TSG Chapter VI. Treatment of Textiles - Section D. Aqueous Cleaning

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Contributors: Originally drafted by Jennifer Cruise, additional contributions by Jacquelyn Peterson-Grace, Daniele Pasta and Sara Ludueña.
Editors: Mary Ballard, Jennifer Cruise.
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Copyright: 2024. The Textile Wiki pages are a publication of the Textile Specialty Group of the American Institute for Conservation of Historic and Artistic Works.

The Textile Wiki pages are published for the members of the Textile Specialty Group. Publication does not endorse or recommend any treatments, methods, or techniques described herein.

THIS ENTRY IS A DRAFT

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Warnings

There are many reasons NOT to wet clean.

• Aqueous cleaning is irreversible, material will be removed from the textile that cannot be put back or retained separately
• Interactions between objects and aqueous solutions can be hard to predict
• Must prepare for intervention if unwanted changes occur
• Many textiles are significantly weaker when wet
• Dyes can bleed
• Fibers swell
• Some embellishment materials are incompatible (gelatin sequins, etc.)

Planning

Before undertaking a wet cleaning treatment, there are a wide variety of factors to consider:

• What does aqueous cleaning hope to achieve?
  • Does the textile have an overall yellow/brown “aged” appearance that aqueous cleaning could brighten?
  • Is there specific staining or soiling? Where did the discoloration come from, and is it directly related to the use-life of the object? Is there value in retaining the soiling, and what will be lost if it is removed? Does the soiling or discoloration detract from the maker/owner’s original intent?
  • Is the staining or soiling causing physical and/or chemical damage to the object? Do stained areas feel brittle in comparison to the rest of the object, are there small losses or areas of fallout in stained areas or along tide lines?
  • What might the staining or soiling be composed of? Could the object benefit from aqueous or solvent spot cleaning prior to or instead of aqueous cleaning?
• Has soiling been mechanically reduced as much as possible with a variable speed vacuum, soft brushes, or other means? See Mechanical Cleaning.
• What is the pH of the object and conductivity of the object? Do these values vary between stained and unstained areas?  How will these characteristics impact the proposed cleaning solutions? See Water Conductivity and Measuring Surface pH and Conductivity Using Water Drop and Agarose Plug Methods.
• Will all dyes be colorfast in the proposed cleaning solutions? See Spot Tests for Colorfastness.
• Are embellishments like buttons, fringe, beads or sequins also stable in the proposed cleaning solutions? Will they swell or leach materials into the textile when wet or as they dry (like fabric-covered buttons with wooden button molds)? Do they require additional stabilization (like temporarily securing fringe with nylon net) prior to wet cleaning?
• How will the textile be moved and handled when wet? Many textiles are more fragile and can become significantly heavier when wet.
• How and where will the textile be dried when aqueous cleaning is completed? See Drying, Blotting and Blocking.
• Have all solutions been prepared in advance (if possible)?

A full plan for all handling steps and materials is needed before beginning: immersion, agitation, turning, lifting, draining, blotting, blocking, drying.

Supports in the bath

• Mylar/Melinex sheet - smooth surface for lifting, blocking, drying (see drying section)
• Net layers - draining sling for moving items or top layer to protect from abrasion during sponging (note that net itself can be abrasive)
• Perforated draining surface above the base of the bath can add support and promote rapid drainage.

Treatment order

A printed textile with structural damage is temporarily stabilized between two layers of undyed nylon bobbinet, secured with basting stitches in white polyester thread. The net and stitching are removed after aqueous cleaning.

• Surface cleaning to remove loose soils, dusts, etc. is usually performed before wet cleaning, to reduce the burden of soiling in the bath and the risk of embedding soils in the weave structure of the textile. However, some fibers may be too fragile to tolerate surface cleaning without some type of consolidation.

• Spot treatments for stain removal must be planned in coordination with wet cleaning. Usually best to complete any "dry" solvent treatments prior to aqueous spot treatments and bath immersion.

• Repairs order: decide whether they should happen before or after cleaning. Cleaning may induce further damage, while new materials may "settle in" better with old if cleaning happens after they are incorporated. Some repairs should only be undertaken after wet treatments are completed, and soiling and degradation products are reduced/eliminated.
• Stitched supports (temporary): Netting envelopes or localized supports to protect weak areas during cleaning (see image).

