Wet cleaning of historical textiles: surfactants and other wash bath additives

Ágnes Tímár-Balázsy

Abstract

The paper is a review of the literature relating to the use of water, surfactants and other additives for cleaning historical textiles. Ethical considerations are introduced and the common types of soil that occurs on historical textiles are characterized. The review covers publications on the advantages and disadvantages of wet cleaning and discusses the properties of water, detergents and surface active agents. The paper underlines the importance of the HLB value, critical micelle concentration, solubility of surfactants, Krafft and cloud point in conservation. Washing processes using surface active agents, the connection between the chemical structure of surfactants and detergency, the role of soil/dirt anti-redeposition agents, foam, pH, washing time and temperature in cleaning are discussed and the composition of solutions for washing historical textiles are given. The paper introduces the dependence of rinsing on the adsorption of surfactant to textiles and reviews the use of vacuum suction in wet cleaning. The efficiency of washing and the effect of washing on fibres, textiles and dyes is assessed and the review ends with references to biodegradation of surfactants and a list of selected case studies.

Introduction

Wet cleaning is a widely used conservation treatment for historical textiles. It is a cleaning method using water as a solvent alone and as a solvent and/or medium for surface active and soil anti-redeposition agents and other additives. The use of buffers and agents involving chemical reactions between the dirt and the agent (such as sequestering agents, bleaching agents and enzymes), are not included in this review.Before the 1990s many textile conservators may have agreed with Durian-Rees who said that 'dirt is not part of old age' [1]. In the last decade of the twentieth century several publications call textile conservators' attention to the danger of removing valuable curatorial information from historical textiles by wet cleaning, for example Eastop and Brooks [2, 3], Hall and Barnett [4], Dodds [5], Brooks et al. [6, 7], Johansen [8], Stauffer [9] and Windsor [10]. However, wet cleaning has many advantages and removing harmful dirt can serve conservation as discussed by Timar-Balazsy et al. [11].

Soiling on historical textiles

Dirt or soiling is an undesirable matter adhering to surfaces and influencing their appearance. According to Akar [12], carpet sweepings contain particles with a diameter from 1 to over 20 pm, consisting of inorganic materials, cellulose fibres, animal fibres, oils and resinous materials. McKinnon and McLaughlin [13] focus on soil's adherence to fibre. Clothing in contact with human skin picks up greasy human sebum containing about 31% free fatty acids, 29% triglycerides (fats and oils), 15% fatty alcohols and cholesterol, 21% hydrocarbons and 3.3% short chains fats and oils as characterized by Patterson and Grindstaff [14]. These authors also make connections between soil release, soil type and fibres, yarn and fabric geometry. According to Powe [15], the low melting point of sebum (30 °C) is due to the complex mixture of lipids quite different from body fat. The strong bonding of fat to polyester fibres has been investigated by Weber et al. [16].The damaging effect of various stains has been discussed by Timar-Balazsy and Eastop [17, pp. 157-62] who characterize soils according to their potential to cause damage to textiles. Armstrong et al. [18] deal with the problem of removing carbon black, while Carter [19] gives an overview of iron stains on textiles. Jordan [20] reports on the removal of lime plaster from medieval woollen embroidery and Hutchins [21] and Hersh et al. [22] discuss the effect of deterioration products on

fibres. The ageing process of oil stains on textiles has been described by both Andrasik [23] and Moreland [24] and it has been found that coloured organic substances, such as dyes, inks and pigments increase the light-sensitivity of fibres. Micro-organisms, such as bacteria and micro-fungi, cause biological deterioration, characterized by Caneva et al. [25] and as Ballard [26] describes, the stiffness of synthetic resins on a textile artefact may increase on ageing, thereby inducing mechanical damage in the object.Particulate dirts, such as dust, sand, earthy material and corrosion products, may be attracted by the negatively-charged surface of textiles or may bond to the textile by rather weak electrical forces, as described by Rice [27], According to Patterson and Grindstaff [14], the removal of such particulate dirt is largely size-dependent: particles of 0.2 pm or less are almost impossible to remove from textiles by-wet cleaning. Large particles (up to 5 pm) may also be difficult to remove. Timar-Balazsy and Eastop [17, p. 159] refer to deterioration products of fibres, body oils, perspiration, finishes or adhesives, water stains, dyes and stains originating from fruits and micro-fungi as molecular soiling. Soiling forming a large mass on textiles includes greasy or oily dirt, proteins or polysaccharides, synthetic adhesives and paints.Three main types of 'dirt' are distinguished by Matteini et al. [28] according to their different response to various cleaning methods. Dirt has also been characterized according to electrostatic attraction and secondary bonds (van der Waals/dispersion, dipole and hydrogen bonds) by Moncrieff and Weaver [29, pp. 16-21] and Hofenk de Graaff [30). Kissa [31, p. 384] formulates this as follows:

'The removal of a soil particle from a substrate during laundering involves breaking an adhesive bond between the particle and the fiber. The strength of this bond, and consequently the energy required to detach the particle, depends on the attractive (mainly Van der Waals) forces and the contact area between the soil particle and the fiber surface.'

Saito et al. [32] correlate the adhesion of oily dirt with washability by applying the surface energy analysis method to the detergency system. Smith and Sherman [33] give a detailed review of the effect of fibre surface characteristics and fabric construction on soil release, and distinguish between 'micro-occlusion', in which fine soil particles became entrapped in the small crevices of fibres, and 'macro-occlusion', in which soil particles became entrapped between fibres in the yarn and between yarns in the weave. They found that 'micro-occlusion' has much more influence in the case of natural fibres than for nylon, which has a smooth surface.

Advantages and disadvantages of wet cleaning

Rice [34] emphasizes that water dissolves most of the yellow and acidic deterioration products of natural fibres; it also acts as a 'plasticizer' for the polymers of fibres, thereby improving the flexibility and softness of the textile. According to Cooke [35], water eliminates creases and wrinkles (elastic-deformations) in textiles by relaxing strains in fibres, yarns and fabrics. Flury-Lemberg [36, 37] finds it very important that in a wet state reorientation of a textile's yarns and fibres is easier and so its original texture and dimensions may be 'recovered'. Rice [38] discusses possible dimensional and colour changes, as well as dye 'bleeding' problems during wet cleaning. As noted by Tímár-Balázsy and Eastop [17, p. 194], historical textiles may undergo further deterioration during wet cleaning.

Water

Moncrieff and Weaver [29, pp. 75-7] characterize the properties of water. The fractional solubility parameters (ability to form dispersion, dipole and hydrogen secondary bonds) of water is published by Torracca [39]: (dispersion forces) N (fd)=18, (dipole bonds) D (fp)=28 and (hydrogen bonds) W (fh)=54, which indicates its very high polarity. Many salts, originating from burial conditions for

example, can be dissolved in water, except ferric (Fe3+) compounds, which are non-water-soluble according to Rice [27]. Polar organic soils, such as sugars, some types of polysaccharides (e.g..gum arable) and proteins (e.g. animal glue), dissolve in water. Seth-Smith and Wedge [40] report on the removal of animal glue from tapestry fragments.The purity of water used for wet cleaning in conservation is an important factor. Rain water, coming through the atmosphere may form acids with acidic gaseous pollutants and may carry paniculate soils and bacteria. In tap water various compounds dissolved from the ground and from water pipes can be present. The presence of cations, such as calcium (Ca2+), magnesium (Mg2+), sodium (Na + ), potassium (K+), manganese (Mn2+, ferrous (Fe2+), and ferric ion (Fe3+) in a washing solution is usually undesirable. There are three main reasons for this:The cleaning power of the washing solution for soils containing the given ion will be reduced.Compounds of heavy and transition metals are catalysts for chemical reactions contributing to further deterioration of textiles.Compounds of these metals may turn into coloured compounds by photo-oxidation or form coloured compounds with other soiling on the textile.The Guild of Cleaners and Launderers [41] gives an example: the maximum concentration of iron compounds that does not cause obvious harm to textiles is two parts of iron in ten million parts of water. However, in the case of wool the tolerance is lower: anything in excess of one half part per ten million can cause yellowing and discoloration of wool textiles. The presence of metal ions with two or three positive charges prevents the removal of ionic dirt or polar organic compounds because of their attraction for the negatively or partially negatively-charged parts of dirt molecules, thus the 'washfastness of the soiling' is improved, as noted by Hofenk de Graaff [30, 42]. To avoid this phenomenon, she advises that the concentration of cations with two or three positive charges must be very low (less than 10-5 g-ion/litre) in solutions used to wash historical textiles.Anions in tap water may also originate from water soluble-compounds (salts) found in the ground, from sulphates (SO4

2-), carbonates (CO3 2-), hydrogen carbonates (HCO3- ) nitrates (NO3

-) and chlorides (Cl-).Water hardness is caused by water-soluble compounds of calcium and magnesium. 'Hard' water is the term used to describe water that does not form a lather with soap but instead forms an insoluble precipitate, called 'lime-soap'. This whitish scum is formed from calcium and magnesium ions with the anion of the soap; it deposits in the small pores on textile fibres causing an undesirable greying of the fabric. According to Walker [43], calcium ions also form salts with anionic surfactants: calcium alkyl sulphonates and sulphates have Krafft points that are generally higher at the temperature used for wet cleaning in textile conservation, hence precipitation of the surfactant onto the textile may occur (see below for a discussion of Krafft point). The calcium salt of sodium lauryl sulphate, for instance, is insoluble below 50 °C. Arai [44] studied the effect of the concentration and the kind of detergent in hard water. A linear relationship between the concentration of detergent and water hardness at maximum oil removal efficiency was found.Filtering, softening, deionization, reverse osmosis and distillation can be applied for purification of tap water. Bede [45] suggests that conductivity measurements can be used to monitor the presence of minerals in water. In theory, pure water has a resistance of 18 megohms/cm at 25 °C, and contains 0.028 ppm total dissolved solids. Pure water is considered by some conservators to be too aggressive and thus will dissolve too much soiling (e.g. fibre/finish/ degradation products) and therefore some conservators prefer a purity of 1 to 4 megohms/cm. Distilled and deionized water are aggressive solvents capable of achieving the maximum solubility of a given compound. According to Heald [46], deionized water can be damaging to historical textiles.The 'softening' of water refers to the process of exchanging the calcium and magnesium ions in 'hard' water for sodium ions. There are two common methods of water softening: ion exchange with ion-exchange resins and formation of non-soluble or soluble compounds of calcium and magnesium with a chemical additive. Sequestering agents (also referred to as chelating agents and complex-builders) form co-ordinate bonds with metal ions to give a complex. Phenix and Burnstock [47] characterized their role in conservation. According to Hofenk de Graaff [42, 48] the calcium and

magnesium ions are held strongly in the complexes and therefore they cannot replace the sodium of soap or other washing agents. Adding polyphosphates often results in an alkaline pH of the washing solution. Di-, and tetrasodium salts of ethvlene diamine tetra-acetic acid (EDTA) are effective sequestering agents. The complex formation of disodium salt of EDTA with calcium (or magnesium) results in an increase of protons (hydrogen/hydroxonium ions) in the solution due to the exchange of the hydrogen to calcium (or magnesium). As the pH of the washing solution containing this softening agent will decrease strict control of pH is required.

Detergents, detergency

Detergents added to water create washing solutions. Their role is threefold: promoting wetting of the textile; dislodging the dirt and separating it from the fibres; keeping the dirt in a dispersion and/or emulsion. The definition given by Davidson and Milwidsky [49, p. 1] for a detergent is a formulation comprising essential constituents (surface active agents) and subsidiary constituents (builders, boosters, fillers and auxiliaries). According to Neiditch [50, p. 9]:

'Detergency refers to the process of cleaning the surfaces of a solid material by means of a liquid bath involving a physico-chemical action other than simple solution. Generally it is considered to be an unusually enhanced cleaning effect of a liquid hath caused by the presence of a special agent, the detergent.'

Surface tension of water and surface active agents

Water exhibits surface tension at the liquid-air interface and interfacial tension at the liquid-liquid or liquid-solid interfaces, according to Moore [51]. This interfacial tension hinders water from penetrating and wetting textiles. In a body of water the electric forces of attraction (especially hydrogen bonding) operate in all directions and each molecule is held in equilibrium. At the surface of water however, there are no forces acting from the air side and hence the equilibrium is disturbed. The energy accumulated in the surface molecules of water is manifested as surface tension. Surface tension is recorded as Newtons per metre and the surface tension of water is very high: 72 mN/m.Surface active agents (surfactants) reduce the surface tension of water and other liquids. When added to water, surfactants will more or less cover the surface of the liquid. They are not as strongly attracted to the inner water molecules as the water molecules were previously. According to both Niven [52] and Durham [53], the surface tension of water is reduced to the range of 25-40 mN/m in the presence of a surface active agent.Surfactants are organic compounds with molecules having a hydrophobic (water repelling) non-polar tail and a hydrophilic (water attracting) polar head or tail. As theattraction forces (hydrogen bonds) between water molecules are much stronger than those between water and the hydrophobic tail of the surfactant, the water molecules tend to 'squeeze out' the hydrophobic tail of the surface active agent. A generally coherent layer of the detergent will cover the surface, so that the non-polar tails are in the air while the hydrophilic head/part of the detergent is attracted and dissolved by the water molecules. As the hydrophobic tails of the detergent molecules are pushed out, the water spreads and wets the surface of the textile.Davidson and Milwidsky [49] give an overview of surfactants, which are divided into four groups depending on the character of the hydrophilic part: anionic, non-ionic, cationic and amphoteric surfactants. Members of the first two groups provide a wide range of washing agents, while cationic (or cation active) surface active agents are applied as optical brighteners, fungicides, softening, antistatic or colour fixing agents. Amphoteric surfactants, containing both acid and basic groups in their molecules, act either as anionics or as non-ionics depending on the pH, and have not gained importance in either industry or textile conservation. Characterization of surfactants given below is based on publication by Jakobi and Ldhr [54], Linfield [55] and Schick [56].

