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METHODS AND MATERIALS USED FOR THE CONSERVATION OF MONUMENTAL WORKS IN ITALY

TIANO, P., FILARETO, C., GRANATO, A and PIACENTI ,F.

CNR -C.S. Opere d'Arte, Firenze, Italy

1. INTRODUCTION

Conservation procedures especially on monumental buildings have changed greatly in the last 20-30 years due to the use of new materials. The accelerated decay of stones exposed to atmospheric agents and therefore to pollutants has in fact created an urge to find more efficient, easy to use materials to face such an exceptional situation. Results however on aging have not often been satisfactory. The contribution of science to the understanding of the phenomena of decay, their causes, their mechanism of progress, their quantitative determination has also warned on the risks involved in the use of products whose behaviour was insufficiently known. This warning has come as the result of the scientific interpretation of the causes of the unsatisfactory results obtained from some conservation treatments made with new materials. Most of the new materials used in conservation in the last decades have, in fact, originally been created for other purposes and were used in this new field without sufficient testing. Laboratory tests are now made through the use of appropriate procedures and a convenient set of information is today available for a number of chemicals. The behaviour of products through aging is however the key factor to select and suggest them as eligible for this use. Accelerate aging procedures however are only useful for a comparative evaluation of the behaviour of different products. We are in fact, at the moment, unable to relate the results of an accelerated aging test with that of natural aging. It is therefore of great importance to collect information on the outcome of documented conservation procedures made in the recent past as proof of the behaviour of the products applied (J.M. Vallett, 1995). Through the collection of several data from appropriate sources it may be possible to draw correct indications on the results obtained using specific classes of products, on the application procedure adopted and on the cautions necessary. The F.E.C.S. (Federation of the European Chemical Societies) in order to give a scientific chemical support to the Conservation of the Cultural Heritage has created in 1987 a Working Party on "C.C.C.H." "Chemistry for the Conservation of Cultural Heritage". The W.P. has identified, as first goal of its activity, the evaluation of the results obtained with the use of chemicals in conservation procedures. Three Working Groups: "Stones", "Paintings" and "Metals" were then created to deal with the problems connected with the conservation in the related fields. We report in this paper the statistical elaboration of the data, collected in the frame of the W.G.

"Stones", concerning the conservation procedures of a number of monuments. In fact the W.G. "Stones" has organised the collection of data on restoration interventions in different regions of Italy. Such a collection was made uniform through the use of a specific form prepared by the W.G itself. In this form were listed the information which were considered relevant and necessary to give a comprehensive picture of the conservation procedures of a monument.

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2. MATERIALS

W.G."Stones" Forms The forms used to collect the data from the archives, reported at the end of this paper, include items

such as: a) Identification and description of the monument: structure, alterations, restaurations.

b) Conservation procedures performed: extent, type, restorer, firm. c) Conservation materials used and technical information on them and on the procedures adopted.

d) Control tests performed ..

e) Source of the information and identity of the collector.

The data collected in Italy originate mainly from Soprintendenze ai Beni Monumentali e Ambientali scattered in north-central Italy. 217 forms on the whole have been collected up to now in different areas concerning about 30-40 conservation cases for each area. The monuments involved are 139.

Almost all the conservation procedures considered include preconsolidation, cleaning, sealing, consolidation and protection. 839 of these phases have been registered on the whole. The products

used in these treatments have been about a hundred and the lythotipes involved have been 153. Scientific tests to evaluate the validity of the conservative intervention made have been reported only in 46 cases.

Data base To manage the great amount of data collected through the above mentioned forms, a data bank has

been built using a commercially available data base. the "MS Access 2.0". This data base was suited to creates 4 main tables, properly linked, with the following headings: • Monuments • Restauration

• Treatments evaluation • Lithotypes

The connection among these tables is such to allow simple ask-answer queries and easy statistical elaboration of all the data. Through these tables a "Monument" form is elaborated with a layout

comparable to that of the original paper forms. Which therefore may be used as the simplest way to insert all the collected archival information into the data base.

