based coatings on WallPaintings.
Tobit Curteis
Sample nos.HS1 - HS8
Accession nos.528 -530, 571 - 572
County. Hampshire.
Village/Town.Winchester.
Position of painting.
South wall, West bay.
Name of Building. Dimensions of Painting.
Winchester Cathedral.
Holy Sepulchre Chapel
Subject.
Name/Address of Custodian.
John Harclachre.
Cathedral Office.
Winchester Cathedral
Resurrection of the dead
Attribution & Date.
Permission granted.
Date.
Date.
Conservator,
13.:
Pre
12.2.91
2.91
. 1900
Unknown.
Jl 1 1 L> i
Sampled by. Tobit Cur
Previous Recorded Surface Treatments
C 1900-1950
E.W.Tristram ?
c.
The
LOU
teis
1959
Eve
•
-1970
Baker Trust
Method
employed.
An unidentified material
possibly copal varnish
was applied to the
surface of the painting.
A coating of
wax preservative
was applied to
the paint surface,
over the
previous coating:.
An area of 13th century
painting on the west side
was removed to reveal the
12th century trumpeting
angel (previously
untreated). The east side
of the painting was
cleaned possibly with
Nitromors paint stripper.
Area
Treated.Eastern section
of the paintingSame area as the Tne wnoie area of theprevious treatment, painting.
Location of
records. None None The Eve Baker Trust
Previoussamples
& location.
None None None
Possible
technique.
Sheet no.2
Area Sampled (before testing)
Apparent lt stone substrate. 2. Rough plaster. 3. Possibly a fine
stratigraphy. layer of plaster in some areas only. 4. Limewash ground.
5.Underdrawing. 6. Limewash layer. 7.Paint layer.
8. Surface coatings.
Calcium Carbonate binder. (Limewash).
General
condition.Paint surface heavily abraded in many areas. Some areas of
active deterioration with severe flaking.
Appearance &
distribution
of surfaces
coatings.
Surface coatings only apparent on the eastern side of the
painting. Dark material with some form of surface residue
and considerable surface dirt.
UV
examination.
Homogeneous distribution of slightly fluorescing coating
on the eastern side of the painting. The residue on the
surface fluoresces a lighter green than the body of the coating
Positionof Central area of the painting close to the central and
samples. right hand angles descending from the cloud to rescue the
souls of the dead.
Possible anomalies In order to take samples of the most suitable areas of
of area sampled. the coating some samples were taken from areas of red
background while others were taken from areas of red.
Photography: The whole area of the painting was recorded in general and
(type&area) in macro with both Ilford FP4 (black & white) and
Agrachrome CT100 (transparencies).
Comments.
The severe abrasion of much of the painting hinders the
reading of the central section. This depicts three small
but delicately drawn angels descending from a cloud to
take up the souls of the dead that can just be discerned
at the base of the scene. This abrasion also reviles many
areas of the red underdrawing which has been exposed when
the black linear painting has been lost. Much of the
outline now visible on the large trumpeting angel on the
left of the scene is this red underdrawing. The situation
is clarified in sample HS6/530 which shows the
stratigraphy of the paint layers.
Sheet no.
Position of Samples
Site. Winchester Cathedral: HSC Date. 13.2.91
Sample Reference
Sheet no.
Sample
number.
Accesion
number.
Type of
analysis.
Date.
HS1 528
HS2 Sample damaged.
HS3 ***
HS4 ***
HS5 529
HS6 530
HS7 " 571
HS8 572
X-Section
FTIR
FTIR
X-Section/SEM
X-Section
X-Section/SEM
X-Section
15.2.91
14.2.91
14.2.91
15.2.91
15.2.91
20.3.91
20.3.91
Sheet no.
Solvent Parameter Tests
Site.Winchester: HSC
Date.13.2.91
Solvent.
Method/Time
of application. Result.
Xylene. Swab.
Xylene 2 Swab.
IMS 1
Xylene 1 Swab.
IMS 1
Xylene 1 • Swab.
IMS 2
Acetone 1
Xylene 1 Swab.