Anionic surfactants

The hydrophilic heads of anionic surfactants ionize to a positively-charged cation, while the residue of the surface active agent becomes a negatively-charged ion (anion). Soaps are metallic salts of fatty acids with 14-18 carbon atoms in their hydrophobic tail. They ionize in water to a positive metal ion and an anion.

Marseilles soap contains a mixture of sodium and ammonium salt of stearic acid (C17H33COONa + C17H33COONH4) and was recommended for washing historical textiles in soft water by Hofenk de Graaff [57], As outlined above, natural soaps can form a scum (lime-soap) in hard water, thereby reducing or inactivating their detergency and precipitating on fabrics. Natural soaps can cause alkaline pH in washing solutions and their cleaning efficiency is not good in cold water.Early anionic surfactants had a close resemblance to soap. Alkyl sulphates, also known as fatty alcohol sulphates (FAS), originally were made from fatty alcohols. Both primary and secondary alkyl sulphates contain 11-18 carbon atoms.

Sodium and ammonium salts of alkyl sulphates have excellent water-solubility and may form water-soluble salts with the calcium or magnesium ions of hard water, thus they do not form insoluble lime-soap precipitates. Orvus WA, a surfactant produced by Proctor & Gamble and used widely in North America, is sodium dodecyl/lauryl sulphate.Alkyl ether sulphates (AES) exhibit unique characteristics, such as very low sensitivity to water hardness, high solubility and storage stability at low temperature in liquid formulations.

Sodium C12-14 n-alkyl diethylene glycol ether sulphates, for example, demonstrate increased detergencv performance (e.g. on wool) as the water hardness increases. This is a result of the positive electrolyte effects attributable to calcium/magnesium ions. Walker [43] found the best anionic detergents for cleaning historical textiles in this group have a chain length of C12-15 and 2-3 mols of EO.Alkyl (phenol-polyethene-glycol) sulphates (APPGS) have rarely been used in conservation, apart from Levapon (Bayer).

sodium (phenol-polyethene-glycol-ether) sulphate

Sodium alkyl or alkane sulphonates (SAS) may be linear or have a branched chain:

primary secondarysodium alkyl sulphonate sodium alkyl sulphonate

Straight and branched-chain alkyl aryl sulphonates (AAS) contain 10-18 carbon atoms in their alkyl chain:

branched chain alkyl aryl sulphonate

The α-olefin sulphonates (AOS) also contain hydroxy-alkane sulphonates as a result of partial reaction with water.

α -olefin sulphonates hydroxy-alkanesulphonates

According to Hofenk de Graaff [48], α -olefin sulphonates are well known to conservators for their property of being less irritating to skin and having little sensitivity to water hardness.Another important class of anionic surfactants is the a-sulpho fatty acid esters (SFAE), particularly the methyl derivatives.

Good detergencv performance is attained only with products having a rather long hydrophobic part. One of the interesting detergencv properties of a-sulpho fatty acid methylesters is their exceptional dispersion power with respect to lime soap.Fatty acid methyl taurides, such as Hostapon T (Hoechst) are known for their excellent foaming properties.

sodium oleic methyl tauride

Straight chain (linear) and branched alkylbenzene sulphonates (ABS, LAS), exist. Until the mid-1960s, this was the largest class of the synthetic surfactant and was most prominently represented by tetrapropylenebenzene-sulphonate (TPS):

LAS has very high foaming ability; however, it is sensitive to water hardness: the detergencv power of LAS diminishes as the hardness of water increases. Smith et al. [58] attribute this sensitivity to the formation of Ca(LAS)2 on addition of calcium ions to LAS. Initially the micelles can solubilize the Ca(LAS)2 but, in the presence of a higher concentration of calcium, the micelles capacity becomes exhausted.Natural anionic surfactants are not widely used in conservation cleaning. However, the search for a biodegradable surfactant to replace Synperonic N, manufactured by ICI (see below), led to an investigation of the seaweed funori, a marine algae of the Gloiopeltis genus, by Takami [59]. The main component of the mucilage extracted from the dried sheets is a partially sulphated and methylated polysaccharide, named funoran. Using a torsion balance to measure the surface tension of eleven different concentrations of funori (0.1 to 1.5% v/v) at 20 "C, she found that it decreases the surface tension of water from the 73 mN/m to 54 mN/m, which means that it has some surface activity but less than most synthetic surfactants (24-40 mN/m). Takami's initial findings indicate that a 0.1% funori anionic surfactant solution may be suitable for washing historical textiles, subject to further tests.

Non-ionic surfactants

The term 'non-ionic surfactant' chiefly refers to polyoxyethylene and polyoxypropylene derivatives, but other surfactants are also included in this category, such as anhydrohexitol derivatives, sugar esters, fatty alkanol amides and fatty amine oxides. Non-ionic surface active agents do not ionize in water. The proportion of hydrophilic parts to the hydrophohic tails is different from that of anionic surfactants: in non-ionic surfactants the polar part/tail can be as large or even larger than the non-polar tail.Embree [60] mentions the use of soap bark (soap wort, Saponana) for washing and Cains [61] records that the soapwort plant was called 'radicula' by the ancient Greeks and Romans, who used it for cleaning wool. Shashoua [62] reports on using saponin for washing silk and Czerwinske [63] carried out experiments with Saponin DAB 9 obtained from the bark of the Chilenian Quillaja tree (Quillaja saponaria Molina) and of the roots of saponin (Saponana officinalis L). This is a non-ionic substance, which decreases the surface tension of water from 73 mN/m to 20 mN/m at 20 "C in a concentration of 1.5 g/litre. Tsujii [64] classifies saponin as two types, steroid and triterpenoid, in which hydrophilic saccharides (glucose, galactose, rhamnose, xylose, pentose, etc.) are attached to hydrophobic steroids and triterpene.Most synthetic non-ionic surfactants used in conservation are of the ethylene oxide class. If the polymerization of ethylene oxide is carried out in the presence of organic compounds containing easily exchangeable hydrogen (e.g. fatty alcohol) the product will be an ethylene oxide adduct. The proportion/size of the hydrophilic and hydrophobic part can be 'tailored' to the planned role of the surfactant in washing. Wash effectiveness shows an initial increase with an increasing degree of ethoxylation, but a point is then reached after which the wash effectiveness declines markedly.

Dillan [65] found that narrow-range1 ethoxylates contain less unreacted fatty alcohol and other water insoluble species and they are capable of forming aqueous solutions with much lower cloud points than their broad-range counterparts.The general formula of alkylphenol polyglycol ethers (APEO) is as follows:

These surfactants, which have exceptional detergency properties and, in particular, oil and fat removal characteristics, show low biodegradibility (for a discussion of biodegradability, see below) Synperonic N is an ethylene oxide adduct (EO = 8) with nonylphenol.

HLB

The detergency of a surfactant depends greatly on the balance (B) of the molecular weight of the hydrophobic (H) portion to that of the hydrophilic (lipophylic, L) portion. Porter [66] asserts that calculation of the HLB number was first proposed in 1949. HLB = % of the hydrophilic group (molar) divided by 5. The maximum HLB number is 20 and represents a completely water-soluble surfactant, while an HLB of zero represents a completely water-insoluble product. Boring and Ewer [67] make a connection between HLB value and application:

Table 1 Connection between HLB values, appearance on adding surfactant to water (after Porter [66] and Boring and Ewer [67])

It should be noted that an increase in temperature will bring about a phase inversion from an oil in water (OAV) to a water in oil (W/O) emulsion due to the non-ionic surfactant becoming less water-soluble as the temperature increases. Delcroix and Bureau [68] suggest that for non-ionic surfactants, it is better to use a mixture of surfactants with different HLB values, giving the desired proportions, than to use a single one that has the required HLB value. A strongly hydrophobic surfactant has a low HLB, usually less than 10. A highly hydrophilic surfactant has a value higher than 10. For example, polyethylene nonylphenols have an HLB of about 13 and sodium lauryl sulphate has an HLB value of approximately 4.According to Kravetz via a personal communication with Walker [43], solutions of linear primary alcohol ethoxylates C12-15, EO 3 to 4 mols, blended and mixed with varying HLB values are efficient for washing historical textiles. Surfactants of HLB 10 to 12 are effective for oily soil and those with a higher HLB, 13 to 15, for particulate soil. Walker recommends a two- or three-step washing process, starting with a lower and ending with a higher HLB surfactant.

Wetting properties of surfactants

In the presence of a surface active agent, the interfacial tension between water and textile is reduced and the textile is wetted. Various surface active agents show various wetting properties, depending on their chemical and stereo-chemical structure (e.g. the length of hydrophobic and hydrophilic parts, straight or branched chains and the presence of an aromatic ring in the molecule). The wetting property of a surfactant is characterized by the measurement of the 'rim angle' and 'contact angle', described by Bigler [69].The 'rim angle' is the tangent of the angle between the solid and the liquid surface measured in the air. It increases as the wetting increases. Ward and Benerito [70] define 'contact angle' as the angle between the solid surface and the tangent of the liquid surface as it approaches the solid, the angle being measured in the liquid. The contact angle decreases as the wetting increases.

1 When reacting detergent-range primary alcohols (C12-14) with ethylene oxide and achieving a narrow distribution of EO moles.

The rolling-up process by surfactants in the case of liquid dirt, such as oil, can be characterized so that the fibre surface is wetted by the oil in the starting state and then it will be wetted by the aqueous phase. This process, which results in cleaning, can be followed by the decrease of the rim angle and an increase of the contact angle between the oil stain and fibre while it is rolled up by a surfactant solution, as depicted by Lange [71, p. 158]. At the beginning of the rolling-up process the oil is a flat stain on the surface of the textile. As it is lifted up step by step it curls in a ball-shaped oil particle and separates from the surface of the fabric.

Critical micelle concentration

The total number of surfactant molecules that enter the liquid surface is determined by a balance of forces: between those squeezing out the hydrophobic tails and the repelling forces between like-charged parts of the surfactant molecules. When a surface active agent is added to water, so that its concentration gradually increases, the number of the surfactant ions at the surface increases up to a certain critical concentration of the detergent. The excess surfactant molecules (i.e. those added since the critical concentration was reached) cannot access the surface or stay individually in solution but form micelles within the body of the liquid. Hence the term critical micelle concentration (cmc).Hutchinson and Shinoda [72, p. 13] define micelle as 'hydrated surfactant in liquid state'. Since the micelles are small compared with the wavelength of light, the solution is transparent. According to the above authors, micelles have a solubilization power: when the surfactant solution is above its cmc, the solubility of a third additive is markedly greater than in pure water. Wentz [73] also attributes the main mechanism of soil removal in aqueous systems to this solubilization, by stating that non-polar substances are solubilized in the interior of the micelles. Skagerlind [74] published an illustrative figure showing that surfactant molecules are present in single form below, and in micelle form above cmc.Micelles are aggregates of a number of surfactants. The hydrophobic tails of the surfactant molecules tend to cluster so that they are isolated from the water; in other words, the water molecules squeeze out the non-polar tails of the detergent molecules. The hydrophilic parts of the surfactant align themselves facing the water. Many suggested configurations for micelles have been suggested, such as spherical, ellipsoid, lamellar and cylindrical; the micelle configuration is thought to depend on the chemical composition and stereo-chemical structure of the surfactant.The micelles themselves are stable entities; however, they continually break up and reform in a process of equilibrium. With anionic surfactants the outer layer of the micelle is negatively-charged, with non-ionics, the micelles have no charge. According to Delcroix and Bureau [68], the number

of molecules in a micelle at room temperature is 40-499 for a non-ionic surfactant and 20-300 for an anionic one.As mentioned by Taylor [75], the cmc varies markedly according to the character of the surfactant as it is affected by temperature. At low concentrations the amount of micelle formation is negligible and, at higher concentrations, the point of equilibrium is to a very great extent independent of the total concentration. The reverse applies to surface tension: at low surfactant concentrations the reduction in surface tension is dramatic, but it does not change above the critical micelle concentration.Hofenk de Graaff [30] remarks that the effectiveness of a washing agent increases up to the critical micelle concentration but decreases after cmc has been reached. Lange [71, p. 173] distinguishes between the mechanism of single surfactant molecules and micelles in cleaning. He explains that the increase of cleaning efficiency up to the cmc is due to adsorption of the single surfactant molecules onto the dirt. Thus, solubilization of the dispersed dirt is a purely micellar phenomenon. It therefore does not occur unless the concentration is higher than the cmc. The actual mechanism depends both on the surfactant and the type of soil. It seems to be a general experience that a strong increase in cleaning efficiency occurs up to the cmc and only a very slight increase above the cmc.The critical micelle concentration of any one class of surfactant is reduced as the size of the hydrophobic tail increases, or the hydrophilic part decreases in size. The closer the polar group to the centre of the hydrophobic tail (in secondary alkyl sulphates/sulphonates), the higher the cmc. The presence of more ionic groups in one surfactant molecule also causes an increase in cmc. The cmc also depends on the cation of the surfactant. It reduces cmc with decreasing attraction forces between the detergent ion and the cation: the reduction in cmc is smaller with sodium than with potassium. According to Juhasz and Lelkesne Eros [76, pp 126-38], with non-ionic surfactants the cmc increases as the hydrophilic part (EO) becomes larger.From these observations it is clear that non-ionics produce lower surface tensions than anionics at equivalent concentrations. Also, at comparable hydrophobic chain size, non-ionics form micelles more readily; this is probably because, without an ionic charge, there is no barrier to aggregation, as noted by Taylor [75, pp. 10-11]. One of the advantages of using non-ionic surfactants is that the critical micelle concentration is very low, in the order of 0.05-0.5 g/litre in comparison to anionic ones with a cmc of 0.3-3 g/litre, thus, the amount of surfactant required is reduced, thereby increasing liquor clarity and rinsability.According to Juhasz and Lelkesne Eros [76, p. 138], in aqueous solutions the cmc of anionic surfactants is reduced in the presence of salts of the surfactant's cation. In addition, the repelling forces between the polar parts of non-ionics are reduced by certain cations. This may explain why sequestering agents providing cations on ionizing reduce the cmc of the detergent. Dirt containing a similar cation to those of the anionic surfactant may have a similar effect, that is such soiling may reduce the cmc of anionic surfactants. Thus, when wet cleaning archaeological textiles contaminated with sodium compounds, a lower concentration of an anionic washing agent may be as effective as one of its cmc.

