TSG Chapter VIII. Storage of Textiles: Issues and Methods Textile Conservators Face when Planning for Textile Storage - Section B. Storage Furniture

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Contributors: Originally drafted by Dorothy Alig, Theresa Heard, and Gwen Spicer. Contributions from: Susan Adler, Deborah Bede, Alicia Bjornson, Canadian Conservation Institute, Lucy Commoner, Judith Eisenberg, Patricia Ewer, Lorna Filippini, Joy Gardiner, Martha Grimm, Robin Hanson, Susan Heald, T. Rose Holdcraft, Jane Hutchins, Claudia P. Iannuccilli, Marlene Jaffe, Mary Kaldany, Kennis Kirby, Teresa Knutson, Susan Mathisen, Zoe Annis Perkins, Betty Seifert, Textile Conservation Laboratory, and R. Scott Williams
Editors: Kathy Francis, Jane Lynn Merritt, Nancy Pollak, and Deborah Lee Trupin. Final Revision, April 2, 1998.
Copy Editor/Layout Consultant: Jessica S. Brown

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Copyright: 2018. The Textile Wiki pages are a publication of the Textile Specialty Group of the American Institute for Conservation of Historic and Artistic Works.
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Storage Furniture

Purpose

Well-designed storage furniture, also referred to as storage units or storage cabinets, provides a protected environment for collections. Storage furniture can offer both physical and environmental protection.

Factors to Consider

Factors to consider include the type of collections to be housed in the units, the design of the units, the materials from which the units are constructed, and the funds available.

Design of Units

  • Storage units should be movable or be accessible to art transport equipment (carts, dollies, forklifts, etc.).
  • If movable, or compactor, units are chosen, the effects of movement and vibration on the stored collections should be considered.
  • Bases of storage units should be elevated as a precaution against water damage.
  • Tops of units should not be used as a shelf because they leave artifacts and artifact containers unprotected.
  • Doors, blinds, curtains, etc. on the storage units are recommended to control dust and light exposure.
  • The degree of air circulation desired and whether or not this needs to be regulated must also be considered.
- Increased air circulation (meaning clean air exchanges) serves to dilute volatile compounds emitted from materials in the storage units.
- Air circulation makes the storage units less attractive to vermin.
- It is important to consider the overall air quality in the building when deciding on the amount of air circulation desired.
- There is some evidence that less air circulation is connected with less damage from oxidation.
  • The storage units can be fitted with drawers, shelves, or trays according to the needs of the collections.
  • Adjustable storage space as opposed to fixed shelf, drawer, or suspension spaces will accommodate shifts in collecting directions.
  • An assessment of the size and type of objects in the collection and their use (permanent storage, rotating exhibits, etc.) will indicate the types of storage needed.
  • Consideration of types, sizes, and conditions of objects in conjunction with space and staff availability will determine unit sizes.