Two more tables have been created : "Chemicals" and "Stone materials". They have been considered necessary to avoid misleading interpretation of the chemical nature of the products applied for the interventions and to provide a safe characterisation of the stone material restored. The content of these last tables creates two new basic archives : one of the more frequently used chemical products with their composition and the other of the classification of the more frequently used lithotypes in monumental buildings. The chemicals used in the conservation of the cultural heritage may be found also through the information on the MCIN material data base of the CCI (Canadian Conservation Institute) through the Canadian Heritage Information Network.

3. RESULTS AND DISCUSSION

Information concerning the operations involved in restoration interventions, considered in the different geographic areas, are reported in Table 1. Cleaning is the most frequent operation (95.4%) followed

by sealing (82%). Consolidation and Protection have very similar frequency (78.3 and 79.7 % respectively) while pre-consolidation has the lowest one (51 .2%).

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Tab. 1 - Number and types of intervention recorded in the forms for different geographic areas.

Geographic N° of restoration Type and number of interventions

area forms

Recorded Verified* Pre-cons. Cleaning Sealing Consolid. Protection

Aosta 17 0 14 17 15 17 16

Emilia Romagna 55 1 34 52 46 43 38

Toscana 32 32 3 32 14 19 32

Lombardia 10 0 0 8 10 8 9

Lazio 65 5 38 63 64 50 50

Veneta 38 8 22 35 29 33 28

total 217 46 111 207 178 170 173

% 21.2 51.2 95.4 82.0 78.3 79.7

* Number of restoration intervention with assessement of the results of the treatments. The same data are reported in graphic form (Fig. 1) following their geographycal distribution. In Table

2 is reported the relative frequency of the numeber of different products used in each operation. The

highest values are usually registred for the use of a unique product with the exception of the cleaning treatment where it has been frequently (36.2%) recorded the use of more than 2 products. All the operations are mainly done using only one product. Only in the case of cleaning the use of 2 or more

products is just as frequent.

Fig. 1 - Geographic distribution of the restoration interventions registered

50 l/J c: 0

:;:::; c: 40 Q)

~ Q) -c:

..... 0

30

0 z 20

AOSTA EMIL-ROM TOSCA.NA LOMBA ROLA. LAZIO VENETO

I• Total forms 0 Preconsolidation 0 Cleaning ia Sealing •Consolidation • Protection

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Tab 2 - Frequency(%) of the number of different products used for each intervention

N° of product used Type of intervention

Pre-cons. Cleaning Sealing Consol id. Protection

1 68.5 38.6 71 .3 54.1 68.8

2 27.0 25.1 20.2 35.9 26.0

more than 2 4.5 36.2 8.4 10.0 5.2

In Table 3 is reported the frequency of use of the different cleaning procedures of stone in the areas considered. The most frequent cleaning procedures involve the use of chemicals (39.1%) and is

followed by mechanical methods (25.4%).

The geographic distribution of the most frequently used chemical brands for consolidation purposes is reported in table 4 .

Tab. 3 - Geographical distribution of the different methods used for monument's cleaning

Geographic Methods of cleaning (total 571) area

Mechanic sand-blast water liq. water spray chemicals biocides

Aosta 6 3 2 0 15 12

Em.-Rom. 14 25 14 1 76 0

Toscana 14 3 12 6 33 6

Lombardia 6 7 2 1 10 3

Lazio 15 14 17 24 64 65

Veneto 21 18 7 14 25 16

total 76 70 54 46 223 102

o/o 13.2 12.2 9.5 8.1 39.1 17.9

Tab. 4 - Geographical distribution of the commercial products most frequently used for consolidating treatments.

Geographic Paraloid Paraloid Rhodorsil Wacker Akeogard Par.872/ total area 872/ 872 11309 OH co Wacker

Drifilm OH Aosta 0 3 1 8 0 0 12 Emil.-Rom. 21 2 5 1 0 0 29 Toscana 0 0 0 6 17 0 23 Lombardia 0 0 6 1 0 0 7 Lazio 0 15 0 11 0 10 36 Veneto 6 2 10 4 0 0 22 total 27 22 22 31 17 10 129 o/o class 81.8 62.9 51.2 73.8 100 100

These data clearly indicate the existance of "preferential areas" for the use of specific products.