Solubility of surfactants, Krafft point and cloud point

The solubility of surfactants depends largely on the length and proportion of their hydrophobic and hydrophilic parts (HLB), as well as the number and position of ionic or polar groups. According to Davidson and Milwidsky [49, p. 10], lauryl alcohol reacted with ten molecules of ethvlene oxide is completely water-soluble and a good detergent, while one with less that five molecules of ethylene oxide would be insoluble.Temperature is another factor that determines the solubility of surfactants. Below a certain temperature, the apparent solubility of an anionic surfactant drops dramatically. In contrast, the solubility of non-ionic surfactants drops considerably above a certain temperature. The temperature at which the solubility of a surfactant decreases sharply and the undissolved detergent molecules appear in the form of a whitish cloud, is called the 'cloud point'. In a 'cloudy' solution only the

soluble (invisible) portion of the surfactant carries out its surface activity. Zika [77, p. 27/324] gives the following definition: 'nominal cloud point: the temperature at which a cloud of insoluble surfactant first begins to form in a 1% aqueous solution of the surface active agent'.The solubility of anionic surfactants depends basically on the length of the hydrophobic chain. If there are fewer than 10 carbon atoms in the non-polar chain, the detergent may be too soluble to form micelles suitable for soil removal. If it contains more than 18 carbon atoms, the anionic surfactant molecule is too large to be soluble at reasonable working temperatures. A surfactant with unsaturated hydrophobic chains is more soluble than a similar saturated chain compound. Rice [78] gives an example: a sodium oleate surfactant (C17H33iCOONa) with an unsaturated chain dissolves in cooler water than its saturated counterpart, sodium stearate surfactant (C17H35COONa).The solubility of anionic surfactants increases as the temperature rises and hence cloudy solutions clear as their temperature is increased. There is a critical solubility temperature, called 'Krafft point': above this temperature the solubility of the anionic surfactant increases dramatically with increasing temperature. Micelles cannot form below Krafft point. Walker [43] provides an example: the Krafft point of SDS is about 10 °C. At 12 °C its solubility is 0.02%. This increases to 0.2% at 16 °C and to 3% at 17 °C.Hutchinson and Shinoda [72] formulate that at low temperatures the precipitate of anionic surfactants will be in equilibrium with the saturated solution of singly dispersed surfactant molecules. In contrast, at high temperatures the precipitate becomes transformed to a liquid state. If the temperature cannot be varied under practice conditions, another equivalent effect may be to change the molecular structure of the surfactant or to add a third component in order to depress the Krafft point. Branching or unsaturation in a hydrocarbon chain causes a marked reduction of the Krafft point.In contrast, the cloud point temperature of non-ionic surfactants can be rather low and the 'cloud' appears above the cloud point temperature. The solubility of non-ionics decreases as temperature rises. Different theories are advanced to explain this particular cloud point phenomenon, described by Zika [77] in a paper in 1969. One states that the hydrogen bonds, formed between the polyethylene oxide part of the detergent and the water molecules, break with increasing temperatures. The higher the temperature the more hydrogen bonds break. As a result, the surfactant becomes insoluble. Another theory claims that with increasing temperature the micelles of the non-ionic surfactant grow larger, to the point where they can actually be seen in the form of a 'cloud'.Water hardness greatly influences the solubility of detergents. Those anionics that form non-water-soluble compounds with calcium or magnesium (such as soap, alkyl benzene sulphonates or secondary alkyl sulphonates) have a much lower cloud point than other anionics. Non-ionics are not usually sensitive to hard water and it is the presence of electrolytes that lowers their cloud point. Jakobi and Lohr [54, p. 57] note that in the presence of pure non-ionic surfactants the cloud point can be reduced greatly by the addition of several grams of electrolytes.

Washing process with surface active agents

In general, the wash effectiveness of anionics increases with increasing chain length, as described by Jakobi and Lohr [54, p. 42]. For example, surfactants bearing n-alkyl groups show a linear relationship between the number of carbon atoms in the surfactant molecule and the logarithm of the amount of surfactant adsorbed on activated carbon or kaolin. The structure of the hydrophobic residue also has a significant effect on surfactant properties. Surfactants with little branching in their alkyl chains generally show good wash effectiveness but relatively poor wetting characteristics, whereas more highly branched surfactants are good wetting agents but have unsatisfactory detergency. For compounds containing an equal number of carbon atoms in their hydrophobic residues, wetting power increases markedly as the hydrophilic groups move to the centre of the chain or as branching increases, but a simultaneous decrease in adsorption and washing power occurs.

The micelles formed around the cmc provide reserves of surfactant molecules, which are not only available for instant mobilization, but also have the power to solubilize substances, such as fat, which do not dissolve in water. Taylor [75, p. 7] describes fat as being 'solubilized' within the hydrophobic interior of the micelle.In wet cleaning textiles, a surfactant solution is applied and soil removal is promoted by careful agitation. According to Kissa [79, p. 763]:

'The process of washing (soil release) consists of three consecutive stages: an induction stage, during which water diffuses into the soiled textile but soil release is slow; a rapid soil release stage, during which 'rolling up' and dislodgement of soil and water diffusion are rapid; and a final stage, during which soil retention in the textile remains essentially constant'.

The hydrophobic tail of a surfactant penetrates hydrophobic soiling, while the polar part of a non-ionic penetrates polar soiling. Through the penetration of surfactant molecules, the soiling on a textile surface is dislodged (deflocculated) into small particles. The four stages of this process are depicted in an illustration in a paper by Moncrieff et al. [29, p. 84].Anionic detergents require a long time to penetrate negatively-charged soils, such as clay or carbon black, due to the mutually repelling forces present. Diffusion of the surfactant into the textile is hindered by the repelling action between the anionic surfactant and textile, which also has partial negative charges on its surface due to the polar groups of the fibre polymers. Anionic detergents dissolve soiling particles of non-polar character in the micelles and they bond to polar soils by secondary dipole and hydrogen bonds with their polar heads. In the case of polar soils, a second layer of surfactant molecules joins the first layer and thereby a double anionic surfactant layer prevents polar soiling particles from aggregation.According to Zika [77], non-ionic surfactants are equally good at penetrating both non-polar and polar soils due to the equal length of non-polar and polar parts and the absence of any charge. Non-ionic surfactants bond to polar soils by dipole and hydrogen secondary bonds with their polar parts and by van der Waals bonds to non-polar soiling with their non-polar parts.Non-ionics penetrate soiling and textile quite quickly, especially if the hydrophobic part is of a straight chain type. Non-ionic detergents with 12-14 carbon atoms in their alkyl chain and 10 EO groups are excellent at penetration, but octyl- to dodecylphenol detergents with 10 EO groups are also very effective at soil penetration.Applying a mixture of anionic and non-ionic surfactants in the same washing solution has the advantage of forcing off soiling by the anionic surfactant and at the same time penetrating various soiling by the non-ionic surfactant. Berol 784 (Berol Nobel), for example, is a mixture of an anionic (alkyl aryl sulphonate) with a non-ionic (fatty alcohol ethoxylate) surfactant. Gentle and Muller [80] combined anionic and non-ionic surfactants in the same washing solution and achieved a good result in terms of cleanness. Lewis [81 ] experimented by mixing Synperonic A5 non-ionic and SDS anionic surfactants and found its efficiency better than either single surfactant for washing wool. Stauffer [82] provided the author with leaflets on two mixed surfactants used by German textile conservators: Invadin LUN (Ciba-Geigy) and Kieralon OLB (BASF).

Chemical structure of surfactants and detergency

Stupel [83J lists surfactants according to their increasing cleaning power: primary fatty alcohol sulphate —>alkyl polyglycol ether —>alkyl aryl sulphonate (dodecilbenzene sulphonate) —>secondary fatty alcohol sulphate (tridecylsulphate) —>fatty acid condensation product (oleyl methyl taurine) —>alkyl sulphonate.Jones [84] reported on variables affecting efficiency of amonic surfactants in soil removal: straight alkyl chains on benzene sulphonates are superior to branched chains; effective detergency of benzene sulphonates begins with an alkyl chain length of 10 carbon atoms and improves to a

maximum at 14-16 atoms; p-alkylbenzene sulphonates are superior to o-alkyl compounds; straight-chain carboxylates and sulphonates have similar detergent activity.Harris [85] and Schonfeldt [86] investigated surfactant effects and summarized that optimum soil removal activity for non-ionic surfactants is produced by condensing ethylene oxide with a normal straight chain aliphatic hydroxy compound with 12-14 carbon atoms in the chain and about 10 ethylene oxide units. They found that branched alkyl chains give less efficient detergent action than straight chains and that aromatic derivatives, such as octyl- and dodecylphenol, provide effective non-ionic surfactants when condensed with about 10 mols of ethylene oxide. Non-ionicsurfactants soluble in dilute solution at room temperature can become insoluble at higher temperatures and their detergent action is optimized close to this condition, while low levels of non-ionic surfactants form micelles in water so that the amount of these compounds needed for optimum soil removal is less than that of anionic surfactants. The authors noted that effective soil solubilization shown by non-ionic surfactants is an additional removal mechanism not available with ionic materials and that non-ionic and anionic surfactants combined in detergent mixtures can give more effective soil removal than either surfactant alone.When evaluating surfactant groups according to their cleaning power one has to bear in mind that the actual effect of the surfactant chosen depends on the individual surfactant selected from a particular group, the type of textile and soiling and other components of the washmg solution as well as the washing temperature, pH, mechanical action and the duration of washing.Soil/dirt redeposition and soil/dirt anti-redeposition agentsIn the last stage of washing the role of the surfactant is to keep the dislodged soil particles in a stable suspension, dispersion or emulsion and prevent soil redeposition on the textile. According to Rice [27], an average strongly-adhered, plate-like clay soil particle is about 0.1 µm in diameter. Carbon deposits that exhibit strong greying power appear to be about 0.05 µm in diameter. Having been broken down by the surfactant, the soils turn into much smaller particles, which can deposit in the surface crevices of vegetable fibres, at the junctures of animal fibres with scales and in the complex surface structure of some synthetics. Such fine, redeposited soiling results in a dull, uniformly grey appearance, which is very difficult to remove. Rice [27, p. 13] discusses the problem in detail.Hofenk de Graaff [30] characterizes washing as a process of equilibrium where the amount of soil 'rolled up' by the detergent is in equilibrium with the amount of redeposited soil:

The equilibrium is shifted in the direction of the upper arrow if dirt is held strongly in the washing solution. Redeposition of soiling can be prevented if a washing solution loaded with dirt is replaced before the equilibrium is shifted towards the lower arrow.Hence, like-charged 'soil-surfactant micelles' repel each other and are repelled by the textile, anionics usually act well in preventing soil-redeposition. The dirt-carrying properties of anionic surfactants are usually excellent if the surfactant is present above its cmc. Non-ionics solubilize or retain mixed non-polar and polar soils (i.e. greasy dirt) in a stable dispersion, whether or not they are present below or above their cmc.Juhász and Lelkesne Eros [76, p. 239] state that the use of a mixture of anionic and non-ionic detergents in the same washing solution has advantages for soil-carrying. For example, the anionic detergent sulpho-succinate does not have very good washing properties but is excellent in soil-carrying; this applies also to anionic fatty acid-alkanol-amides, which also promote the stability of foams.

Patterson and Gnndstaff [14] list special soil anti-redeposition agents, such as polyvinyl alcohol, polyethylene-glycol, polyvinyl pyrrohdone as well as sodium carboxy methylcellulose hydrophilic polymers. The most common soil carrier used in washing historical textiles is the carboxy methylcellulose (CMC) and its sodium salt (SCMC or NaCMC). A paper by Lange [71, p. 155] refers to several theories about the mechanism of inhibiting soil redeposition by CMC and SCMC, such as reinforced electrical repulsion, competitive adsorption, protective colloid action and steric protection.The usual recommended concentration of SCMC in a washing solution is 0.01% of the quantity of the surfactant. Complete dissolution of SCMC requires a rather long time (about 24 hours). Smith and Lamb [87] recommend SCMC with a small degree of polymerization (DP = 200-500) and with a low degree of substitution (DS = 0.6-0.8) for soil-carrying purposes. ]akobi and Lohr [54, p. 90] mention the use of carboxymethyl starch (CMS), as well as non-ionic cellulose ethers. The cellulose-based soil anti-redeposition agents are particularly effective with cellulose-containing fibres. These agents form a barrier layer on the surfaces of cellulosic fibres. The advantage in soil-carrying is a disadvantage in separating cellulose-based soil anti-redeposition agents from cellulosic textiles, which require repeated rinsing at rather high temperatures.Sequestering agents also act as soil carriers, partly by forming complexes with the metal ions of dirts, partly by their dispersing, emulsifying and stabilizing properties, which are limited in comparison to surfactants.