Acetone 1
Xylene 2 Swab.
Acetone 2
Propan-2-ol 1
Xylene 5
H20 5
Triton X-100
No apparent effect on the coating.
Some effect on the coating. Surface
dirt removed but majority of coating
remains in tact.
Greater cleaning effect than above
Surface dirt removed.
Similar/slightly improved cleaning
on the above, but coating still
on surface.
Slower action with less effect than
that above.
Limited slow action.
Swab. Cleaning action appears better than
(Clearance with above, but seems to rely heavily1 Swab of Xylene) on mechanical action of clearance.
FURTHER TESTS OVERLEAF
Conclusions
The use of non-polar rather than polar solvents appears to
have the greatest effect on the coating, however even when
strongly;aroinatic solvents are applied the effect is limited.
This suggests that there is a component of the coating that is
not readily soluble in standard organic solvents. The
inclusion of a surfactant appears to enhance the effect of the
solvent mixture on the coating, but even in this case it is
not readily dissolved. It is possible that there is are more
than one layer of coating on the painting, and that the
solvents are working on only a single layer leaving the others
more or less untouched. (This may become apparent with X-
section analysis or SEM). There is a substantial amount of
surface dirt that is readily removable with light mechanical
action.
Sheet no.
Site.
Solvent.
Winchester HSC
Method/Time
of application.
Solvent Parameter Tests
Date> 13.2.91 Cont. . .
Result.
Xylene 10
H2O 5
T X-100 1
Acetone
H20 5
T X-100 1
Swab. Greater effect than above, but
(Clearance with majority of coating remains
swab of Xylene) in tact.
Swab.
Swab.
No apparent effect.
Limited effect.
Conclusions
Sheet no
X-Section Examination Before Gel Tests
Sample no. HS1 Accession no. 52s Date. 15.2.91
Examination Unmounted.
Surface.Fine waxy coating and layer of surface dirt over red
pigment layer.
Stratigraphy.Waxy coating over red pigment on white crystalline layer.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Ektachrome 64 Ma*no' x2OO/x4OO FlIm nOS"
Comments.
1. Fine dark translucent layer, with areas of surface dirt.
2. Translucent, but material slightly more white and opaque
than 1. Very broken.
3. Whitish crystalline later intimately bound with 4.
4. Red pigment particles, apparently bound in the white
crystalline matrix that surrounds them.
5. Large void.
6. White crystalline material.
Sheet no
X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HS1 Accession no. 5 2 8 Date. 15.2.91
Graphic record of sample.
Photography: Film Type. ***** Mag.no. Filmnos.
Comments.
1. Yellowy fluorescence.
2. Far less fluorescence than the above. Much darker
3. Bright whitish fluorescence.
Stainlm
Type.
Results.
Sheet no
Samnle Analvsis Before Gel Tests
Sample no. HS3 Accession no. ***** Date. 14.2.91
Hot Stage Examination.
Temp. Observations.
30C Dark whitish amorphous material apparently
containing some particles of dirt.
66C Some movement of the sample observed.
68C Most of the sample melts freely.
71C Most of the sample is free flowing. There
is a small area of white apparently crystalline
residue.
>100C No further change.
Conclusions.Although the melting temperature is marginally
than would normally be expected, the majority
of the sample may still be beeswax. It could
be contaminated with certain materials (the white
residue ?) that may disperse the heat, resulting in a
higher apparent melting temperature.
Sample no. HS 4 Accession no. ***** Date. 14.2.91
Hot Stage Examination.
Temp. Observations.
30C Dark whitish amorphous material containg
particles of dirt, (similar to HS3) .
66C Some melting occurring.
67C Majority of the sample melts at this stage.
68C Majority of the sample is free flowing
leaving a residue of a white crystalline
material.
>100C No further change.
Conclusions.
Conclusions are as for HS3.
Sample Analvsis Before Gel Tests
Sheet no
Sample no. HS2 Accession no. Date. i 4 . 2 . 9 i
Temp.
Hot Stage Examination.
Observations.