Space and equipment

• Use the largest flat bath possible for fragile items (avoid folds, allow water to flow through and around items)
• In deeper baths, sturdy items may be "accordioned"
• Baths should be slanted for draining (note that this increases depth needs at one end of bath)

A list of published references to wash table and other wet-cleaning equipment can be found at the bottom of this page.

Water

Cleaning effects of water alone

Water is a solvent with significant cleaning ability that may be tailored to suit the needs of an object by adjusting properties including pH, conductivity, and water temperature. Water alone can dissolve polar soiling and yellow and acidic degradation products, though it does not usually interact with oily, waxy hydrophobic substances. It can improve the flexibility of textiles and provide the opportunity to address creases and wrinkles or overall distortions. As with all interventive treatment actions, the introduction of water to an object carries significant risk that must be carefully assessed (Tímár-Balázsy and Eastop 1998).

Water content and purity can be adjusted in a variety of ways. Water purification systems require periodic maintenance, the cost and frequency of which must be considered when choosing a purification system.

Water Types

Tap water is generally problematic for aqueous cleaning of cultural heritage textiles. Tap water may contain dissolved salts, acids, alkalies, fertilizers, waste products (domestic or agriculture) bacteria, fungal spores, and dissolved components of the water pipes, all of which can interfere with the cleaning process or have a detrimental impact on objects. The impact of these components is described in greater detail in Chemical Principles of Textile Conservation (Tímár-Balázsy and Eastop 1998).

Soft water contains sodium ions in place of calcium and magnesium ions in “hard” water. Soft water has better cleaning properties than hard water and does not form insoluble soap scum (Tímár-Balázsy and Eastop 1998). See also hardness (water). There are two methods for softening water:

Ion exchange, in which water is filtered through a column of clay minerals or synthetic polymer resin that absorb specific ions (sodium). As the water passes through the column, calcium and magnesium from the water bond to the resin and are replaced by sodium from the column. Ion exchange resins are highly specific and must be “regenerated” (Tímár-Balázsy and Eastop 1998).

Chemical agents (sodium carbonate or trisodium phosphate) that form non-water-soluble compounds with calcium or magnesium. Sequestering (chelating) agents that form water-soluble complex salts may also be used to soften water (Tímár-Balázsy and Eastop 1998).

Deionized water has had all ions (charged non-organic particles) removed. This can be accomplished by sending water through either ion exchange resins or with a reverse osmosis process using an osmotic membrane. Demineralized water has had only the cations removed (Tímár-Balázsy and Eastop 1998). The deionization process does not remove microbes or organic components; an activated carbon filtration system may be used in conjunction with the deionization process to remove organic contaminants. Deionized water will initially have a neutral pH, but will become slightly acidic (pH 5.5) upon exposure to atmospheric carbon dioxide. See also BPG Washing and Deionized water.

Distilled water is produced when water is boiled to create steam, which is then condensed and collected. Contaminants including cations, anions, metals and microorganisms are removed during this process resulting in highly purified water that acts as an aggressive solvent (Tímár-Balázsy and Eastop 1998). Water may be double or triple distilled to ensure purity. Freshly distilled water has a neutral pH that quickly becomes acidic as it dissolves atmospheric acidic gasses like carbon dioxide. Consequently, distilled water should be kept in a closed container and pH monitored during use. Distilled water may also include volatile organics. The distillation process requires significant energy and time. See also BPG Washing and distilled water.

Water Conductivity

Conductivity is the ability of a material to conduct an electric current. The greater the ion content of a solution, the higher the conductivity. Aqueous cleaning relies on ion exchange via the breaking of bonds between dirt and textile. Maintaining consistent conductivity throughout an aqueous treatment can be challenging as additives like surfactants, chelators and buffers impact ion content and ions are released from the object.  

Hypotonic solutions have a lower ion content than the substrate or object to be cleaned, which will cause the object to gain water and swell as a result of osmosis. Ions will be removed from the object through osmotic pressure. Promoting swelling of textile fibers assists with releasing soiling during aqueous cleaning.