Composition of washing solutions for historical textiles and methods of washing

Commercial washing powders and liquids are unsuitable for cleaning historical textiles due to the presence of many unwanted additives, such as complex builders, optical brighteners, enzymes, corrosion and foam inhibitors, bleaching agents, stabilizing agents, dyestuffs, fillers and perfumes. These are described in papers by Lehmann [88] and Hofenk de Graaff [57].In an unpublished report Wyeth [89] lists specific surfactant properties desirable for a conservation cleaning agent: effective lowering of interfacial tension; good wetting power; low cmc; high solubility at low temperatures (i.e. low Krafft/cloud point); efficiency at neutral pH range; low sensitivity to water hardness; good detergency; soil anti-redeposition capabilities; rinsability; neutral odour; favourable handling characteristics; acceptable biodegradability; storage stability; reasonable price and availability in small quantities.Hofenk de Graaff [48] recommends various formulations for washing historical textiles taking into account the fibres of the textile, nature of the dirt, quality of the water and the foaming property of the detergent. Collins [90] advocates non-ionics and natural soap for washing undyed cotton and linen. Shashoua [62] describes a so-called 'Standard Washing Solution' used for experimental cleaning purposes. Boring and Ewer [67] surveyed wet cleaning and found that anionic surfactants were used in a concentration of 0.2-0.5% and non-ionics in a concentration of 0.05-0.02% at 20-27 °C. For washing, the use of deionized water and for rinsing the use of tap water was reported. Hogberg [91] reports an opposite approach, using tap water for washing and deionized water for rinsing.Washing solutions for historical textiles normally contain a surfactant, either an anionic surfactant in a concentration of 0.5 to 1.0 g/litre, or 0.1-0.5 g/litre of a non-ionic surfactant as well as distilled, deionized, demineralized or soft water. General formulations for detergents are summarized by Daniels and Shashoua [92). The Canadian Conservation Institute have produced two notes [93] and a report [94] on the wet cleaning of textiles, recommending a 0.5% concentration of anionic detergent for cleaning textiles in cultural heritage collections.In general, non-ionic and anionic surfactants combined in a single detergent mixture result in more effective soil removal than any single surfactant alone, especially in the conditions appropriate for treating historical textiles, according to Patterson and Gnndstaff [14]. What is probably the first published report on using both kind of detergents for cleaning a piece of historical textile dates from 1966, when Rice [95] used a fatty alcohol sulphonate anionic detergent in the first wash bath and an

ethylene oxide condensate non-ionic in the second. Cox et al. [96] investigated the interaction between LAS and non-ionic surfactants and found that the addition of low levels of a lauryl range-high EO non-ionic surfactant significantly lowers cmc and causes the formation of micelles containing predominantly non-ionic molecules. Non-ionic surfactant enhances LAS hard water performance by preventing the loss of LAS via Ca(LAS)2 precipitation. The non-ionic surfactant acts as a micelle promotion agent, while LAS remains responsible for surface and mterfacial properties. Davis [97, pp. 159-63] reports on using a 2 g/litre solution of Synperonic N non-ionic surfactant mixed with a solution of 0.5 g/litre sodium dodecyl sulphate, anionic surfactant. For washing a severely soiled curtain she used a solution of 0.5 g/litre Synperonic N, 0.5 g/litre sodium dodecyl sulphate and 2.00 g/litre SCMC.Hofenk de Graaff [98] lists the following additives as sometimes also being used in washing solutions; a soil-carrier of sodium carboxy methyl cellulose (SCMC) in a usual concentration of 0.05-0.1 g/litre; a sequestering agent, which can be added to soften water and/or to remove heavy soils containing metals, in a usual concentration of 0.5 to 2.0 g/litre and a buffer, added to maintain the pH of the washing solution when treating highly acidic textiles.In washing solutions for historical textiles the use of distilled, demineralized, deionized or soft water is recommended. Giuntini and Bede [99] used deionized water without any detergent for washing a group of Paracas mantles, as did Kajitani [100] when wet cleaning a Munghal court robe. Distilled water alone was recommended for wet cleaning of archaeological textiles by Zongyou [1011. A 0.2% solution of Synperonic N non-ionic surfactant containing 0.005% CMC was used by Kiefer [102] for cleaning a shattered silk brocade.Cussel [103] compared the British and the French methods of wet cleaning and noted that there is little difference between them, although in the UK Synperonic (ICI), and in France Tinovetine (Ciba-Geigy), are the preferred surfactants. A detergent formula containing Synperonic N non-ionic surfactant, SCMS and sodium tripolyphosphate was published by Glover [104] in a report on the textile conservation methods in north-western England.Burgess [105] suggests that textiles made of cellulosic fibres should be washed and rinsed in a solution containing 20 to 200 ppm of magnesium sulphate (MgSO4) dissolved in distilled water. This reduces the loss of calcium and magnesium from the cellulose (hemicellulose and pectin) and thereby improves the stability of the polymers of the vegetable fibres. In a personal communication, Hofenk de Graaff [106] felt that this method should be subject to further debate, as the presence of calcium and magnesium ions in the wash bath hinders soil removal and, unlike paper, the quantity of calcium and magnesium in cellulosic fibres is very low. Shenai [107] recommends using non-ionic, rather than anionic, surfactants to wash wool because they have a lack of substantivity to wool. Delcroix [108] gives a sophisticated mathematical process for determining the ideal concentration of a surfactant used for wet cleaning historical textiles for the Mai son Chevalier in Aubusson, France.

Washing temperature

The washing temperature has a great influence on the solubility (i.e. cloud point) of surfactants. The solubility of anionics increases as the temperature rises. Surfactants, with long polar chains, for example non-ionics, dissolve readily in cold water. The solubility of non-ionics decreases as the temperature rises. Alkyl sulphate anionics with 14-16 carbon atoms in their chain are excellent washing agents with good micelle formation and soil dispersing properties. Their use requires the temperature of the washing solution to be above 40 "C to reach the critical micelle concentration. This temperature is too high for textile conservation purposes because of the damaging effect of swelling, shrinking, felting or hydrolysis of degraded fibres, as well as bleeding of dyes or dissolution of too many degradation products. Thus, anionic detergents are often used in conservation at lower temperatures, i.e. below their cmc.According to Morris and Prato [109], the effect of the washing temperature on the removal of particulate and oily soiling depends on the fibre type too. Generally from both cotton and polyester

fabric the dirt removal improves as washing temperatures increase from 10 to 54 °C. Removal of non-polar oily soil from polyester fabric was a notable exception, where soil removal was inversely related to wash temperature. Myers [110] distinguishes between wet cleaning and laundering, stating that the latter term refers to cleaning at high temperatures.

Washing time

To prevent too much swelling or hydrolysis of degraded fibres, the duration of washing of historical textiles is normally reduced as much as possible. The use of a suction table in wet cleaning can reduce the time available for fibre swelling. On the other hand, according to the three consecutive stages of washing (induction time, rapid soil release stage and final stage), it is not advisable to stop washing before the rapid soil release stage is reached.The induction time of washing is usually shorter with non-ionic surfactants than with anionics due to the lack of repelling ionic forces between the textile, soil and surfactant. Naturally, the induction time depends on the fibres, the thickness and structure of the textile, the hydrophobic property of the soils, the temperature of the washing process and the components of the washing solution. Complete wetting can be achieved in minutes or may take hours, depending on the above factors. In wet cleaning of historical textiles the rapid soil removal period should start and reach equilibrium within a reasonable time. The washing process for historical textiles should stop before the end of the rapid soil release stage in order to prevent soil redeposition, as mentioned above with the 'equilibrium process theory' of washing. If a single washing solution is insufficient to achieve the required soil removal, the use of two, or more, washing solutions is recommended instead of soaking the textile longer in the same bath. With a second or subsequent bath the rapid soil release stage starts again, and the risk of dirt redeposition is therefore reduced.When analysing the answers to the questionnaire 'Operation Wetclean', Howell and Farnsworth [111, p. 55] concluded that 'rinsing times are longer than wash times, wool tends to be soaked before washing but silk does not, the longest treatment time tends to fit into a working day, although some conservators were doing very long days.'

The pH of the washing solution

Anionic surfactants require complete ionization for optimum washing efficiency. Anionics in the form of sodium salt ionize better in alkaline conditions than in acid ones. According to Hofenk de Graaff [48], fatty acid methyl ester a-sulphonates are said to be exceptions as they are stable between pH 3 and pH 10, which makes them excellent for cleaning textiles that have become acidic.Sequestering agents can act as buffers in a washing solution as they often provide mildly alkaline conditions which promote ionization of anionic surfactants. The degree of ionization depends on the presence of anions in the washing solution (e.g. hydrogen carbonate ions), which results in weakly acidic solutions, as well as the counter-ions of anionics (e.g. sodium ions), which result in strongly basic solutions. Thus, the combined use of sequestering agents with anionic surfactants may result in a wash solution of alkaline pH. If the fibres and dyes are not sensitive to alkaline conditions, there are several advantages to using a washing solution with a mildly alkaline pH for cleaning non-degraded and non-alkali-sensitive textiles. These advantages include: improving the cleaning power of the anionic surfactant; breaking down fatty soils by saponification; stabilizing anionic surfactants and neutralizing acids released into the wash bath from the textile and soiling.Non-ionic detergents do not cause a change in the pH of washing solutions because they do not ionize. They are usually effective in acid conditions. The pH of the washing (and rinsing) solutions will change throughout a wet cleaning process. Cartwright and Colombini [112] emphasize the importance of monitoring the pH of washing solutions throughout every stage of the washing process.

The role of lather (foam) in washing

The lathering (foaming) properties of a surfactant can be characterized by the volume of foam produced from a unit volume of washing agent prepared in standard conditions. Foams are dispersions of air bubbles in water, where the liquid is deformed into thin films. These films of water separate the air bubbles. Fine solid particles from the washing solution float into the foam. The relationship between the cleaning power of surfactants and their foaming properties is not close; however, surfactant foam decreases the amount of dispersed soil in the washing solution by holding soil in the foam and thereby inhibits soil redeposition. The application of foam to the surface of textiles has the advantage of 'drawing up1 the soil into the foam without lengthy soaking of the textile in the washing solution. However, this cleaning method of using foam alone has drawbacks: if too much foam is used it can be difficult to rinse out the detergent completely.Juhasz and Lelkesne Eros [76, pp. 220-6] list surfactants with good foaming properties: fatty acid soaps and primary alkyl sulphates with 12-14 carbons containing above 90% sulphate groups, sodium salts of fatty acid-methyl-taurides (e.g. Hostapon T) and sodium alkyl benzene-sulphonates provide stable foam (i.e. the foam bubbles do not collapse over time). Non-ionic surfactants (except saponin) provide much less foam than anionics.

Adsorption of surfactants to textiles and rinsing

Adsorption of surfactants is not completely reversible because anionics irreversibly chemisorb onto wool and silk, as observed by both Aickin [113] and Holt and Onorato [114]. Alkyl sulphate and alkyl sulphonate ions react through ion exchange with positively-charged amino and imino end groups of proteins. The actual number of sites available for sorption is pH dependent, increasing with decreasing pH. Aickin [115] found that up to 2.5% owf (weight of fabric) of sodium alkyl sulphate was retained by wool fibres under neutral pH conditions. He likened the alkyl sulphate ion to a colourless dye. Mauersberger [116] states that surfactants chemisorb less onto silk than onto wool and chemisorption of alkyl sulphates onto cotton is proportional to its protein content, most of which is located within the lumen. Freeland [117] warns that with longer washing time and higher concentrations, surfactants penetrate into the cells of wool cortex and into the lumen and the amorphous regions of cotton fibres. If they go deep they remain after rinsing. Holt et al. [118, 119] conclude that under normal wool dyeing conditions, anionic surfactants show good substantivity to wool. The factors that influence this are liquor ratio, length of surfactant side-chain and pH. Spei and Holzem [120] made a connection between the molecular length of anionics and their deposition in keratin fibre.Weatherburn and Bayle [121] give an overview of the subject. Surfactant affinity for the textile surface increases as the size of the hydrophobic part increases and the length of the hydrophilic head group/part decreases. The presence of a benzene ring increases the strength of the hydrophobic bonding, making rinsing more difficult. Electrolytes reduce the electric double layer at the liquid/solid interface, thereby increasing the adsorption of anionic surfactants.Rhee and Ballard [122-4] investigated the adsorbance of the anionic Orvus WA and reported that wool adsorbed nine times the level adsorbed by cotton. Colorimetric test methods showed that silk adsorbed Orvus WA 2.73±0.3% owf. Depending on the length of the rinsing time and level of temperature, desorption can be encouraged. Left unrinsed, the hydrophobic character of silk significantly increased while, after thorough rinsing, its hydrophobic character was normal.The aim of rinsing is to remove the 'surfactant-soil micelles' and the remaining surfactant molecules and soil-carriers. If left in the textile, surfactants and soil carriers, such as SCMC, attract and aid the diffusion of environmental soils as well as other deteriorating pollutants.Rinsing problems have been discussed by Hofenk de Graaff [125]. To optimize rinsing, it should be carried out at the solubility temperature of the surfactant, the soil-carrier and other constituents of the washing solution. When considering only optimum rinsing efficiency, the recommended temperature for rinsing anionic surfactants, at above 40 °C, is rather high for historical textiles

(unless sequestering agents arc added to allow the use of lower temperatures); with non-ionics a lower temperature (25-30 °C) is effective. Soil-carriers may be added to the first rinse solution if the textile is heavily soiled. At lower temperatures shorter rinsing times (to avoid saturation) and regular changes of rinse baths are required. The duration of rinsing, as with the duration of washing, depends on many factors, notably the thickness and structure of the textile, the possibility of agitation and whether rinsing is carried out in running water or in still baths. The use of hard water for rinsing may result in calcium and magnesium ions replacing soil in the 'surfactant-soil micelle' and soil redeposition may occur. Hence, the use of soft or deionized water at least in the first two rinse baths is recommended to help to prevent soil redeposition.Comparing the rinsing properties of anionic surfactants and non-ionics shows that anionics can be rinsed out more easily-due to the repelling forces between the textile and washing agent. However, the concentration of anionics in the washed textile may be rather high. Non-ionic surfactants, having long polar parts, may be bonded to the textile with considerable strength and may be impossible to remove completely. Despite this, their concentration is particularly low, so any residue in the textile will be at a very low concentration.

Use of vacuum suction in wet cleaning

Vacuum suction tables were introduced to textile conservation in the late 1970s by Perkinson [126]. Columbus [127] described the washing methods at the Textile Museum in Washington DC in 1967 and recommended the use of vacuum suction tables in wet cleaning of historical textiles. Landi [128] refers to vacuum suction tables as essential equipment for textile conservation workrooms. Smith [129], Diebholz [130], Christiensen [131], Hutchinson [132], Fletcher [133], Ashton [134] and Hackett [135] recommend this equipment for cleaning historical textiles. Howell [136] introduces the vacuum suction table of the Hampton Court Palace Textile Conservation Studio, purchased in 1994. Barnett [137] describes the use of a domestic water-extracting vacuum cleaner in the wet cleaning of carpets and tapestries. Harper [138] provides a thorough characterization of the vacuum suction table of the Textile Conservation Centre, UK, and its use for wet cleaning historical textiles. Both Maes [139] and Bosworth [140] describe tapestry cleaning by aerosol suction.A vacuum suction table has been used in Germany for wet cleaning historical textiles as presented by Helbig [141]. Keyserlingk and Vuori [142] reported the use of a custom-made vacuum wash table for wet cleaning of oversized textiles and announced the availability of the table specifications from the Canadian Conservation Institute [143].