30C
235C
245C
267C
272C
300C
Fine white papery material with a fiberous
celluJoser texture.
Some apparent movement in fibrous matrix.
Small voids opening in sample.
Larger voids developing and areas beginning
to darken.
Whole sample undergoes slow darkening.
Whole sample now uniformly darkened.
Conclusions.Charring appears to be occurring above 2 50C
therefore possibly some form of cellulose material
Notable Absorbtion Peaks
F.T.I.R.
Interpretation.
Conclusions.
Sheet no
X-Section Examination Before Gel Tests
Sample no. HS5 Accession no. 5 2 9 Date. 15.2.91
Examination Unmounted.
Surface. Waxy coating with surface dirt over red pigment layer.
Stratigraphy.Waxy coating with surface dirt over red pigment layer
White crystalline lower layer.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record or sample.
Photography: Film TypeEctachrome 64
Mag.no. Film nos.
X200/X400
Comments.
1. Whitish translucent coating with areas of dirt on the
surface.
2. White crystalline? deposits.
3. Large red crystalline particles. Does not appear typical
of lime/fresco technique.
4. White crystalline layer.
5. Waxy material. Whitish/brown. Maybe some contamination
after sampling.
Sheet no
X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HS5 Accession no. 5 2 9 Date. 15.2.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Yellowish fluorescence.
2. No strong fluorescence.
3. Bright white fluorescence.
4. No apparent fluorescence.
Type.
Results.
Staining
Sheet no
X-Section Examination Before Gel Tests
Sample no. HS6 Accession no. 539 Date- 15.2.91
Examination Unmounted.
Surface. ., . . n . . .Waxy coating over black pigment layer.
Stratigraphy.
Waxy coating on top of a black pigment layer intimately
bound with white crystalline matrix. Below this is a
separate white layer above a layer of red pigment. Below
this is a second white crystalline layer.
Examination Mounted
Normal Lipht. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Ectachrome 8 4 Mag.no. x200/x400
Comments.
1. Translucent whitish coating.
2. Areas of more opaque translucent material.
3. Corsly ground charcoal black pigment in white
crystalline matrix (lime).
4. White crystalline layer.
5. Red (ochre?) pigment layer. Quite pigment thin
6. White crystalline layer.
Sheet no
X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. HS6 Accession no. ^ ^ 0 Date. 15.2.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Yellowy but fairly weak fluorescence
2. Apparently no fluorescence.
3 & 4. Bright white.
Type.
Results.
Staining
Sheet no.
Site.
Solvent
Winchester
gel.
. HSC.
Method/Time
of application.
Solvent Gel Tests
Date.
Result.
1 1 .3 .9 1
1/ 7.
2/ 7.
3/ 8.
4/ 11
Swab 10/60.
Swab 10/60.
Little or no cleaning effect.
Clearance: xylene/H2O.
no further effect.
Clearance: Xylene/H20. Sample: HS7.
(Tests 1 & 2 took place over the same area.)
Swab 10/90.
Swab. 10/90
to the removal of surface dirt
5/ 1. Swab 10/90.
Apparently little or no effect.
Possible that some gel remaining on
the surface after clearance.
Clearance: xylene/H20.
No material visibly removed from
the surface, but the surface has
a shine after cleaning. Maybe due
Clearance: WS/H2O. Sample: HS8.
Again no visible cleaning effect.
Clearance: xylene/H2O.
Conclusions
There appeared to be almost no effect on the surface
coating* suggesting that it is a hard resin with no wax
component. Surface dirt is removed and a shine is left on
the surface, so it is possible that residues of some
material are being removed from the surface. (I.E. the
residues of Tristrams wax treatment that had been mostly
removed in the 1960s.)
True results will only be apparent under SEM or
visible microscopy.
The surface temperature of the wall at the time of the
tests was 15C The ambient temperature was 16c and the RH
was 6 7%.
Sheet no.
Site.
Solvent gel.
Method/Time
of application.
Solvent Gel Tests
Date.
Result.