Isotonic solutions have the same ion content as the substrate or object, which will cause minimal swelling. Isotonic solutions do not promote ion exchange, which limits cleaning efficacy.

Hypertonic solutions have a higher ion content than the substrate or object, which will cause the object to lose water and shrink through osmosis. Ions will move into the object from the solution.

Measuring Surface pH and Conductivity Using Water Drop and Agarose Plug Methods

Surfactants

The two major classes of synthetic surface-active agents (surfactants) used in textile conservation are either anionic or non-ionic. There are a number of factors that contribute to surfactant choice, anionics work best in the presence of weak bases at pH values between 7 and 8.5 , which suits cellulosic fibers but not silk and wool, which are susceptible to degradation at higher pH value. For wool and silk, conservators are more likely to choose non-ionic surfactants, as they work best in slightly acidic conditions of approximately pH 4.5 - 5.5. Until banned in the EU in 2000 due to environmental issues about its biodegradability, the non-ionic Synpernonic® N (nonylphenol ethoxylate) was typically used, and after the ban John Fields et al. conducted extensive experiments to find a suitable replacement surfactant. Fields et al. with the collaboration of Frances Hartog, a Senior Textile Conservator at London's Victoria & Albert Museum (V&A) concluded that the non-ionic Dehyphon® LS54 (LS54) - a fatty alcohol C12-14 with 5 moles of ethylene oxide and 4 moles of propylene oxide and whose cloud point of 30°C - was the most promising alternative.

The critical micelle concentration (CMC) of a surfactant is used to calculate its concentration in a wash bath. In water, the surfactant's dual amphiphilic character helps to form micelles with increasing concentration. The concentration at which micelles form is called CMC. Above the given CMC, the surfactant's surface tension no longer decreases even with the addition of further surfactant, and textile conservators usually use a detergent at a concentration of between two and five times the CMC in practice in order to wash efficiently and also to rinse successfully.

• Anionic, non-ionic, zwitterionic
• Bath pHs typical for each
• pH at which each is effective
• Effect of temperature, cloud point
• Effect of CMC (critical micelle concentration)

Bath additives

Chelators

Chelators, or sequestering agents, form water-soluble complexes with otherwise insoluble metal ions. They must ionize to sequester metal ions. The degree of ionization depends on the pH of the solution, which must be monitored and controlled throughout treatment . Chelators may disrupt mordented dyes, resulting in dye bleed or color change. See also BPG Chelating Agents

Chelators Commonly Used in Textile Conservation

• Citric Acid can be an effective chelator for some metal ions.
• Trisodium citrate can be an effective chelator for some metal ions.
• Disodium EDTA (ethylene diamine tetraacetic acid) is a strong chelator for many divalent and trivalent metal ions including calcium, copper, and iron (Sahmel et al 2012).
• DTPA (diethylene triamine pentaacetic acid) is a strong chelator for many metal ions.
• HBED (hydroxybenzyl ethylenediamine diacetic acid) is a very strong chelator for iron III. It shifts to a deep pink color when in contact with iron, this coloration reportedly remains water soluble and can be rinsed away after the cheating solution or poultice has been removed (Glenn et al 2015).  

Soil re-deposition inhibitors (some overlap with chelation)

• Sodium carboxymethyl cellulose (SCMC) may be added as a soil suspension aid to limit redisposition of soiling during the wet cleaning process. Tímár-Balázsy and Eastop recommend using SCMC in a concentration that is 0.01% of that of the quantity of surfactant (2005, 206).

Rinsing

• Water type, volume, number of changes
• Adjusting pH
  • as part of cleaning
  • to address dye changes or reverse other effects

Agitation

Sponges

A pink cellulose sponge is compressed on the surface of a whitework textile in a shallow wash bath, resulting in surfactant foam. Image credit: Jason Copes, The Colonial Williamsburg Foundation.

Sponges are an excellent tool for the application of surfactant solutions and facilitate the mechanical action that is necessary for surfactant efficacy by moving wash solutions through the object. Sponges may be used in aqueous cleaning by supporting the object on the bottom of the wash tank or other flat surface, placing the sponge flat on the surface of the object, pressing down with the palm of the hand, and releasing. The sponge will expand, pulling the washing solution up through the object as it does. When the sponge has fully expanded, it can be picked up, placed back down on the object immediately adjacent or slightly overlapping with the previous location of the sponge, and the process repeated.