Efficiency of washing

For research purposes, washing effectiveness has been tested using textiles soiled with standard-soil mixture, for example by Eastaugh and Stevens [144], Boring and Ewer [67, 145], Ewer and Rudolf [146], Reponen [147], Lewis [81] and Ginn et al. [148].A number of approaches has been utilized to characterize the detergent process, including correlating detergency and electrokinetic phenomena by Rutkowski [149]. Cramer [150] provides a range of methods for evaluating soil removal. The degree of cleanness of a textile can be determined by optical assessments and measuring actual soil content. Optical assessments relate to subjective visual investigation, reflectometry and the photometric and colorimetric attributes, such as whiteness, greyness, yellowness. Actual soil content is usually measured in simulation tests and include microscopic/Scanning Electron Microscopic (SEM) examination, gravimetry, solvent extraction, radiotracer methods in clay and in organic constituents, including artificial sebum. Soils such as iron oxide can be determined by chemical analysis.Eastaugh [151] tried to make a connection between percentage soil removal and detergent formulations. Radioisotope techniques are recommended by Shebs [152], while Morris and Prato [109] used X-ray fluorescence analysis as a quantitative measure for determining paniculate soil

removal from fabrics, as well as colour measurements. Meek [153] studied the action of soap and alkali alone in removing fatty dirt from fibres with a vertical microscope fitted with a reflex viewer and camera. Gentle and Muller [80] controlled the effectiveness by using a video microscope xlOO. When carrying out experimental washing of archaeological textiles Wolf [154] used visual examination and low magnification photography, as well as SEM, the latter also used by Obendorf [155, 156], and Pradhan [157]. Cooke et al. [158] carried out a research program studying the efficiency of four different cleaning systems for degraded linen, using ob]ective colour measurement to assess soil removal and colour change, tensile testing to estimate changes in strength, image analysis to measure changes in fibre and yarn diameter and yarn spacing, weight loss and SEM to assess soil removal and fibre damage.Walker [43] reports on the first studies of spectrophotometric techniques that measured the differences in light remission between soiled and cleaned textiles. Colour measurement with a spectrophotometer before and after washing and calculation of changes in colour (delta E values), whiteness, lightness/darkness or yellowness, including the comparison of the colour of a textile to the Grey Scale, serve to draw conclusions about cleaning effectiveness. These techniques have been applied widely to monitor washing effectiveness, for example by Boring and Ewer [148], Reponen [146] and Rhee and Ballard [123]. However, Kissa [159] found that the delta E of remission often does not correlate with the degree of soil removal.The washing effect is normally expressed by comparing the 'whiteness' of a textile before and after treatment. The degree of 'whiteness' of a fabric can be determined by measuring the ultraviolet/visible reflectance spectrum of the textile. The percentage of light reflected from a textile can be compared to a standard of magnesium oxide [48]. The reflectance values of treated and untreated samples can be compared in the same way. Shashoua [62, 160] measured both the percentage reflectance of light at 500 nm and at the wavelength of maximum reflectance (colour of the fabric) before and after cleaning. The washing power was mathematically calculated and it was found that the higher the reflectance, the more effective the washing.

Effect of washing on fibres and textiles

Tensile strength testing has been used to measure the residual strength of textiles. Wolf and Hughes [154] did not find significant differences between washed and unwashed yarns. Burgess [161] compared the long-term stability of naturally aged cotton textile fibres washed in distilled-deionized water, tap water and solutions of calcium bicarbonate (20 ppm) and calcium sulphate (20 ppm), using gel permeation chromatography and viscosimetry. On the basis of the result of measuring the degree of polymerization (DP) of cellulosic fibres before and after treatment and accelerated ageing she-found that fibres washed with distilled-deionized water or calcium bicarbonate solution showed greatly increased deterioration relative to the control. Hutchins [162] investigated the effect of wet cleaning on cotton by measuring weight change, stating that part of the decrease in weight after washing comes from the dissolved deterioration products, while, with the aid of SEM, Pradhan observed dirt particles disappearing from the surface of the fibres after washing [163]. Wallenborg examined changes in dimensions, weight, colour, pH, fibre and chemical deposits on the surface on seventeenth century cotton [164].Golikov and Ustinov [165] carried out microscopic investigations on fibres to establish an appropriate cleaning solution. Asnes [166] illustrates damage to cotton fibres after wet cleaning treatments using SEM micrographs. Hansen and Derelian describe the effects of wet cleaning on silk tapestries. Based on measuring tensile properties, they found '...silk threads of tapestries which became significantly stronger following the washing procedure, but it is extremely unlikely for this to be a random occurrence' [167, p. 9S\. Their study did not address the effect of water on long-term strength or the negative effects of swelling of fibres.

Washfastness and colour change of dyes

Masschelein-Kleiner [168] investigated the solubility of colourants in washing solutions. According to Duff et al. [169], the washfastness of dyes is determined by several factors, such as the strength of the bonds between the dye and the fibre, the size, shape, and levelling characteristics of the dye, the pH and the actual composition of the washing solution, the temperature and duration of the treatment and the mechanical treatment during washing. In the American Standard [170] five classes can be used for characterizing washfastness: 1 very poor, 2 poor, 3 fair, 4 good, 5 excellent. Tíimár-Balázsy and Eastop [17] give a short overview on the washfastness of direct, acid, basic, mordant and vat dyes.Wentz [73] dyed wool with natural colorants (alkanet, annato, brazilwood, cochineal, cutch, henna, indigo, lac dye, logwood, madder, weld) to investigate their colour change and washfastness during wet cleaning. The colour change ratings were obtained by visually comparing the dyed samples after treatment with the American Association of Textile Chemists and Colonsts (AATCC) Grey Scale for colour change. The staining rates (i.e. degree of bleeding) were made on the white fabrics by using the AATCC Grey Scale for staining. The findings led to the conclusion that the anionic sodium alkyl sulphate surfactant Orvus WA and the non-ionic ethoxylated nonylphenol surfactant, Tergitol NPX, do not cause significant colour changes or staining with the natural colourants tested.Daniels [171] gives a detailed explanation of the reasons for colour change of a number of natural dyes in various pH conditions. Vago [172] reports on the serious colour change of a cochineal dyed wool garment during the cleaning of its silver braiding with sodium hydrogen carbonate solution. The red colour turned to violet due to the change of pH into the alkaline region [17, pp. 143-6].Dirks [173] describes the thorough washfastness testing of an American quilt and the use of the results in the decision-making concerning its treatment. Bruselius-Scharff [174] not only provides a detailed evaluation on the washfastness of synthetic dyes occurring on historical textiles but also makes suggestions for the treatment of bleeding dyes. Oger [175] investigated the washfastness of modern direct dyes on support fabrics and yarns used for conservation and found that they bleed considerably in washing; the use of these colourants appears to be incompatible with the practical requirements of restoration and conservation.

Biodegradation of surfactants

The ease with which surfactants degrade plays an important role in their selection as concern about their long-term environmental effects increases. An overview on the connection between surfactants and environment has been published by Thomas [176] in 1999. Towards the end of the twentieth century serious doubts about the biodegradability of alkyl phenol ethylene oxide non-ionic surfactants have been expressed, noted, for example, by Davidson and Milwidsky [49, pp. 185-7]. It appears that fatty alcohol ethoxylates are biodegradable but this reduces somewhat with increasing amounts of ethylene oxide. Schick [177] opposes the use of alkyl phenol ethoxylates because of health consequences, slow biodegradation and relative difficulty of rinsing out. In an unpublished typescript Potter [178] highlighted the possibility of banning Synperonic N in the UK as early as 1992 and Gentle and Muller [80] report that the use of Synperonic N was first banned in Sweden due to its partial biodegradability. Nonylphenols have been identified as oestrogenic compounds, which have been linked to both male infertility and breast cancer. Daniels [179] also calledconservators attention to the necessity of replacing Synperonic N and NDB.A risk assessment of using nonylphenol ethoxylates is provided by Weeks et al. [180] and the problems relating to the sorption of nonylphenol ethoxylates are discussed by Hayward and Allen [181]. Swisher [182] provides an overview of the connection between the chemical structure and surfactant biodegradation: one conclusion was that the linearity of the hydrophobic group is an important factor. Linear surfactants are highly biodegradable, highly branched ones are not. The effect of a single methyl branch in an otherwise linear molecule is barely noticeable; however, increased resistance to biodegradability with increased branching is generally observed, particularly

by terminal quaternary branching. The nature of the hydrophilic group has only a minor influence on the biodegradibility. The clearest examples of such influence are seen in LPAS, which undergoes biodegradation significantly faster than other amonics and the polyethoxylate non-ionics, where biodegradation is promoted by shorter EO chain length. Increased distance between the sulphonate group and the far end of the hydrophobic group increases the speed of biodegradation. This is known as the distance principle. According to Swisher [182], the problem with alkylphenol ethoxylates (such as Synperonic N) is that the phenol is towards the centre of the molecule. APEs readily undergo biodegradation when the phenol is linked to the hydrophobic chain at, or near, the end. Ethoxylates of linear fatty acids and fatty amides are easily degraded even with ethoxylation as high as EO=20. The use of a sugar as the hydrophilic group does not result in any spectacular improvement in biodegradability, but falls in line with the usual principles.

Selected case histories using surfactants and other wash bath additives

Naithani and Kharbade [183] give a valuable overview on the aqueous cleaning methods of historical textiles. Gentle and Muller [80] followed a repeated sequence of washing and rinsing when carrying out washing of historical textiles for research purposes. Case histories on wet cleaning of archaeological textiles have been published by Flury-Lemberg [37], Hillyer [184] and Nagy [185]. Methods of wet cleaning of historical textiles are described by Rice [186], Finch and Putnam [187, 188], Masschelein-Kleiner [189], Landi [129] and Pertegato [190, 1911. Landi [192] may have been the first to introduce a modern washing table to textile conservation laboratories in a paper published 1966. Results of thorough research into wet cleaning of historical textiles is provided by Gunilla [193, 194]. Schneider [195] reports on removing 114g soiling (and possibly, in the present author's opinion, deterioration products of fibres) from a sacred coat by wet cleaning. The 'routine' wet cleaning methods of the Baltimore House Textile Conservation Workshop were discussed by Wolf et al. [196]. Behar [197[ gives an overview and flood and bath washing is described by Howard [198] for wet cleaning carpets. The use of foam from Hostapon T is common in the Abegg-Stiftung, Swit7.erland, and in many other workshops. Pataki [199] reports using the foam of a 0.5 g/litre Hostapon T anionic surfactant solution for cleaning a historical textile.Washing of large textiles is a particularly difficult task, as reported by Fikioris [200], Davies [97], the Textile Studio, Hampton Court [201], Keyserlingk [202], Haldane [203] and Marko et al. [204]. Collins [205], for example claims that the soaking of the headquarters tent of George Washington took 65 hours to loosen mud stains and other soil.

Conclusions

It is natural that a literature review also provides a historical overview. Publications on textile conservation from the 1950s and 1970s show the strong influence of industry on the surfactants and other ingredients used in wash baths for historical textiles. Working with conservators, scientists entering conservation from an industrial background, sooner or later recognized the limits in the use of the enormous number of different washing agents available and applicable to industry. Research in the 1980s and 1990s resulted in wash bath recipes much more closely tailored to conservation.However, there are several 'grey areas', such as the connection between critical micelle concentration, cloud point and Krafft point; how to determine the remained adsorbed surfactant in the washed historical textile (in September 2000 Howell and Carr [206] presented a promising new method using X-ray Photoelectron Spectroscopy); or simply, what is the appropriate washing time.After finding appropriate surfactant and washing solution compositions, many workshops started to use predominantly one type of surfactant routinely (see the popularity of Orvus WA in the USA and Synperonic N in the UK), despite there-being many varied surfactants available and recommended in the conservation literature. The method of choosing particular surfactants and washing solutions according to the specific need of the object to be treated, or using them in combination is still rare.

Fast dissemination of information is characteristic of recent years but not of the past: although Rice published on the use of amomc detergent in the first, and non-ionic in the second wash bath in 1966 [95], it was only in 1995 that Gentle and Muller systematically researched the use of mixtures of amonics and non-ionics in the same wash bath [80]. Dating from 1995, Walker's recommendation to start with a lower, and end with a higher HLB surfactant in a two-step washing process seems to have had little influence on the textile conservation field [43].The environmental concerns, both relating to conservators' health and the biodegradability of surfactants, necessitated new researches in this field, not for the purposes of the conservation of historical textiles, but for the conservation of human beings and their environment. It is true that there are negative remarks on the health effects and slow biodegradability of some popular surfactants in specialist literature before Schick's work of 1966 [177]; however, the first warning relating to the use of nonlyphenol ethoxylates in the field of textile conservation came from Potter in 1992 [178], followed by Gentle and Müller's 1995 thesis [80] and ending with Daniels' dramatic announcement in 1999 [179]. Now, as increasing numbers of conservators and scientists are searching for a replacement for Synperonic N, it should be asked why it took such a long time to start dealing seriously with the problem. Also, it may be questioned, as didHowell [206], whether the very small quantities, which are used highly diluted in textile conservation, are really the cause of such a serious problem or if this is much more a problem for industry.In conclusion, the author hopes that the above review shows the importance of studying the 'industrial' literature, of allowing enough time for a thorough conservation-related 'critical' adaptation and of being sufficiently fast in following initiatives towards new research.