Conclusions
Sheet no
X-Section Examination After Gel Tests
Sample no. HS7 Accession no. 571 Date. 20.3.91
Examination Unmounted.
Surface.
Fine waxy coating over reel pigment.
Stratigraphy.
Fine waxy layer over red pigment rich layer. White
crystalline lower layer.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record or sample.
Photography: Film Type Ektachrome 6 4 Mag.no. x20 0/x40 0 Film nos.
Comments.
1. Whitish translucent surface coating.
2. Red crystalline pigment rich layer with white
white crystalline binder.
3. White crystalline matrix.
Sheet no
X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HS7 Accession no. Dale. 20.3.91
Graphic record of sample.
Photography: Film Type. * He *** Mag.no. Film nos.
Comments.
1. Dark yellowy fluorescence.
2. No apparent autofluorescence.
3. Bright white.
Type.
Results.
Staining
Sheet no
X-Section Examination After Gel Tests
Sample no. HS8 Accession no. 572 Date. 20.3.9 1
Examination Unmounted.
Surface.
Waxy surface over white layer.
Stratigraphy.
Fine waxy coating over white crystalline layer with small
areas of red pigment. Second white crystalline layer below
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography; Film Type Ektachrome 64 Mag.no. xl00/x200 Film nos.
Comments.
1. Small area of red pigment particles in a white
crystalline matrix.
2. Translucent coating.
3. White crystalline layer.
4. Second distinct white crystalline layer.
5. Second area of red pigment.
Sheet no
X-Section Examination Mounted After Gel Tests
UV Source
Sample no. HS8 Accession no. 5 7 Date. 20.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Weak yellowy fluorescence.
2. and 3. fluoresce in the same bright white fashion* but
in UV there is more of deliniation between the two than in
normal light.
Staining
Type.
Results.
Position of Samples
bheet no.
Site. Winchester Cathedral: NSC Date. 13.2.9]
Solvent Parameter Tests
Sheet no.
Site. W. A. C. H. Date. 23.1.91
Solvent.
Method/Time
of application. Result.
Xylene
Propan-
Xylene
Propan-
Xylene
Propan-
Acetone
White s
White s
1
2-ol
2
2-ol
2
2-ol
pir it
p i r i t
1
2
1
•
2
Swab
Swab
Swab
Swab
Swab
Propan-2-ol 1
White spirit 1 Swab
Propan-2-ol 1
Toluene. Swab
Toluene 1 Swab
Benzyl alcohol 1
Some action apparent, possible
swelling of surface coating:, and some
material removed.
Marginally better results than above.
Action is less than the above two
tests. Apparently certain material is
removed and then action stops.
No apparent action.
No apparent action.
No apparent action.
Some slight effect. Small amount if
material is removed, including surface
dirt.
This appeared to have some effect. It
was unclear what it was removing but
there did appear to be a certain amount,
of material absorbed into the swab.
FURTHER TESTS OVERLEAF
Conclusions
The tests indicate that there area large areas where there are
two coatings present. One of these, the lower (and earlier) is
almost insoluble in solvent mixtures. This is probably the
varnish (perhaps copal) applied by Scott. Above this is a
second very broken and thin coating. This is probably the v/ax
applied by HMG. It is readily soluble in a range of aromatic
solvents. In the centre of the picture its is very thin
presumably because the majority of it was removed by EH in
1985. Towards the edge of the painting where it is obscured by
the pillars this upper waxy layer survives far thicker.
It appears that any gel would be aimed at this upper layer
only, and an alternative method should be used to tackle the
lower layer if this was considered to be desirable.
Solvent Parameter Tests
Sheet no.
Site. W.A.C.H. Date. 23. 1 .91
Solvent
Method/Time
of application. Result.
Toluene 2 Swab.
Benzyl alcohol 1
Xylene 2 Swab
Benzyl alcohol 2
Xylene 2. Swab
Benzyl alcohol 1
Acetone 1
The top (waxy) layer dissolves readily
but the problem occurs when the second
layer is reached. This appears to be
insoluble in solvent mixtures. A test
with this mixture was carried out in an
area where the waxy layer appeared
to be directly over the stone substrate
Here all the coating was readily
removed.