This mechanical action greatly increases the efficacy of cleaning solutions, while putting little stress on the object. Dragging or dabbing the sponge on the object surface may cause damage. Net can be placed over the surface of fragile objects to protect them during sponging, and removed before rinsing (net retains surfactant and inhibits rinsing).  

There are many types of sponges available for aqueous cleaning:

Cellulose sponges are hydrophilic and therefore hold water well, but they are very heavy when wet. Colorful sponges can be useful for keeping various wash solutions separate (for example, blue for water-only sponges and pink for surfactant sponges) but the colorants in the sponges may leach. Thorough testing, soaking, and/or washing is required for new sponges.

Ramer (PVA) sponges are hydrophilic and have small holes when compared to other sponge types, making them effective at producing foam. They remain lightweight when wet and have excellent shape regain when compressed. New sponges must be soaked overnight and washed in hot water prior to use to remove the added biocide.  

Natural sponges can be useful for very fragile or delicate objects. They have large hole sizes when compared to other sponges, resulting in gentler movement of water and cleaning solutions through a textile when the sponges are compressed. They also take longer to regain their shape and volume when compressed. Natural sponges may produce less foam due to their larger hole size, which can help facilitate rinsing.

Polyurethane foam sponges effectively produce foam but do not hold water well due to their hydrophobic nature.

Sponges may be cut down if needed to better fit the palm of the hand or to better suit small objects, but cutting sponges may result in sponge “crumbs” that could be transferred to the object. Soaking or washing sponges after cutting but prior to use can reduce this risk.

Blotting

See Drying, Blotting, and Blocking.

Drying

See Drying, Blotting, and Blocking.

Special methods

Vacuum Suction Table

A suction table, or suction platen, pulls air down through the table surface, which is a perforated metal screen. Suction tables can be used in conservation for both wet cleaning and drying of objects. While a suction table may have a large working surface, it is important to mask out much of that surface to help target the suction to the area where it is needed.

• Benefits of using a suction table:
  • Moisture is pulled directly through an object with less chance of spreading beyond the area being treated
  • Greater amounts of water or cleaning agents may be introduced than in other methods of direct application
  • Cleaning agents can be introduced and rinsed from an object very quickly, limiting the time they are in contact with the object
  • Treatment can be very highly targeted by masking out a small aperture on the surface of the suction table which is useful for spot treatments where immersive wet cleaning is not an option
  • For objects that have been immersed or otherwise wetted, a suction table can be used to dry them quickly and can allow for realigning or smoothing of distortions
• Drawbacks of using a suction table:
  • Suction can be too aggressive for fragile objects
  • Water and other cleaning agents may be pulled through an object too quickly, not allowing them the contact time needed to be effective
  • Although suction helps pull moisture through an object, it can take significant trial and error to adequately control moisture and keep it from wicking and spreading to areas where it is not wanted

The process for using a suction table or platen:

• Locate a polyethylene sheet large enough to cover the entire surface of the table
• Determine the best location for a working area on the suction table surface and then cut out an aperture (roughly 1-2 inches square) in the polyethylene sheet in that location (this will be area where suction will actively be working)
  • Placing blue tape around the edges of the aperture can make it easier to see
  • Disclaimer: Although it seems logical that the smaller the aperture in the polyethylene, the more intense the suction pressure becomes, this is not necessarily the case; through significant testing, it was determined that an aperture smaller than approximately 2 inches by 2 inches cause the power of the suction to decrease

• Place blotter (if using) over the aperture
  • Thin blotter paper can be useful to get a sense of whether treatment is resulting in any movement of staining or discoloration
  • If the blotter is too thick, it will inhibit suction

• Place the object on a sling of Reemay or Hollytex
  • Having a sling larger than the object will allow for easier and safer handling of the object throughout this process

• Place the object and its sling on the suction table, aligning the area to be treated with the aperture in the polyethylene
• Only turn on the suction table once the object is in place

Methods for controlling moisture on a suction table:

• Moisture can be introduced with a dropper directly to the area of the object located over the aperture in the polyethylene sheet
  • Suction should be strong enough to pull it directly through without allowing it to bead up or spread
  • The size of the aperture plays a role in this