References

1 Dunan-Rees, $., 'The cleaning of historic textiles -methodological and scientific aspects' in Pertegato, F., ed., Conservation and Restoration of Textiles Proceedings of the International Conference, Coino 1980, CISST-I.ombardy Section, 1982, pp. 191-6.2 Eastop, D. and Brooks, M., 'To clean or not to clean?' in Bridgland, J., ed., Preprints of the 1 lth Triennial Meeting of the ICOM Committee for Conservation, Edinburgh, James & James, London, 1996, pp. 687-91.3 F.astop, D. and Brooks, M., 'Difficult decisions in cleaning: the evidental value of soils and creases' in 2. Ehemaligentreffen der Ahegg-Stiftitng, Referate der Tagung, November 1996, Abegg-Stiftung, 1996, pp. 10-19.4 Hall, R. and Barnett, J., 'A fifth dynasty funerary dress in the Petne Museum of Egyptian Archaeology: its discovery and conservation', Textile History 16, no. 1, 1985, p. 12.5 Dodds, W.| 'Consolidation of mud on a World War I uniform', Australian Institute for the Conservation of Cultural Material (AICCM) Newsletter 25, 1988, p. 7.6 Brooks, M., Clark, C, Eastop, D. and Petschek, C, 'Restoration and conservation - issues for conservators', in Oddy, A., ed., Restoration: Is it Acceptable?, British Museum Occasional paper 99, Department of Conservation, London, 1994, pp. 103-22.7 Brooks, M., Lister, A., Eastop, D. and Bennett, T, 'Artefact or information? Articulating the conflicts in conserving archaeological textiles' in Roy, A. and Smith, P., eds., Archaeological Conservation and its Consequences, Preprints of the Contributions to the IIC Congress, Copenhagen, IIC, London, 1996, pp. 16-21.8 Johansen, K., 'Perfumed garments, their preservation and presentation '...the good smell of old clothes" in Bridgland, J., ed., Postprints of the 12th Triennial Meeting of the ICOM Committee for Conservation, Lyon, James & James, London, 1999, pp. 637-42.9 Stauffer, A., 'Some comments on the cleaning of archaeological textiles' in Timar-Balazsy, <;. and Eastop, D., eds., International Perspectives on Textile Conservation, Archetype, London, 1998, pp. 159-61.

10 Windsor, D., 'To clean or not to clean' in Ewer, P. and McLaughlin, B., eds., Postprints of the AlC-Textile Speciality Group Meeting, AIC, 1995, pp. 39-50.1 1 Timar-Balazsy, A., Matefy, Gy. and Csanyi, S., 'Effect of stains and stain removal methods on historical textiles' in Bridgland, J., ed., Preprints of the 10th Triennial Meeting of the ICOM Committee for Conservation, Washington DC, James & James, London, 1993, pp. 330-5.12 Akar, A., The Soiling of Textile Materials, M.Phil, thesis., University of Leeds, 1972, pp. 5-A, unpublished typescript.13 McKinnon, A.J. and McLaughlin, J.R., 'The dependence of carpet soiling on fibre properties, soil composition, and carpet construction' in International Wool Textile Research Conference Proceedings no 3, 1985, pp. 336-45.14 Patterson, H.T. and Grindstaff, T.H., 'Soil release by textile sutfactants' in Schieck, M.J., ed., Surface characteristics of fibers and textiles, Fiber Science Series 7, Marcel Dekker, 1995-1997, Chapter 12, pp. 448-94.15 Povve, W.C., 'Laundry soils' in Cutler, W.G. and Davis, R.C., Detergency, Theory and Test Methods, Part 1, Surfactant Science Series 5, Marcel Dekker, 1972, p. 38.16 Weber, R., Lohr, A. and Boggering, H., 'Waschen und Pflegen von Textilien aus Chemifasern', Melliand Textilbenchtc 1, 1981, pp. 94-101.17 Timar-Balazsy, j. and Eastop, D., Chemical Principles of Textile Conservation, Butterworth-Heinemann, London, 1998.18 Armstrong, J.G., Dowd, D.G., Pike, M.V. and Stitt, S., 'A furnace puff-back: the unique problem of soot on objects and costumes' in Preprints of Papers Presented at the Ninth Annual Meeting, Philadelphia, AIC, 19X1, pp. 10-19.19 Carter, J.W., 'Iron stains on textiles: a study to determine their nature and to evaluate current treatments' m de Froment, D., ed., Preprints of the 7th Triennial Meeting of the /COM Committee for Conservation, Copenhagen, ICOM with the J. Paul Getty Trust, 1984, pp. 84.9 11-14.20 |ordan, E., 'Entfernung von Kalkverputz aus einer mittelalterichen Wollstickcreis und ihre Restaurierungsproblematik', Arbeitsblatter fiir Restauratoren 21, no. 2, 1988, pp. 106-10.21 Hutchms, J., The soluble components of degraded cellulose, M.Sc. thesis, North Carolina State University, School of Textiles, 1981, unpublished typescript.22 Hersh, S.P., Hutchins, J., Kerr, N. and Tucker, P.A., 'The soluble components of degraded cellulose' in Pertegato, F., ed., Conservation and Restoration of Textiles. Proceedings of the International Conference, Como 1980, CISST-Lombardy Section, 1982, pp. 87-95.23 Andrasik, I., 'Oxidized oil stains', IFI Bulletin: Technical, International Fabncare Institute, 1986, p. 2.24 Moreland, B., 'Oxidized oil stains', IFI Fabncare News 16, no. 12, December 1987, p. 14.25 Caneva, G., Nugari, M.P. and Salvadori, O., Biology in the Conservation of Works of Art, ICCROM, 1991, pp. 60-1.26 Ballard. M.W., 'The removal of crosslinked synthetic latex from carpets: preliminary results' in Bridgland, J., ed., I'ostpnnts of the 10th Triennial Meeting of the ICOM Committee for Conservation, Washington DC, James & James, London, 1993, pp. 331-8.27 Rice, J.W., "The characteristics of soils and stains encountered on historic textiles, Principles of Textile Conservation Science no. V Textile Museum Journal, December 1964, pp. 8-17.28 Matteini, M., Tosini, I., Giorgi, M. and Palei, G., ' Evaluation of possible methods of cleaning the Opus Anglicanum cope of Pope Pius II' in Bridgland, J., ed., Preprints of the 12th Triennial Meeting of the ICOM Committee for Conservation, Lyon, James & James, London, 1999, pp. 625-30.29 Moncrieff, A. and Weaver, G., Cleaning, Science for Conservators, Book 2, Crafts Council, London, 1983.30 Hofenk de Graaff, J., 'Detergents and their function in washing old textiles' in ICOM Committee for Museum Laboratories, Brussels, 1967, 22 pp.

31 Kissa, E., 'Kinetics and mechanisms of detergency Part III: Effect of soiling conditions on particulate soil detergency', Textile Research Journal 49, no. 7, July 1979, pp. 384-9.32 Saito, M., Otani, M and Yabe, A, 'Work of adhesion of oily dirt and correlation with washabihty', Textile Research Journal 55, no. 3, March 1985, pp. 157-64.33 Smith, S. and Sherman, P.O., 'Textile characteristics affecting the release of soil during laundering Part I: A review and theoretical consideration of the effect of fiber surface energy and fabric construction on soil release', Textile Research Journal 39, no. 5, May 1969, pp. 441^4.34 Rice, J.W., 'The wonders of water in wet cleaning, Principles of textile conservation science VI' Textile Museum Journal 2, no.l, December 1966, pp. 15-22.35 Cooke, B. 'Creasing in ancient textiles', Conservation News 35, 1988, pp. 27-39.36 Flury-Lemberg, M., 'The care of historic fabrics illustrated by the grave garments of Sigismondo Pandolfo Malatesta' in Pertegato, E, ed., Conservation and Restoration of Textiles. Proceedings of the International Conference, Como 1980, CISST-Lombardy Section, 1982, pp. 202-7.37 Flury-Lemberg, M., Textile Conservation, Abegg-Stiftung, 1988.38 Rice, J.W. 'Dry cleaning versus wet cleaning for treating textile artifacts', Bulletin of the American Group-IlC 12, no. 2, April 1972, pp. 50-5.39 Torracca, G., Solubility and Solvents for Conservation Problems, ICCROM, 4th'edn, 1990, p. 57.40 Seth-Smith, A. and Wedge, T., 'Animal glue removal from 16th century Flemish tapestry fragments: a comparative study of three cleaning methods', Conservation News 59, March 1996, pp. 65-7.41 The Guild of Cleaners and Launderers, An Introduction to Laundry Chemistry, The Guild of Cleaners and Launderers, SM/4954/1, 1986, pp. 4-5.42 Hofenk de Graaff, J., 'The constitution of detergents in connection with the cleaning of ancient textiles', Studies in Conservation 13, 1968, pp. 122-41.43 Walker, D.E., 'Surfactants in textile conservation' in Ewer, P. and McLaughhn, B., eds., Postpnnts of the Conference of the AlC-Textile Speciality Group, AIC, 1995, pp. 29-34.44 Arai, H., 'Study of detergency I. Effect of the concentration and the kind of detergent in hard water', Journal of the American Oil Chemists' Society 43, May 1966, pp. 312-14.45 Bede, D., 'Water - what about it?' in Ewer, P. and McLaughlin, B., eds., Postpnnts of the Conference of the AIC-Textile Speciality Croup, AIC, 1995, pp. 9-11.46 Heald, S., 'Deiomzed water and its reactivity — could it be damaging?' in Ewer, P. and McLaughlin, B., eds., Postprtnts of the Conference of the AIC-Textile Speciality Group, AIC, 1995, pp. 12-14.47 Phenix, A. and Burnstock, A. 'The removal of surface dirt on paintings with chelating agents', The Conservator 16, 1992, pp. 28-38.48 Hofenk de Graaff, ]., 'Some recent developments in the cleaning of ancient textiles' in Bromelle, N.S. and Thomson, G., eds., Science and Technology in the Service of Conservation, IIC, London 1982, pp.93-9549 Davidson, A. and Milwidsky, B., Synthetic Detergents, George Godwin Ltd, London and John Wiley & Sons, New York, 6tn edn, 1978.50 Neiditch, O.W., 'Definition of terms Chapter V in Cutler, W.G. and Davis, R.C., Detergency. Theory and Test Methods, Part 1, Surfactant Science Series 5, Marcel Dekker Inc., 1972, p. 9.51 Moore, M.A., Detergents, A Unilever Educational Booklet, Revised Ordinary Series no. 1, Unilever Limited, 1967, pp. 3-4.52 Niven, ]un., W.W., Fundamentals of Detergency, Remhold Publishing Corporation, 1950, pp. 45-8.53 Durham, K., Surface Activity and Detergency, Macmillan & Co. Ltd, London, 1961, pp. 26-7.54 Jakobi, G. and Lohr, A., Detergents and Textile Washing, Principles and Practice, VCH Verlagsgesellschaft, Weinheim, 1987.

55 Linfield, W., ed., Anionic Surfactants, Surfactant Science Series 7, Marcel Dekker Inc., 1976.56 Schick, M.J., ed., Noniomc Surfactants, Surfactant Science Series 1, Marcel Dekker, 196657 Hofenk de Graaff, J., 'Some thoughts about cleaning ancient textiles' in Symposium Conservation of Flags, Rijksmuseum, Amsterdam, 1977, IAMAM-Textielcommissie Musea, 1980, pp. 109-1158 Smith, D.L., Matheson, K.L. and Cox, M.F., 'Interactions between linear alkylbenzene sulfonates and water hardness ions III Solubilization and performance characteristics of Ca(LAS)7', Journal of the American Oil Chemists' Society 62, no. 9, September 1985, pp. 1399^102.59 Takami, M., Funon as a cleaning agent for historic textiles: a preliminary investigation of its surfactant properties and cleaning effect, Diploma Thesis, The Textile Conservation Centre, University of Southampton, Winchester, 2000, unpublished typescript.60 Embree, J.L., 'Wash day woes of the textile conservator: laundry methods of the turn of the century', Ars Textrina, Journal of Textiles and Costume XXIII, August 1995, pp. 73-95.61 Cam;., C, "Traditional techniques used for cleaning, restoring and caring for textiles in the 19th and 20th centuries', Bulletin of the Institute for the Conservation of Cultural Material, Australia 9, nos. 1 and 2, 1983, pp. 43-67.62 Shashoua, Y., 'Investigation into the effects of cleaning natural, woven textiles by aqueous immersion' in Grimstad, K., ed., Preprints of the 9th Triennial Meeting of the ICOM Committee for Conservation, Dresden, ICOM, 1990, pp. 313-18.63 Czerwinske, P., Der Einsatz von Saponin zuf Reinigung histonscher Seidenstoffe, Diploma Thesis, Fachhereich Restaurierung und Konservierung von Kunst- und Kulturgut der Fachhochschule Koln, 1997, unpublished typescript.64 lsu]ii, K., Surface Activity. Principles, Phenomena, and Applications, Academic Press, 1998, p. 4 I.65 Dillan, K.W., 'Effects of the ethylene oxide distribution on nonionic surfactant properties', Journal of the American Oil Chemists' Society 62, no. 7, July 1985, pp. 1 144-51.66 Porter, M.R., Handbook of Surfactants, Blackie Academic & Professional, 1991, reprinted, 1993, pp. 42-45.67 Boring, M. and Ewer, P., 'Surfactant comparison test' in Krueger, J., ed., Proceedings of the Paintings and Textiles Specialty Croups Joint Session, A1C, 1991, pp. 41-61.68 Delcroix, G. and Bureau, C, 'A new detergent formulation' The Textile Museum Journal 29 and 30, 1990-1991, The Textile Museum, 1991, pp. 59-64.69 Bigler, N., Netzen und Waschen, Ciba-Geigy Rundschau, Die Tenside, 1971-2, pp. 24-32.70 Ward, T.L. and Benerito, R.R., 'Testing based on wettability to differentiate washed and unwashed cotton fibers', Textile Research Journal 55, no. 1, January 1985, pp. 41-5.71 Lange, IL, 'Physical chemistry of cleansing action1 in Shinoda, K., ed., Solvent properties of surfactant solutions, Surfactant Science Series 2, Marcel Dekker, 1967, pp. 1 17-88.72 Hutchinson, E. and Shinoda, K., 'Solvent properties of surfactant solutions' in Shinoda, K., ed., Solvent properties of surfactant solutions, Surfactant Science Series 2, Marcel Dekker, 1967, pp. 13-16.73 Wentz, M., 'Experimental studies on the effect of aqueous and nonaqueous treatments on historic textiles' in Needles, H.S. and Zeronian, S.H., eds., Historic Textile and Paper Materials: Conservation and Characterisation, Advances in Chemistry Series 212, American Chemical Society, 1986, pp. 211—30.74 Skagerlind, P. 'Textile cleaning with tensides and/or enzymes', Rengoring vid textilkonservering idag och i framtiden (Textile Cleaning and Conservation Today and Tomorrow), Seminar, Army Museum, Stockholm, Arme Museum Rapportsene 6, 1993, pp. 17-21.75 Taylor, R.J., Theory of Detergency, A Unilever Educational Booklet, Advanced Series, no. 7, Information Division, Unilever Limited, 1969, 16 p.