Materials for Construction of Cabinetry

Wood Products

PROS:
  • Historically, wood products are the most common material.
  • Wood products are relatively low-cost, easy-to-use, and easily available.
  • The hygroscopic character of wood creates a buffering effect against rapid change of relative humidity. Once wood products are sealed as recommended, however, their buffering effect is reduced.
CONS:
  • Many wood products contain volatile components, including formaldehyde, which may damage artifacts especially at higher RH levels.
  • It may not be possible to determine the exact wood species in a given product.
  • Wood always releases acid (albeit at a decreasing rate).
- Therefore wood causes acid damage to materials stored in direct contact with it.
- Inside a closed wood case the concentration of acids increases with time, but at a gradually decreasing rate.
  • Some storage materials break down more readily when in contact with wood.
  • The adhesives used in the formation of wood products need to be identified and assessed for stability.
Some wood products produce lower emissions than others. Among these are:
  • Solid wood. Low acid emitting woods include: mahogany, walnut, spruce, poplar, balsa, and American beech. (This is a partial list; refer to Tétreault, 1992a .)
  • Plywood with each outside layer (veneer or ply) of low acid emitting woods. However, the adhesive used to assemble the plywood must also be evaluated, avoiding urea-formaldehydes.
  • Wood products containing phenol-formaldehyde or formaldehyde-free adhesives (Exterior and Exposure 1 type plywood with waterproof glue, or formaldehyde-free Exterior type Medium Density Fiberboard, such as Medex®).
Severe emissions are caused by:
  • Adhesives and additives commonly found in the wood products, such as urea-formaldehydes.
  • Species such as new oak, teak, Douglas fir, red cedar, and chestnut. (Refer to Tétreault, 1992a, op. cit.)
Options
  • Substitutes for wood can be metal with powder coating, galvanized or stainless steel, aluminum, acrylic, or glass. (See also below Thermosetting Powdered Coatings)
  • Stored collections can be protected from storage units made of wood and wood products by the use of surface treatments that create physical or chemical (i.e., sealants or coatings) barriers. However, all artifacts need to be isolated even from sealed surfaces.

Coatings (or Sealants) on Wood

PROS:
  • Coatings help to reduce volatile emissions.
  • Sealants are easy to apply and can be purchased from local stores.
CONS
  • The efficacy of each product as a barrier varies from product to product and is highly dependent on proper application of the coating.
  • The coatings may also release organic acids, peroxides, and formaldehyde, all at different rates.
  • Cracks or punctures may leave openings for off-gassing.
  • Formulations change without notice.
  • The long-term stability of all coatings is in question.
Sealants that are acceptable:
  • Shellac is relatively inert, once the solvent has evaporated, but note that shellac is a less effective barrier than other acceptable sealants.
  • Air-drying lacquers are relatively inert, once the solvent has evaporated.
  • Acrylic latex paints and varnishes or the lower-solvent formula modified acrylic latex paints and varnishes.
  • Moisture-cured polyurethane varnish (urethanes that cure or polymerize by reaction with atmospheric water vapor).
  • Unpigmented waterborne acrylic urethane varnish.
  • Moisture-cured urethanes (ASTM Type 2, one-package moisture-cured urethanes) have shown promise as noncorrosive coatings (Miles 1986).
  • Vapor barrier paint composed of butadiene-styrene.
  • Aluminum flake paint on an acrylic resin base (Krylon®).
Sealers that are not acceptable:
  • Any oil-based sealer.
  • Any lead-based sealer.
  • Alkyd resin.
  • Oil-modified polyurethane (ASTM Type 1, one-package prereacted urethanes).
  • Nitrocellulose lacquers.
  • One-part epoxies.
  • Products treated with fire retardants should be avoided.
  • Corrosion-resistant paints.
Other factors to consider:
  • All coatings should be applied in at least two layers.
  • No applied coating is a perfect barrier. However, each additional layer increases its performance as a vapor barrier. For added protection, cover a sealed wooden surface with a physical barrier.
  • Any coating applied to wood should dry (and off-gas) for at least one month in a well-ventilated area before use.
  • There is no conclusive data on the behavior of coatings as they age, thus there is no conclusive data on the lifespan of coatings.
  • To reduce build-up of volatile components, ventilation holes can be cut into cabinets to allow air circulation. Holes should be fitted with filters to protect contents against particulate soils.