• To target specific areas of an object more closely, Mylar or polyethylene scraps can be cut to mask out specific shapes
• Place polyethylene or Mylar mask over the top of the object
  • When suction is on, this mask should be pulled tight against the object, sandwiching it with the table surface
• With suction on, introducing moisture with a dropper at the edge of a mask on top of the object allows it to be pulled back through the object away from the Mylar or polyethylene mask. This is useful when dealing with a tideline as it limits its ability to spread further out (This method requires significant testing to ensure that moisture is being controlled – adequate suction will limit chance of spreading)

Materials:

• Polyethylene sheet large enough to cover the suction table or platen surface
• Smaller pieces of polyethylene or Mylar
• Reemay or Hollytex larger than the object
• Thin blotter paper

Further Reading

General Resources

Textile Specialty Group.1995. Textile Specialty Group Postprints, AIC (Washington, DC). Volume 5. [Reports from a meeting entirely devoted to wet cleaning.]

Textile Specialty Group Postprints Subject Index: Aqueous Cleaning

Tímár-Balázsy, Ágnes and Dinah Eastop. 1998. Chemical Principles of Textile Conservation. Oxford, England: Butterworth Heinemann.

Space and Equipment

The following is a list of published references to wash table and other wet-cleaning equipment, in chronological order. Publications that include sketches, photographs, or other illustrations are in boldface

Landi, S. 1966. Three Examples of Textile Conservation at the Victoria and Albert. Studies in Conservation 11 (3): 143-155. Also excerpted in Brooks, M.M. and D.D. Eastop, Eds. 2011. Changing Views of Textile Conservation, Getty Publications, Los Angeles, pp153- 158. [Includes a description of a movable stainless steel washing table.]

Using a wet/dry vacuum for aqueous carpet cleaning

Columbus, J.V. 1973. Tapestry Restoration in the National Gallery. Journal of the American Institute for Conservation 13 (2):65-76. [Includes a description of the structure and use of a 14’x14’x6” bath used for tapestry cleaning.]

Finch, K. and G Putnam. 1977. Caring for Textiles. Barrie and Jenkins, London, p49. [Brief discussion of washing vessels, including floor-level temporary wash tanks. Diagram.]

Little, S. 1982. A Flexible Strainer for Wet-Cleaning, Centre de Conservation du Quebec Textile Conservation Newsletter 4: 9

Logan, J.A. 1982. Red Bay 1982-Textile Discovery. Textile Conservation Newsletter 4:4 [Field lab washing of archeological textiles]

Wilson, C. 1983. Laboratory Facilities. Textile Conservation Newsletter 4:2 [Modification of a washing tank at the British Columbia Provincial Museum. Diagram.]

Segal, M. 1985. Photographic Print Washers. Textile Conservation Newsletter 8:19. [Describes modification and use in cleaning archeological textiles. Diagrams.]

Feniak, C. and L Thivierge. 1986. PARKS CANADA Textile Conservation Section. Textile Conservation Newsletter 11:15 [Stainless steel washing table.]

Niinimaa, G. 1987. GLENBOW MUSEUM Textile Conservation Lab. Textile Conservation Newsletter 12:07 [New stainless steel washing sink with two sections. Diagram.]

Ewer, P. 1989. Tapestry Conservation Project - Biltmore house. Textile Conservation Newsletter 16:11 [Wet cleaning room for tapestry; tank with bridge.]

Niinimaa, S.G. 1995. A Private Textile Conservator. Textile Conservation Newsletter 28:35 [Establishing a textile conservation lab at home, including building a large wash table.]

Varnell, C.L. 1995. From Tubs to Tables: A Survey of Wet Cleaning Equipment Used in Textile Conservation. Textile Specialty Group Postprints, AIC (Washington, DC). 5:53. [Key features and historical examples. Photographs.]

Keyserlingk, E. and J. Vuori. 1995. Wet Cleaning of an Oversized Textile on a Vacuum Wash Table: A Treatment Phase of the Gondar Hanging at the Canadian Conservation Institute. Textile Specialty Group Postprints, AIC (Washington, DC). 5:79. [Design and use of a large shallow vacuum table. Diagram and photographs.]