76 [uhasz, E. and Lelkesne Eros, M., Eeliiletaktiv Anyagok Zsehkonyve (Book of surface active agents), Muszaki Konyvkiado, 1979, pp. 126-38.77 Zika, El., 'Using non-ionic surfactants' Journal of the American Oil Chemists' Society 1, no. 15, 1969, pp. 26/323-31/328.78 Rice, J.W., 'Characteristics of detergents for cleaning historic textiles. Principles of textile conservation science, No. VII', Textile Museum Journal II, no.l, 1970, pp. 23-7.79 Kissa, E., 'Kinetics of soil release', Textile Research Journal 41, September 1971, pp. 760-7.80 Gentle, N. and Muller, S., 'An initial studv of detergents and washing recipes for use in the conservation of textile objects', Conservation Neivs 58, November 1995, pp. 55-9.81 Lewis, J., Summary of an investigation into mixtures ofanionic and nonionic surfactants for wet cleaning historic textiles, Diploma Thesis, The Textile Conservation Centre, Courtauld Institute of Art, London, 1996, unpublished typescript.82 Brochure 6431 D, Ciba Geigy, 1 p. and Description of Kieralon OLB, BASE, 3pp.83 Stupel, EL, Synthetische Wash- and Reinigungsmittel, Koradin Veiiag, 1957.84 Jones, T.G., 'Dirt removal', chapter 4 in Cutler, W. and Kissa,E., eds., Surface Activity and Detergency, Macmillan & Co. Ltd, London, 1961, pp. 72-118.85 Harris, [. C, 'Detergency', m Schick, M.J. ed. Nonionic surfactants, Surfactant Science Series 1, Marcel Dekker, 1967, p. 706.86 Schonfeldt, N., Surface Active Ethylene Oxide Adducts, Pergamon, Oxford, 1969, pp. 386-441.87 Smith, AAV. and Lamb, M.H., 'The prevention of soil redeposition in the cleaning of ancient textiles' in Preprints of the 6th Triennial Meeting of the ICOM Committee for Conservation, Ottawa, 1981, pp. 81/9/4-1.HH Lchmann, D., 'Restaurieren und Konservieren histonscher lextilen , Arbeitsblatter fiir Restauratoren, 1/74, Gruppe 10, Textiiien, pp. 27-33.89 Wveth, P., Research Proposal, Internal Report, The Textile Conservation Centre, Courrauld Institute of Art, London,1996, unpublished typescript.90 Collins, M., How to wet clean uudyed cotton and linen, Smithsonian Institution, Museum of History and Technology textile Laboratory, Washington DC, Information Leaflet 478, 1 967, 1 1 pp.91 Hogberg, S., 'Cleaning silk velvet', Sb'T-Jubilee Conference, Silk - Different Aspects, Svenska Foreningen for Textilkonservering,1997, 3 pp.92 Daniels, V. and Shashoua, Y., 'Wet cleaning of paper and textiles: similarities and differences' in Butterfield, E and Eaton, L., eds., Paper and Textiles. The Common Ground. Preprints of the Conference held at The Burrell Collection, Glasgow, SSCR, 1991, pp. 19-24.95 Canadian Conservation Institute, Washing non -coloured textiles, CCI Notes 13/7, CCT, Ottawa, 1st printing 1986, 2nd printing 1988; Anionic Detergents, CCI Notes 13/9, CCT, Ottawa, 1983.94 Mofatt, E., Detergents, CCI Report ARS no. 1781, CCI, Ottawa, 1981.95 Rice, |.W., 'An heirloom patchwork quilt and its conservation problems', Studies in Conservation 11, no.l, February 1966, pp. 1-7.96 Cox, M.E, Borys, N.E and Matson, T.P., 'Interactions between LAS and nonionic surfactants', Journal of the American Oil Chemists' Society 62, no. 7, July 1985, pp. 1139-43.97 Davies, V, 'Wet cleaning of the dining room curtains Uppark House' and 'Wet cleaning of the small drawing room curtains Uppark House' in Marko, K., ed., Textiles in Trust, Archetype in association with the National Trust, London, 1997, pp. 159-63 and 164-7.98 Elofenk de Graaff, J., 'Cleaning ancient textiles' in Pertegato, E, ed., Conservation and Restoration of Textiles. Proceedings of the International Conference, Coma 1980, CISST-Lombardy Section, 1982, pp. 62-65.

99 Giuntmi, C. and Bede, D. 'The conservation of a group of paracas mantles' in Stefanaggi, M., ed., La Conservation des Textiles Ancieus, Journees d'ftudes de la SFIIC, Angers, SIIEC, 1994, pp. 169-79.100 Kajitani, N., 'A retrospective of 1973 conservation treatment on a Munghal court robe with the pigment-painted poppy flower pattern' in Paulocik, C. and Flaherty, S., eds., The Conservation of 18th century painted silk dress, The Costume Institute, The Metropolitan Museum of Art and the Graduate Program in Costume Studies, New York University, 1995, pp. 118-29.101 Zongyou, E, 'The preservation of textile unearthed from N. 1 Mausoleum of King Qin in Feng Xiang County of Saanxi Province' in Proceedings of the EEC China workshop on preservation of cultural heritages. Xian, Shaanxi, P.R. of China. September 25-30, 1991, Teti, Napoli, 1992, pp. 423-30.102 Kiefer, K., 'Interdisciplinary philosophies: Textiles and Paper: a Common Ground' in The AIC Textile Specialty Group Postpnnts, AIC, 1994, pp. 7-15.103 Cusseil, S., 'Different methods or different choices' in Ti'mar-Balazsy, c. and Eastop, D., eds., International Perspectives on Textile Conservation, Archetype, London, 1998, pp. 108-10.104 Glover, J.M., 'Textile conservation in North West England' m Pertegato, F., ed., Conservation and Restoration of Textiles. Proceedings of the International Conference, Cotno 1980, CISST-Lombardy Section, 1982, pp. 208-14.105 Burgess, H., Duffy, S. and Tse, S., 'Investigation of the effect of alkali on cellulosic fibres Part 1: rag and processed wood pulp paper' in Butterfield, F. and Eaton, I.., eds., Paper and Textiles. The Common Ground. Preprints of the Conference held at The Burell Collection, Glasgow, SSCR, 1991, pp. 29-47,106 Hofenk de Graaff, J., personal communication, 1991.107 Shenai, V.A., 'Organic textile chemicals - historical introduction', Textile Dyer & Printer, 28 December 1988, pp. 15-19.108 Maison Chevalier, Aubusson, Rapport de Stage: 'Determination de la concentration ideale de detergent pour le nettoyage d'un textile histonque', Christophe Bureau Ecole Normale Superieure, 1988, 25 pp.109 Morris, M.A. and Prato, H.H., 'The effect of wash temperature on removal of paniculate and oily soil from fabrics of varying fiber content', Textile Research Journal 52, no. 5, April 1982, pp. 281-6.110 Hewitt Myers, G., 'Principles of practical cleaning for old and fragile textiles', Museum News Technical Supplement 6, February 1965, pp. 50-2.111 Howell, D. and Farnsworth, J., 'Operation Wetclean - a review, Operation Wetclean — an analysis of results1, Conservation News 72, July 2000, pp. 53-6.112 Cartwright, H. and Colombini, A., 'Detergent monitoring during the washing process at the Iextile Conservation Studios, Hampton Court Palace' in Bridgland, J., ed., Preprints of the 10th Triennial meeting of the ICOM Committee for Conservation, Washington DC, 1993, pp. 293-8.113 Aickin, R.G., 'Communication: the adsorption of sodium alkyl sulphates on wool and other textile fibers', Journal of the Society of Dyers and Colounsts 60, no. 3, March 1944, pp. 60-5.114 Holt, L.A. and Onorato, J., 'Substantivity of various anionic surfactants applied to wool', Textile Research Journal 59, no. 11, November 1989, pp. 653-7.115 Aickin, R.G., 'The adsorption of sodium alkyl sulphates on wool and other textile fibres', Journal of the Society of Dyers and Colounsts 60, no. 10, October 1944, pp. 266-87.116 Mauresberger, H., ed., Textile Fibres, Wiley and Sons, 1947, p. 269.117 Freeland, G.N., Guise, G.B. and Russel, I.M., 'Sorption and analysis of some nonylphenol ethoxylate surfactants on wool', Textile Research Journal 55, no. 6, June 1985, pp. 358-62.118 Holt, L.A., Kelson, J.S., and Reddie, R.N., 'Substantivity of various anionic surfactants applied to wool. Part I and II', Textile Research Journal 59, 1989, pp. 553-657.119 Holt, L.A., Kelson, J.S., and Reddie, R.N., 'Substantivity of various anionic surfactants applied to wool. Part I and IP, Textile Research Journal 62, no. 3, March 1992, pp. 141-143

120 Spei, M. and Holzem, R., 'Molecular length dependent deposition of sodium alkyl sulphates in keratin fibre', Melliand Textilhenchte 9, 1990, E329, 71, pp. 706-7.121 Weatherburn, A.S. and Bayle, C.H., 'The sorption of synthetic surface active compounds by textile fibres', Textile Research Journal 22, December 1952, pp. 797-804.122 Rhee, H. and Ballard, M., 'The chemical interaction of surfactants with fibres, especially with silk' in Postpnnts of the Meeting of the AlC Textile Specialty Group, AIC, 1993, pp. 28-37.123 Rhee, H. and Ballard, M., 'Residues of surfactant on silk' in Bfidgland, J., ed., Preprints of the 10th Triennial meeting of the ICOM Committee for Conservation, Washington DC, 1993, pp. 327-9.124 Ballard, M.W. and Rhee, H., "The effect of surfactant residues on silk' in Svenska Foremngen for Textilkonservenng Jubilee Conference. Silk - Different Aspects, SET, 1997, 6 pp.125 Hofenk de Graaff, personal communication, 1996.126 Perkinson, R.L., 'Design and construction of a suction table',Journal of the American Institute for Conservation 20, nos. 1 and 2, 1981, pp. 36-40.127 Columbus, J.V., 'Washing techniques at the Textile Museum', IIC-AG Bulletin 7, no. 2^ 1967, pp. 14-16.128 Landi, S., The Textile Conservator's Manual, Butterworth-Heinemann, London, 2nd edn, 1992, pp. 39 & 93-5.129 Melville Smith, L., 'Conservation practices at the Museum of Fine Arts, Boston' in Pertegato, F., ed., Conservation and Restoration of Textiles Proceedings of the International Conference, Cotno 1980, CISST-Lombardy Section, 1982, pp. 251-8.130 Driebholz, V., 'The use of suction table in textile and paper conservation', Report of the Textile Conservation Group 3, no. 3, December 1980, pp. 2-5.131 Christiensen, C, 'The suction table for use on paintings and textiles', AIC News 17, no. 2, 1992, pp. 1-4.132 Hutchinson, B., 'Suction table used at the Textile Conservation Lab at the Cathedral Church of St. John the Divine', Textile Conservation Group Newsletter 3, 1992, pp. 3-4.133 Fletcher, S., 'Suction for localized treatment of paper and textiles. Part I - suction techniques used on works of art on paper', report issued at the Scottish Society for Conservation and Restoration Conference, Paper and Textiles: the Common Ground, held at the Burrell Collection, Glasgow, SSCR, 1991, 8 pp., unpublished typescript.134 Ashton, M., 'Suction for delocalized treatment of paper and textiles. Part II - Variations in behaviour of paper, textiles and equipment used in suction disk treatments' in Butterfield, F. and Eaton, I.., eds., Paper and Textiles: the Common Ground. Preprints of the Conference, held in the Burrell Collection, Glasgow, SSCR, 1991, pp. 59-69.1 35 Hackett, J., Possible designs for a vacuum suction table for the textile conservation laboratory, Report, Fine Arts Museum San Francisco, 1993, 11 pp, unpublished typescript.136 Howell, D., 'New vacuum table design for use with textiles', Conservation News 54, 1994, p. 12.137 Barnett, J., 'The use of a domestic water extracting vacuum cleaner in the wet cleaning of carpets and tapestries' in Timar-Balazsy, q. and Eastop, D., eds., Ititernational Perspectives on Textile Conservation, Archetype, London, 1998, pp. 29-31.138 Harper, M.T., An Investigation into the use of vacuum suction tables for dry and wet cleaning historic textiles, Diploma Report, Postgraduate Diploma in Textile Conservation, Textile Conservation Centre and Courtauld Institute of Art, University of London, 1995, unpublished typescript.139 Maes, Y, 'Tapestry cleaning by aerosol suction' in Timar-Balazsy, f, and Eastop, D., eds., International Perspectives on Textile Conservation, Archetype, London, 1998, pp. 32-3.140 Bosworth, D., 'Wet cleaning a fragile tapestry using the de Wit system', Conservation News 65, March 1998, pp. 49-51.