Physical Barriers on Wood

Considerations for choosing physical barriers include durability, cost, quality of construction, and the adhesives used. Care is needed when choosing adhesives. (See Tables 1 and 2.)
Studies done at the National Museums of Scotland have shown that physical barriers, properly applied, were more effective against migrating gases than were the sealants tested (Eremin and Wilther1997).
PROS:
  • Barriers cover acidic wooden surfaces, reducing the rate of emission of migrating compounds.
  • Barriers are easy to apply.
CONS:
  • Pin holes in barriers can easily occur, undermining the objective.
  • The barrier only reduces the rate at which the compounds can migrate and will need to be changed. The frequency of change is determined by the barrier used.
  • Any uncoated surfaces, such as the bottoms of shelves, and improperly joined seams will still emit volatile gases.
Physical barriers that are acceptable:
  • Aluminized polyethylene or polyester barrier film (such as aluminized Mylar® or Marvelseal®).
- The polyethylene film barriers can be attached to the construction material with heat from a hot iron or hot air gun. The plastic melts and acts as an adhesive.
- Stainless steel staples can also be used. The holes from staples need to be sealed with aluminum tape. Staples can be harmful if in contact with artifacts.
  • Acid-free papers, boards, and folder stock. Papers can scavenge gasses passing through (from the wood). At some point the scavenging sites in the paper become used up, so the paper no longer will have the scavenging or barrier properties. These barriers can be attached with synthetic wallpaper paste or archival-quality double-sided tape (e.g., 3M #415®).
  • High pressure decorative laminates (also called decorative laminates): laminates of melamine or phenol-formaldehyde (e.g., Formica®). However the adhesives used to secure the laminate to the wood should be chosen with care to avoid adhesives that will out-gas formaldehyde.
  • Polyester film (Mylar®) or Flexcon®, an acrylic adhesive-backed polyester film. N.B.: This is not as complete a barrier as the aluminized film. The smaller the mil (thickness), the less effective the barrier.
Physical barriers that are not acceptable:
  • Cardboard or any other non-archival-quality board.
  • Newsprint or any other non-archival-quality paper.
  • Non-archival-quality plastic sheeting.

Metal Products

PROS:
  • A metal product, properly coated, is inactive and does not emit volatile gases.
CONS:
  • Metal does not buffer changes in temperature and relative humidity.
  • There is potential for corrosion and condensation.
  • The furniture and components may be heavy and expensive.
  • Areas with flaked paint or scratches may rust.
Acceptable metal products:
  • Steel, if properly coated. (See below.)
  • Aluminum: lightweight; inert oxide coating forms on surface.
  • Chrome-plated metal, such as wire racks.

Coatings on Metal Substrates

Liquid and baked
  • The resin types are oil-modified alkyd, two part epoxy, nitrocellulose, and urea, or mixtures of these.
  • Method of application - Applied with solvents and baked at temperatures that depend on the type of resin, but usually in excess of 325°F (163°C) for 20 minutes.
PROS:
  • Benefit of liquid and baked coatings is ease of application (for the manufacturer). Thus the furniture is generally less expensive than powdered resin coated metal furniture.
CONS:
  • Incomplete curing means the product is not fully cross-linked and results in substantial out-gassing of xylene and toluene. Monomers or low molecular weight products could also result and off-gas.
Thermosetting Powdered Coatings
  • The most commonly used thermosetting powders are resins based on epoxy, polyester, polyurethane, and acrylic resin systems. Each resin has its own properties. Manufacturers appear to use different ones, in combination with different pigments. Currently, powder coating is seen as the best coating for steel cabinets or shelving.
  • Method of application - The resin is electrostatically applied in powder form onto the fully formed cabinet. The cabinet is baked at 375–400°F (190.5-204°C) for 20–30 minutes. The exact temperature and bake time is determined by the choice of color.
PROS:
  • There is no solvent vehicle, eliminating the potential of solvent off-gassing.
  • CCI (Boyle 1988) tested some cured powder coatings based on polyester-TGIC (triglycidyl isocyanurate), epoxy, polyurethane, polyester, polyester/urethane hybrid, and Teflon resins and found these to be acceptable in terms of off-gassing and chemical stability. A powder coating based on nylon was thought to be less suitable because the method of application of molten nylon might have induced degradation of the nylon.
CONS:
  • Powdered-resin coated shelving is more costly than other types.

Gasket Materials

Gaskets are used to help control the environment within a storage cabinet as well as to minimize entrance of airborne pollutants.