Very similar in effect to the above
test.
Again very similar to the above two
tests.
Conclusions
Sheet no
Sample Analvsis Before Gel Tests
Sample noWA 1 WAI Accession no. * * ** Date. 3 0.1.91
Temp.
30C
192C
2 4 8C
300C
Hot Stage Examination.
Observations.
Dark brown/yellow resinous material, quite
hard and brittle, with inclusions of surface
dirt.
Slight darkening observed.
Darkening observed throughout.
Further darkening occurs. Sample now dark
brown and opaque.
Conclusions.
Sample possibly consists of a hard resin
such as copal.
Sample no. WA2 Accession no. * *** Date. 3 0.1.91
Temp.
30C
58C
62C
64C
68C
>100C
Hot Stage Examination.
Observations.
Translucent amorphous whitish material, with
inclusions of surface dirt and white
crystalline material.
Some movement occurs.
Sample begins to melt.
Melting occurs throughout the sample.
Material free flowing leaving white crystalline
material unaffected.
No further change.
Conclusions.
The melting point suggests that the sample
consists mostly of a wax, probably beeswax.
The white crystalline material is probably
a contaminant from the wall. Soluble salts?.
Sheet no
Sample Analysis Before Gel Tests
Sample no. Accession no. Date.
Temp.
Hot Stage Examination.
Observations.
Conclusions.
Notable Absorbtion Peaks
F.T.I.R.
Interpretation.
Conclusions.
Sheet no
X-Section Examination Before Gel Tests
Sample no. WA4 Accession no. 501 Date. 2 8.1.91
Examination Unmounted.
Surface. Thick translucent layer covers surface of the sample. Apparentlywhite layer below.
Stratigraphy.1. Waxy layer, 2. Resinous layer, 3.Paint Layers containing blue
pigment particles. The paint layers appear to be saturated with
the waxy material.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film Type Ektachrome 6 4 Mag.no. x100/x200 Film nos-
Comments.
1. Sur face dirt.
2. Thick resinous layer, translucent yellow/brown
3. Carbon black? particles.
4. Small amounts of surface dirt at interface.
5. Translucent coating similar to 2.
6. Disrupted white material.
7. Dark particles-carbon black?
8. Opaque white layer. Broken in places.
9. Further original surface dirt.
10. Original surface?
X-Section Examination Mounted Before Gel Tests
UV Source
Sheet no
Sample no. WA4 Accession no. 501 Date. 29. 1 .91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Yellow/green fluorescence.
2. White fluorescence.
3. As above.
4. Dark purple.
5. White disrupted layer.
6. Bright white.
7. Light purple.
Type.
Results.
Sheet no
X-Section Examination Before Gel Tests
Sample no. Accession no. 5 0 Date. 2 3.1.91
Examination Unmounted.
Surface.Yellowy waxy surface coating with surface dirt
Stratigraphy.1. Waxy material, 2. resinous material. 3. complex mixture of
pigment layers, inc. blue crystalline pigs.
Examination Mounted
Normal Light (Tungsten Source)
Graphic record of sample.
Photography: Film Type „, , „ t Mag.no. . Film nos.B v 3 JV Ektachrome 64 xl00/x200
Comments,
1. Yellow brown coating.
2. Surface dirt.
3. Carbon black particles.
4. Disrupted white material.
5. Large dark amorphous lump.
6. Yellow/white crystalline material.
7. Carbon black particles.
8. Yellow crystalline material as in 6.
9. waxy material ?
10. as for 8
X-Section Examination Mounted Before Gel Tests
UV Source
Sheet no
Sample no. WA6 Accession no. Date. 29.1.91
Graphic record of sample.
Photography. Film Type. * *** Mag.no. Film nos.
Comments.
A. Fairly solid and coherent.
B. Very disrupted and broken.
1. Yellow green.
2. light purple-disrupted.
3. White particles.
4. Dull bluish area.
5. similar to 4.
6. Opaque white with orange tinge.
7. bright white.