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In Tables 5 is reported the same information on materials used for protection Also in this case we can

recognise a regional preferential use for some products.

Tab. 5 - Geographical distribution of the commercial products most frequently used

for protective treatments.

Geographic Paraloid Paraloid Wacker Fomblin Met total area B72/ Drifilm B72 290 L Akeogard BA

Akeogard CO

Aosta 0 3 7 0 10 Emilia Romagna 18 2 0 0 20

0 0 0 19 Toscana 13 43

11 Lombardia 0 0 1 0 1 Lazio 0 9 11 0 20 Veneta 4 2 10 0 16 total 22 16 29 43 110 % class 75.9 59.3 43.3 100

The control of the treatment, reported in Table 6, has been made only a few times and is scarcely

documented.

Tab 6 - "In situ" assessement of the treatment applied

Geographic area Type of control Methodology Result

Aosta n.d n.d n.d

Emilia Romagna Colour change Visual qualitative

Depth of penetration n.r numeric

Toscana Amount of water absorbed Pipetta numeric

Lombardia n.d n.d n.d

Lazio Bulk density Ultrasound numeric (n.r)

Veneta Depth of penetration Calcimetry numeric

Colour change Visual qualitative

Colour change Munsell numeric

n.r = not recorded n.d. =not determined

4. CONCLUSIONS

The set up of our data base permits to handle a very large amount of information. The program is

organised in such a manner to give rapid statistical elaboration both on specific questions or more

general queries. One of the aims of this work is the build up of a safe statistical information on the behaviour of the

chemicals used in conservation procedures. This aim is difficult to satisfay due to the absence of

significant data such as : the amount of product applied, the determination of its penetration depth

and the evaluation of its efficiency as consolidant or protective agent. The few data present on the

original papers are mainly of a qualitative type. From the examination of the data collected we can draw the following conclusions:

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- Forms, like those we have produced, should always be used (filled) when preparing the

documentation of conservation or restoration procedures in order to provide homogeneous and

essential information. - Technical forms should always accompany each chemical product for conservation, with the indication of the active principle, of the type of solvent, of the concentration of the solution, and of the

other components. - The amount of the product applied for square meter of surface should also be reported. - The results of the scientific controls of the performance of the treatment applied, in terms of

quantitative data, should also be reported. For what concern the last point we suggest the following determinations in each restoration intervention :

Cleanly evaluation - Control of the chromatic coordinates of the surface (with Chroma meter Minolta CR 200) SEM Observation of solid silicone surface replicas.

Consolidation evaluation - Control of the depth of penetration (on drill core or with ultrasonic waves). Control of the superficial cohesion (abrasimeter or sclerometer).

Protection evaluation - Control of the amount of the water absorbed (Pipetta method).

Control determinations of the behaviour of the treatment made should be performed at least every three years after its application and should include:

- colour determination; - consolidation and protective efficacy;

- control of the behaviuor of the chemicals themselves by chemical and spectroscopic analyses.

REFERENCES

F. Piacenti "A Data Bank on Conservation Procedures of Monuments trough a P.C.'s Commercial Program". In Euroenvironment II , Vienna, October 18, 20, 1995.

Vallet, J.M., Verges-Belmin, V., Romanosky, V. "efficacite des produits employes pour la conservation de la pierre en France: premiers resultats d'une enquete menee aupres des professionels de la conservation" In the Proceeding of the Int. Colloquium on "Methods of evaluating products for the conservation of porous buildings material in monuments", ICCROM Ed., Rome 19/21 June 1995, 275-282.

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FECS - W.P "Chemistry for the Conservation of the Cultural Heritage" W.G - STONE MANUFACTS

CONSERVATION DATA COLLECTION FORM

Form n° Date Compiler

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OBJECT artefact type 0 STONE MONUMENT 0 STATUA

D OTHERS ............................................................................................. .

Name of Administration and location .... ..... .. ..... .... ..... ... .. ... ... ........ .... ..... ..... ......... ...... . Date of execution . .. ..... ........ .... ... . .. .. .. ..... .. ... ........ .. .. ...... .... .. ........ .. . ...... . ... .. ....... .. .. ..