Karsten, I.F. 1996. Laboratory Gadgets. Textile Conservation Newsletter 31:16 [An improved screen for wet cleaning. Diagram and photo.]

Canadian Conservation Institute. 1997. New Product: Mini Suction Table. Textile Conservation Newsletter 32:32 [Description and photograph.]

Landi, S. 1998. Practical Advice for Wet Cleaning. The Textile Conservator’s Manual. Butterworth Heinemann, Oxford, pp82-90. Also case studies on pp280-283 and 290-292. [Discusses washing on flat surfaces, in wash tanks, and outdoors in temporary washing and drying facilities. Case studies of washing a very large carpet and a tent. Many photographs and diagrams.]

Haldane, E. 1999. So that's why Textile Conservation has such a Big Studio! - Tapestry Washing at the V&A. Conservation Journal. Issue 32 (online). http://www.vam.ac.uk/content/journals/conservation-journal/issue-32/so-thats-why-textile-conservation-has-such-a-big-studio!-tapesty-washing-at-the-v-and-a/ [Description of a large tapestry wash facility. Photographs.]

Varga, L.M. 2007. A Hand-Held Surface Suction Device: Design, Construction and Application. Textile Specialty Group Postprints, AIC (Washington, DC). 17:93. [Demonstrates function on paper works of art. Diagram and photographs.]

Frisina, A. 2017. Steam Jennies, Long Arms, and Battle Flags: Textile Conservator Tom Welter's Innovative Flag Conservation Equipment (poster). Textile Specialty Group Postprints, AIC (Washington, DC). 27:261. [Poster with photographs.] https://schd.ws/hosted_files/aics45thannualmeeting2017/96/AIC2017_Frisina_Poster.pdf

Cruise, J.L. 2019. An Inexpensive, Dis-Assemblable Wash Table for the Small Textile Lab. Textile Specialty Group Postprints, AIC (Washington, DC). 29:229. [Materials, construction, and photos.]

Surfactants

Sato M., Quye A. 2019. Detergency evaluation of non-ionic surfactant Dehypon® LS54 for textile conservation wet cleaning. In: Journal of the Institute of Conservation, Volume 42, Number 1.

Hofenk De Graaff, Judith H. 2011. Some Recent Developments in the Cleaning of Ancient Textile (1982). In: Changing Views of Textile Conservation, edited by Brooks M.M., Eastop D.D., The Getty Conservation Institute, Los Angeles.

Field J., Wingham A., Hartog F., Daniels V. 2011. Surfactants Investigations into Alternatives for Synperonic N (2001). In: Changing Views of Textile Conservation, edited by Brooks M.M., Eastop D.D., The Getty Conservation Institute, Los Angeles.

Balázsy T. A., Drying Behaviour of Fibres (1999). In: Changing Views of Textile Conservation, edited by Brooks M.M., Eastop D.D., The Getty Conservation Institute, Los Angeles 2011.

Chelators

Adler, Susan and Linda Eaton. 1995. “Chelating agents in wet cleaning systems”. In Textile Specialty Group Postprints. American Institute for Conservation 23rd Annual Meeting, St. Paul. Washington, DC: AIC. 69-78.

The Dow Chemical Company. 2021. General Concepts of the Chemistry of Chelation. Technical leaflet. Accessed October 13, 2022.

Glenn, Sara, Joanne Hackett, Elizabeth-Anne Haldane and Sung Im. 2015. “Borrowing from the neighbors: using the technology of other disciplines to treat difficult textile conservation problems”. Proceeds of the Forum of the ICON Textile Group. Birbeck College, London. 33-42.  

Mina, Laura. 2020. “Foxy underpants: or the use of chelators and enzymes to reduce foxing stains on early nineteenth century men’s linen underpants”. Journal of the American Institute for Conservation 59 (1): 3-17. http://doi.org/10.1080/01971360.2019.1674604.

Sahmel, Katherine, Laura Mina, Ken Sutherland and Nobuko Shibayama. 2012. “Removing dye bleed from a sampler: new methods for an old problem”.  In Textile Specialty Group Postprints. American Institute for Conservation 40th Annual Meeting, Albuquerque. Washington, DC: AIC.78-90.

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