8. Dark purple.
9. Darker purple/black.
10. Opaque white.
Type.
Results.
Staining
Sheet no
X-Section Examination Mounted Before Gel Tests
UV Source
Sample no. WA7 Accession no. ^ 0 4 Date. 29.1.9 1
Graphic record of sample.
Photography: Film Type. * * ** Mag.no. Film nos.
Comments.
1. White- possibly disrupted waxy material
2. Yellow/green.
3. white particles.
4. as for 3
5. opaque white layer.
6. Less opaque white.
7. light purple.
S. Opaque white with orange tinge.
9. as above, but orange more intense.
10. disrupted white.
Type.
Results.
Staining
Sheet no
X-Section Examination Before Gel Tests
Sample no. WA7Accession no.
504Date.
29. 1 .91
Examination Unmounted.
Surface.Thick resinous surface coating.
Stratigraphy.
Sample very thin. 1. waxy/resinous coating over 2. white layer
containing light blue crystals.
Examination Mounted
Normal LichL (Tungsten Source)
Granhic record of sample.
Photography: Film Type Ektachrome 6 4 Mag.no. xl00/x200 Filmnos-
Comments.
1. Sur face dirt.
2. Yellow/brown translucent coating.
3. Carbon black particles?
4. Disrupted white crystalline material.
5. Original surface ??
6. Surface dirt from above.
7. Opaque crystalline material broken in places.
Sheet no.
Solvent Gel Tests
Site. W.A.C.H. Date. 13.3.91
Solvent gel.
Method/Time
of application. Result.
1/ 7. Swab. 15/90.
2/ 1.
3/ 1.
Swab. 15/90.
Swab. 15/90.
Little apparent cleaning- effect.
Surface dirt and small amount of
coating: removed. Some small bloom
on edge of test. area.
Clearance: xylene/H2O. Samples. WA8/WA9
Again little cleaning effect. Also
some bloom at edges.
Clearance: xylene/H2O.
9FOC
Very similar to the above. Some of the
bloom removed.
Clearance: xylene/H2O.
(Tests 2 & 3 took place over the same area.)
Swab. 120. Does not appear to have any effect on
lower layer.
clearance: H2O.
(Test 9FOC took place over the area of 3. )
4/ 7.
5/ 7.
Swab. 0/120.
Swab. 15/120
Wax layer directly over stone. Shows
good thorough cleaning effect all the
way to the stone substrate.
Clearance: xylene/H2O.
Good cleaning effect, all the wax
appears to be removed. No bloom.
Clearance: xylene/H2O. Sample: WAI 3.
Conclusions
It seems clear that even gelled solvents have little or no effect
on the lower resionous layer (as was presumed from the solvent
parameter tests.) Gel 7. is the most effective for dissolving the
upper wax coating, and as there is in effect a barrier layer
between the wax layer and the paint surface, there is no danger
to the vulnerable organic components of the painting itself. Care
must be taken to avoid areas of bloom that sometimes occur.
Further examination must be carried out to establish exactly the
source of this bloom.
Position of Samples
Sheet no.
Site. W . A . G . DaLe. 30.1.91
; v
5
Sample Reference
Sheet no.
Sample
number.
Acccsion
number.
Type of
analysis.
Date.
WAI
WA2
WA3
WA4
WA5
WAG
WA7
WAS
WA9
WA10
WAI 1
WAI 2
WA13
WA14
-f* <t- T^ Jf*
50
50
50
1
2
3
#*##
56
56
56
56
0
1
2
3
564
FT I R a 0 . 1 . 9 1
FT1R 30.1.91
FTIR 30.1-91
X-Section 28. 1 .91
X-Section 28.1.91
X-Section 28.1.91
X-Section/SEM 28.1.91
SEM 2 9.1.91
SEM 29.1 .91
X-Section 13.3.91
X-Section 13.3.91
X-Sect ion 13.3.91
X-Section 13.3.91
X-Section/SEM 13.3.91
Sheet no.