Part of the manufact considered ....... ... .. .. .... ..... .... .. .. .. ...... .... .. .. ... ..... ............ .... .. .... ... ... . Date of last intervention .... .. ....... ... .... .... ......... ......... .. .. .......... ............................. .. ... . Photographic documents: yes 0 no 0

DATA ON MACROSCOPIC ALTERATIONS

General state of conservation

Alterations: Chromatic changes yes 0 no 0 Alveolization yes 0 no 0 Concrections yes 0 no 0 Crusts yes 0 no 0 Differential decay yes 0 no 0 Superficial deposits yes 0 no 0 Disaggregation yes 0 no 0 Detachment yes 0 no 0 Efflorescences yes 0 no 0 Erosion yes 0 no 0 Others yes 0 no 0

Geogra2hical ex2osure

Direct sun irradiaton Exposure to rain Availability of climatic data

GOOD I MEDIOCRE I BAD

Esfoliation yes 0 no 0 Fractures yes 0 no D Incrustations yes 0 no 0 Stains yes 0 no 0 Patina yes 0 no 0 Biological growths yes 0 no 0 Films Pitting Pulverization Swelling Scailing

EAST I WEST

yes 0 no 0 yes 0 no 0 yes 0 no 0

yes 0 no 0 yes 0 no 0 yes 0 no 0 yes 0 no 0 yes 0 no 0

I NORTH I SOUTH I

.... ... %of the day

.... ... % of the surface

HEAVY MEDIUM SCARCE ABSENT TOTAL PARTIAL LIMITED NO

Hydrorepellent activity yes 0 no 0

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Part of the manufact considered Name ......................... ..... ... .. ........ ....... ..... ..... ................... ......... .. .. .... ... ............ . date of execution ......... ....... ..... ...... .... ..... .. .. ...... ....... ... ..... .. ...... ...... ..... ........... .. . alterations, movements ..... ..... ... ... .... ... ... .. ... ............... .. ... .. .. ... ... ......... ... ......... .. . use ..... ..... .......... ...... ...... .... ... ....... ... .. ...... ..... ...... .... ... ... ..... ... ........ .... .... ....... ...... .

Lithotype/s Name/s ..... ..... ...... ........ ...... .. ... .... ... ... ... ......... ...... ...... .. .. ... ... .... .. ........ .. ........ ...... .

Reports General yes

enclosed Technical yes

enclosed

CHRONOLOGY OF CONSERVATION PROCEDURES

Restorer

Restorer

Conservation treatment of

Conservation treatment of

Diagnostic investigations Registered Reports enclosed

TYPE OF CONSERVATION TREATMENT

Preconsolidatio n .......................... .... D Cleaning .............................. 0 Sealing .............................. D Consolidation .............................. D Protection .............................. 0 lntergration ...................................... D

For each type of treatment specify:

Procedures used

Date

Date

Date

Date

0 no 0 no ...... .

0 no 0 no .......

yes 0 no D no ...... .

··· ····· ·· ·· ··· ····· ········ ·· ··· ···· ···· ···· ·· ···· ···· ····· ·· ····· ····· ···· ··· ·· ··· ····· ··· ········ · ···· ··· ····· · ········· ··· ··

········ ·········· ··· ··· ···· ·· ···· ···· · ··· ···· ···· ···· ···· ·· ····· ···· ········ ······· ···· ····· ·· ··· ·· ··· ··· ···· ··· ··· ·· ··· ···· ··· Chemicals used and application method

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Existing reports Reports enclosed

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Technical specifications forms of the product used Technical specifications forms enclosed

Notes on others interventions (eg. structural)

Conservation treatment of

CONTROL OF THE TREATMENT

Date

Date

yes 0 no 0 no ... ... . yes 0 no 0 no .......

Experimental tests performed immediately after the treatment

Results enclosed yes 0 no 0

Experimental tests performed later Date

Results enclosed yes 0 no 0

Date

Results enclosed yes 0 no 0

Name of W.G. coordinator .............................................. .