141 Helbig, H., 'Einsatzmoghchkeiten fur einen Niederdrucktisch in der Textilrestaurierung', Arbeitsblatter fur Restauratoren 2/94, Gruppe 10 Textilien, 1994, pp. 200-10.142 Keyserlmgk, M. and Vuori, J., 'Wet cleaning an oversized textile on a vacuum wash table' in Postpnnts of the AIC Textile Specialty Group, AIC, 1995, pp. 79-86.143 Canadian Conservation Institute, Vacuum Wash Table, Treatment Report, appendix G, pp. 134-5, available from CCI Extension Services with the structural drawing, CCI, 1030 Innes Road, Ottawa, Ontario K1A 0M5, Canada.144 Eastaugh, N. and Stevens, D., Notes on washing solutions, The Textile Conservation Centre, Courtauld Institute of Art, London, 1986, 14 pp., unpublished typescript.145 Boring, M. and Ewer, P., 'Report on test performed to determine the optimal concentration of the surfactant Orvus WA paste for cotton' in Bridgland, J., ed., Preprints of the 10th Triennial Meeting of the ICOM Committee for Conservation, Washington DC, 1993, pp. 289-93.146 Ewer, P. and Rudolph, R., 'Report on Orvus WA paste test', Textile Conservation Newsletter 22, Spring 1992, pp. 2-5.147 Reponen, T.H., 'The effect of conservation wet cleaning on standard soiled wool fabric: some experimental work' in Bridgland, J., ed., Preprints of the 10th Triennial meeting of the ICOM Committee for Conservation, Washington DC, 1993, pp. 321-6.148 Ginn, M.E., Davis, G.A. and Jungermann, E., 'Statistical approach to detergency III. Effect of artificially soiled test cloth', Journal of the American Oil Chemists' Society 43, May 1996, pp. 317-20.149 Rutkowski, B.J., 'An electrophoretic study of the detergency process', J.O.C.S., April 1968, pp. 267-71.'150 Cramer, J.J., 'Evaluation methods for soil removal and soil redeposition. Chapter 9' in Cutler, W.G. and Davis, R.C., eds., Detergency Theory and Test Methods, Part I, Marcel Dekker, 1975, pp. 323-411.151 Eastaugh, N., 'Some experiments comparing the performance of detergent formulations based on anionic and nonionic surfactants under conditions relating to conservation use' in Grimstad, K., ed., Preprints of the 8th Triennial Meeting of the ICOM Committee for Conservation, Sydney, The Getty Conservation Institute, Marina del Rev, 1987, pp. 357-64.152 Shebs, W.T., 'Radioisotopes Techniques in Detergency' in Cutler, W.G. and Kissa, E., eds., Detergency: Theory and Technology, Marcel Dekker Inc., 1987, pp. 1-89.153 Meek, D.M., 'Microscopical studies of detergency: dirt removal from naturally soiled fibres', Textile Research Journal 57, 1966, pp. 337-43.154 Wolf, S.J. and Hughes, M.C., 'The effects of wet cleaning on dry site archaeological textiles. Results of a pilot study' in Postprints of the Meeting of the AIC Textile Specialty Group, AIC, 1992, pp. 7-14.155 Obendorf, S.K., 'Soiling and soil removal as studied by electron microscopy' m AATCC Book of Papers, 1987, pp. 279-84.156 Obendorf, S.K., 'Electronmicroscopical study of soiling and soil removal', Textile Chemist & Colorist 20, no. 5, May 1988, pp. 11-15.157 Pradhan, R.M., 'Application of scanning electron microscopy to the study of cotton fabric', Textile Industry and Trade Journal 20, May-June 1982, pp. 3-8.158 Cook, W.D., Babakhami, A. and Hillyer, I.., 'The cleaning of degraded linen, Part I and Part 11', The Conservator 20, 1996, UKIC, London, pp. 3-14.159 Kissa, E., 'Evaluation of detergency' in Cutler, W.G. and Kissa, E., eds., Detergency — Theory and Teclmology, Surfactant Science Series, Marcel Dekker, 1987, pp. 225-60.160 Shashoua, Y., 'Investigation into the effects of cleaning old, dyed; naturally soiled textiles, by aqueous immersion' in Bridgland, J., ed., Preprints of the 10th Triennial Meeting of the ICOM Committee for Conservation, Washington DC, 1993, pp. 714-20.161 Burgess, H.D., 'Ge! permeation chromatography. Use in estimating the effect of water washing on the long-term stability of cellulosic fibres' in Needles, H.L. and Zeronian, S.H., eds.,

Historic Textiles and Paper Materials: Conservation and Characterisation, Advanced Chemistry Series 212, American Chemical Society, 1986, pp. 363-76.162 Hutchins, J., 'The effect of wet cleaning on cotton', Report of the Textile Conservation Group 3, no. 1, September 1980, pp. 1-4.163 Pradhan, R.M., 'Scanning electron microscopic (SEM) study of damage to cotton fabric washed in harsh detergent formulation', Textile Industry and Trade journal 20, November-December 1982, pp. 29-30.164 Wallenborg, I., 'Twattundersokind av textil', (An examination of some methods for cleaning textiles), Meddelelser on Konservermg 3, no. 6, 1983, pp. 217-34.165 Golikov, V.P. and Ustinov, S.V., 'Complex experimental investigation of the effect of cleaning compositions on the fibres and dyes of museum textiles' in Grimstad, K., ed., Preprints of the 8th Triennial Meeting of the ICOM Committee for Conservation, Sydtiey, The Getty Conservation Institute, Marina del Rev, 1987, pp. 373-7.166 Asnes, H., 'Wet- and dry-cleaning methods for old textiles' in Reggonng vid textilkonservenng idag och i framtiden (Textile Cleaning and Conservation Today and Tomorrow), Seminar, Army Museum, Stockholm, 1993, pp. 13-16.167 Hansen, E.E and Derelian, S., 'Conservation I. Effects of wet cleaning on silk tapestries'. Museum management and curatorship 10, no. 1, 1991, pp. 93-6.168 Masschelein-Kleiner, L., 'Le nettoyage des textiles anciens', Bulletin I.R.P.A. XIII, 1971-2, pp. 215-22.169 Duff, D.G., Sinclair, R.S. and Stirling, D., 'The fastness to washing of some natural dyestuffs on wool', Studies in Conservation 11, 1977, pp. 170-6.170 American Association of Textile Chemists and Colorists, AATCC Technical Manual, AATCC, 1989, p. 535.171 Daniels, V., 'Colour changes of watercolour pigments during deacidification' in Bromelle, N.S. and Thomson, G., eds., Science and Technology in the Service of Conservation, IIC, London 1982, pp. 66-70.172 Vago E., 'Problems encountered during the restoration of a Hungarian military gala coat' in Timar-Balazsy c.. and Eastop, D., eds., International Perspectives on Textil Conservation, Archetype, London, 1998, pp. 104-7.173 Dirks, K., 'The wet cleaning of an American quilt' in Pertegato, E, ed.. Conservation and Restoration of Textiles. Proceedings of the International Conference, Como 1980, CISSTT.ombardy Section, 1982, pp. 184-7.174 Brusehus-Scharff, A., 'Synthetic dyestuffs for textiles and their fastness to washing' in Bridgland, J., ed., Preprints of the 11th Triennial Meeting of the ICOM Committee for Conservation, Lyon, James & James, London 1999, pp. 654-60.175 Oger, B., 'Fastness to light and washing of direct dves for cellulose textiles', Studies in Conservation 41, 1996, pp. 129-35.176 Thomas, H., 'Surfactants and the environment - an overview' in Karsa, D.R., ed., Industrial Application of Surfactants IV, The Royal Society of Chemistry, Cambridge, 1999, pp. 23-39.177 Schick, M.J., 'Biodegradation Chapter 29' in Schick, M.J., ed., Nonionic Surfactants, Surfactant Science Series 1, Marcel Dekker Inc., 1966, pp. 971-95.178 Potter, J., Due to EC regulations, Synperoiiic N may be banned in the future on environmental grounds. Discussing the properties of Synperoiiic N that made it so popular and what criteria will influence the choice of a replacement, Essay submitted to the RCA/V&A Training Programme, London, 1992, unpublished typescript.179 Daniels, V., 'Synperonic N and NDB', Conservation News 68, March 1999, p. 6.180 Weeks, J.A., Adams, W.J., Gumev, P.D., Hall, J.E and Naylor, C.G., 'Risk assessment of nonylphenol and its ethoxylates in U.S. river water and sediment' in Proceedings of the 4th World Surfactants Congress, Vol. 3, C.E.D., 1996, pp. 276-91.181 Hayward, M. and Allen, R., 'Napthalene', Conservation News 49, November 1992, pp. 40-3.

182 Swisher, R.D., 'Chemical structure and primary biodegradation Chapter 6' in Swisher, R.D., ed., Surfactant Biodegradation, Surfactant Science Series 3, Marcel Dekker, 1970, pp. 203-55.183 Naithani, H.K. and Kharbade, B.V, 'An overview on the considerations of cleaning of historic textiles' in Singh, T., ed., Conservation of Cultural Property in India XVIII-XX, Indian Association for the Study of Conservation of Cultural Propcrry, 1985-7, pp. 35-40.184 Hillyer, L., 'The cleaning archaeological textiles' in O'Connor, S.A. and Brooks, M.M., eds., Archaeological Textiles Occasional Papers 10, UKIC, 1990, pp. 18-21.185 Nagy, K., 'Die Tracht eines vornehmen ungarischen Madchen aus dem 16. Jahrhundert' in Ars Decorativa 7, Museum of Applied Arts, 1982, pp. 25-79.186 Rice, J.W., 'Principles of fragile textile cleaning' in Leene, J.E., ed., Textile Conservation, Butterworths, London, 1972, pp. 32-72.187 Finch, K. and Putnam, G., Caring for Textiles, Barrie cv Jenkins, 1977, pp. 46-8.188 Finch, K. and Putnam, G., The Care & Preservation of Textiles, B.T. Batsford Ltd., 1985, pp. 61-71.189 Masschelein-Kleiner, L., 'Conservation of very brittle textiles' in Pertegato, E, ed., Conservation and restoration of very brittle textiles. International Conference Como, 1980, C.I.S.S.T.-Lombardy Section, 1982, pp. 245-50.190 Pertegato, F., / Tessili. Degrade e Restauro, Nardmi Editore, 1993, pp. 64-7.191 Pertegato, F., // Restauro degli Arazzi, Nardini Editore, 1996, pp. 170-8.192 Landi, S., 'Three examples of textile conservation in the Victoria and Albert Museum', Studies in Conservation, Volume 11. Number 3, August 1966, pp. 143-159.193 Gunilla, L., Vdtrengormg av textilier (Wet cleaning of textiles), MA Thesis, Institute of Conservation, University of Gothenburg, 1988, 114 pp., unpublished typescript.194 Gunilla, L., 'Cleaning of textiles. Discussion about research and methods in conservation' in Hanssen-Bauer, F. and Kollansrud, K., eds., Consolidates and Conservation Methods, Preprints of the Nordisk Konservatorforbund XIV Congress, NKF-N, 1997. pp. 233-8.195 Schneider, J., 'Some recent textile conservation and restoration work at the Swiss National Museum Zurich' in Pertegato, F., ed., Conservation and Restoration of Textiles, Proceedings of the International Conference, Como 1980, CISST-Lombardy Section, 1982, pp. 271-5.196 Wolf, S., Ewer, P., Hutchms, J., Buonocore Kaldanv, M. and Appelbaum, B., 'Evaluating textile treatments: discussing the state-of-the-art' in Postpnnts of the AIC-Textile Specialty Group, 19th Annual Meeting, AIC, 1991, pp. 17-25.197 Behar, R., 'The cleaning and care of Oriental rugs', Hali 1,November 1978, pp. 352-4.198 Howard, S., 'An introduction to the wet cleaning of carpets' in Timar-Balazsy, A. and Eastop, D., eds., International Perspectives on Textile Conservation, Archetype, London, 1998, pp. 26-8.199 Pataki A., 'Restoration of a 16th century child's coat ('mente') belonging to the Esterhazy collection' in Bridgland, J., ed., Preprints of the 10th Triennial Meeting of the ICOM Committee for Conservation, Washington DC, 1993, pp. 314-20.200 Fikioris, M.A., 'The wet cleaning of the silk damask curtains of the Port Royal Parlor at the Henry Francis du Pont Winterthur Museum' in Pertegato, F., ed., Conservation and Restoration of Textiles, Proceedings of the International Conference, Como 1980, CISST-Lombardy Section, 1982, pp. 198-201.201 Historic Royal Palaces Textile Conservation Studio, Five Year Review 1991-1996, pp. 27-29.202 Keyserhngk, M., 'Conservation and co-operation: treatment of the tablet-woven Gondar hanging at the Canadian Conservation Institute' in Bridgland, J., ed., Preprints of the1 Oth Triennial Meeting of the ICOM Committee for Conservation, Washington DC, 1993, pp. 699-703.203 Haldane, E.-A., 'So that's why textile conservation has such a big studio: tapestry washing at the V&A', V&A Conservation Journal 32, 1990, p. 21.

204 Marko, K., Blyth, V. and Kandall, J., 'Three methods of handling and washing large tapestry hangings', The Conservator 5, 1981, pp. 1-8.205 Collins, M., Wet Cleaning the Headquarters Tent of George Washington, Report leaflet, Division of Textiles, The National Museum of History and Technology, Smithsonian Institution, Washington DC, 1967, 3 pp.206 Howell, D. and Carr, C, 'Investigation of detergent residues on historic textiles', unpublished lecture, Wet Cleaning Seminar, Textile Conservation Centre, Winchester, 14 September 2000,2 pp.

Author

Agnes Timar-Balazsy qualified as a chemical engineer. She specialized in the study of textiles, paper, leather and the synthetic polymer industry, carrying out research into textile conservation and dye analysis. In 1985 she became a Technical Doctor and was awarded a Ph.D. in 1996. She has been employed at the National Centre of Conservation / Hungarian National Museum since 1966. Since 1974 she has been teaching material and conservation science and became Head of the Faculty of Object Conservation in 1989 and a Professor in 1996. From 1991 she has also been teaching the theory, ethics and history of conservation. She has lectured extensively outside Hungary and has organized a number of international courses on the scientific principles of textile conservation. Since 1999-2000 she has been Vice-chairperson of both the ICOM Committee for Conservation and the ICCROM Council.