Solvent Gel Tests
Site. W. A. C . H . Date. 13.3.91
Method/Time
Solvent. of application. Result.
A9C Swab. 120. Appears to have some cleaning action
on the lower coating, some material
dissolved. After clearance a bluish
fluorescence could be seen under UV on
the area of the test. Some bloom around
the edges (removed with mixture of 1/1
acetone/propan-2-ol).
Clearance: H20. Sample: WAI 4.
6/ 11. . Swab. 15/120. Test 5 was carried out twice over the
same area. On both occasions there
was a negligible result.
Clearance: WS/H2O.
Conclusions
Sheet no
X-Section Examination After Gel Tests
Sample no. WAI 1 Accession no. Date- 13.3.91
Examination Unmounted.
Surface.
Thick dark resinous layer.
Stratigraphy.
Thick coating with inclusions of disrupted white material over a
white crystalline layer.
Examination Mounted
Normal Light. (Tungsten Source)
Graphic record of sample.
Photography: Film TypeEktachrome 6 4
Mag.no.xl00/x200
Film nos.
Comments.
1. Dark translucent resinous layer.2. Dirt and white disrupted material.
3. dense white crystalline layer.
4. Small red crystals.
5. Further disrupted white effluorescence.
Sheet no
X-Section Examination Mounted Alter Gel Tests
UV Source
Sample no. WA1 1 Accession no. ^ 6 * Date. 13.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.5|C 5C fC 3C
Comments.
1. Yellow/green fluorescence.
2. Dull white.
3. Bright white.
Staining
Type.
Results.
Sheet no
X-Section Examination After Gel Tests
Sample no. WAI Accession no. 5 6 2 Date. 13.3.91
Examination Unmounted.
Surface.
Thick dark resinous coating'.
Stratigraphy.The coating lies directly over a red pigment layer on a white
ground.
Examination Mounted
Normal Light (Tungsten Source)
Graphic record of sample.
Photography: Film Type Ektachrome 64 Mag.no. xlOO/x2O(Film nos.
Comments.
1. Light red/white layer.
2. Red orange dense pigment layer.
3. Dark blackish material.
4. and 5. White crystalline material
Sheet no
X-Section Examination Mounted After Gel Tests
UV Source
Sample no. WA12 Accession no. 5 6 Date. 13.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Bright white with redish tinge.
2. Orange/red fluorescence-weak.
3. White matrix with orange tinge.
4. Similar to 3. but weaker orange.
Type.
Results.
Sheet no
X-Section Examination After Gel Tests
Sample no. WA13 Accession no. 563 Date. 13.3.91
Examination Unmounted.
Surface.
Thick dark resinous layer on surface.
Stratigraphy.
The coating lies over complex pigment and ground layers. Waxy
material is on the bottom of the sample.
Examination Mounted
Normai Light. (Tungsten Source)
Graphic record of sample.
Photography: FilmType Ektachrome 64 Mag'no' xl 00/x20rjilmnos'
Comments.
1. Translucent dark resinous material.
2. White crystalline material.
3. Dense white crystalline mass.
4. Red pigment layer in white matrix.
5. Waxy material containing large amount of dark material
(probably dirt and carbon black).
6. Blue crystals.
7 . Red Crystals.
9. Dense white layer.
Sheet no
X-Section Exaihination Mounted After Gel Tests
UV Source
Sample no. WAI 3 Accession no. 553 Date- 13.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.
Comments.
1. Reel/orange weak fluorescence.
2. Orangey fluorescence.
3. Darker than 2, but similar hue.
4. Bright white.
Type.
Results.
Stainint
Sheet no
X-Section Examination After Gel Tests
Sample no. WA14 Accession no. 564 Date. 13.3.91
Examination Unmounted.
Surface.Red broken pigment layer.
Stratigraphy.
Red crystalline pigment layer over white ground.
Examination Mounted
Normal Light (Tungsten Source)
Graphic record of sample.
Photography: Film Type Mag.no. Film nos.Ektachrome 64 xlOO/x2OO
Comments.
1. Red pigment layer. Crystalline. Uneven and broken in some
areas.
2. White crystalline material-loose matrix.
3. Large red particle of pigment ?
4. Blue amorphous crystalline particle.
Sheet no
X-Section Examination Mounted After Gel Tests
UV Source
Sample no. WA14 Accession no. 5 g 4 Date. 13.3.91
Graphic record of sample.
Photography: Film Type. Mag.no. Film nos.2|C 3|C 3{C j(C
Comments.
1. Pigment layer does not appear to fluoresce, however there
appears to be a light white fluorescence above it. Possibly
something to do with the mounting medium as there is no layer
visible.
2. Bright white with orange tinge.
Staining
Type.
Results.
CIA/ GCI Conservation ofWall Paintings Department. 1990-1991
An investigation into the use ofsolvent gelsfor the removal ofwax-based coatings on WallPaintings.
Tobit Curteis
Samplenos. WAI-WAI 4
County. London
Village/Town.
London
Name of Building.
Westminster Abbey
Chapter House.
Name/Address of Custodian.
English Heritage.
(Mr Jan Keevil)
Permission granted. 2 1.1.91
Date. 2 3.1.91
Accession nos. 501-504 560-564
Position of painting.
South arcade,
central bay.
Dimensions of Painting.
14 3cm. x 2 28cm.
Subject.
Apocalypse of St. John.
Attribution & Date.Between 13 72 and 1404.
Sampledby. Tobit Curteis.
Previous Recorded Surface Treatments
Date. 1806/36 1901/3 1929 1985
Conservator. G.G.Scott A.H.Church H.M.G. English Heritage.
Method
employed.
No exact account
survives, but it
appears that the
paintings were
Varnished during
this period.
Baryta water was
possibly applied
to certain areas
of the paintings
including the area
examined for this
project. No record
of any surface
coating applied at
this time.
Beeswax with
2% linseed oil
was applied to
the paintings &,
driven in with
heat. Used as
adhesive and
Consolident.
IMS 80 %/Propan-2-
ol 80% mixture was
used to surface
clean the
paintings in the
NW arcade. All
other paintings
were surface
cleaned with hot
air and cotton
wool to remove
part of the wax
coating.
Area
TreatedAH Paintings ?Unknown All paintings All paintings.
Location of
records.CIA/EH
CIA/EH EH EH.
Previous
samples
& location.
NoneBritish
Museum. NoneNone
Sheet no.2
Area Sampled (before testing)
Apparent i. stone substrate. 2. White ground 3. In many areas there
stratigraphy. also appears to be a red ground. 4. Paint layers (very
complex and confused in some areas.) 5. Dark resinous
layer. 6. Soft waxy layer.
Possible
technique.Organic medium of some sort (Oil?).
General
condition.Bad exfoliation and decohesion in many areas. Stone
support is often in v.bad condition resulting in surface
damage. Some areas appear to be sound.
Appearance & Organic coatings cover the whole painting. Apparently twodistribution iayers. Possibly thinned in the 1985 conservation by EH.or sorisccs
. Much of the paint surface is consolidated by the surface
coaings. coating as it appears to have lost original cohesion.Coating has collected in all damages or lacunae.
White/green fluorescence over most of coating. Some
repaints appear to show in areas of the hands and face of
figures. Two coatings not apparent in UV.
examination.
Position of
samples.All cross sections were taken from the area of the two
vscrolls' in the hand of the right hand angel. Two coating
samples taken from large lacunae nearby.
Possible anomalies
of area sampled.The very disrupted nature of the surface/coatings and
the varying staratigraphy of the paint layers may make
comparison of individual samples difficult. In most
cases the surface coatings in which we are interested
will be apparent.
Photography:
(type & area)
All areas were recorded with Ilford FP4 (black &
white) and with Agfachrome CT100, in both general
macro.
and
Comments.
Samples were intended to be as representative of the
area as possible, and comparable with other samples
from the same area. It was found that the
stratigraphy of individual samples varied considerably
within very small areas, presumably due to the damaged
nature of the paint layer. This made cross-referencing
more complex than is normal.