Recommended materials for gaskets:
  • Silicone is the preferred gasket material.
- Prefabricated silicone gaskets do not emit acetic acid, nor do they degrade to produce volatile degradation products.
- Silicone is available in several forms as solid or foamed sheets, extruded profiles, and tubing. Companies can custom manufacture shapes according to specifications. Not all cabinet companies install silicone and some charge extra to do so.
- Note that silicone is also used in semi-solid or paste caulks and sealants that cure or vulcanize at room temperature (RTV) by reaction with moisture in the air. Those which emit acetic acid upon reaction are unacceptable for gaskets, but those which release alcohols are acceptable.
  • EPDM (ethylene-propylene diene monomer) rubber, made without sulfur vulcanizing agents, was tested by CCI and found to be safe. (N.B.: Many of these commercial products also have rubberized adhesive tapes attached; such products cannot be used.)
  • Extruded closed-cell polyethylene foam called Backer Rod HBR, Type C.
  • Cross-linked, closed-cell polyethylene foam, such as Volara® and Plastazote®.
Materials not recommended for gaskets:
  • Chlorine-containing compounds such as PVC [poly(vinyl chloride)].
  • Chlorinated rubbers or rubbers containing sulfur vulcanizing agents.
  • Chloroprene (Neoprene®).
  • Polyester polyurethane foam (polyester foams).
  • Polyether polyurethane foam (polyurethane foam).

Materials Testing

All materials should be tested before their introduction into the collection. The quantity of volatile compounds that an artifact can withstand depends on the artifact.

  • CCI tests some products as they become available, resources permitting. Their reports are available upon request.
  • Note that a manufacturer can modify a product without notification on the product packaging.
Swab Tests (also known as Solvent Cure Test or MEK Rub Test).
Purpose - This test determines the completeness of curing of baked coatings on metal cabinetry. The procedure for doing the test and evaluating the results has been published by The Powder Coating Institute 1987, which should be consulted for specifics. The procedure is:
1)Saturate cotton swab with methyl ethyl ketone (MEK).*
2) Rub swab over surface of the coating for 30 seconds.
3) Repeat for 60 seconds.
4) Look for change in appearance to surface after each rubbing.
Corrosion coupon test, the "Oddy test"
Purpose - This test assesses the corrosive components in the proposed material by measuring the degree of corrosion on metal coupons. The coupons are sealed in a test tube with the material being tested and some moisture. The test was first described by W.A. Oddy in 1975. An improved version is detailed in Green, 1995.
  • Return policy - It is suggested that passage of appropriate tests be written into contracts for the purchase of cabinetry.


*NOTE: MEK Health and Safety Warnings: Severe fire and explosion hazard (flash point is 21°F or 6°C). Store in cool place away from ignition sources or oxidizing materials. Use under fume hood with rubber gloves and goggles.

Summary of Materials to Avoid for Storage Furniture

Table 1: Summary of Materials to Avoid for Storage Furniture
Material Volatile/Migrating Products
Adhesives
    Cellulose nitrate Nitric acid
    Epoxy Organic acids
    Polyvinyl acetates, especially low molecular weights Acetic acid
    Protein-based glues Sulfur
    Vulcanized natural or synthetic rubber Sulfur
    Chlorinated rubbers (chloroprene, Neoprene®) Hydrochloric acid
    Plasticized adhesive Plasticizers
Foams
    Low molecular weight polymer "sponges" Acetates
    Polyesters (generic term) Acetates
    Polyurethane Organic acids
    Vulcanized natural and synthetic rubber Sulfur
    Chlorinated rubbers (chloroprene, Neoprene®) Hydrochloric acid
    Poly(vinyl chloride) Hydrochloric acid, plasticizers
Paints
    Alkyd Formic acid
    Epoxy Can contain acetic acid
    Oil-based Organic acids, peroxides
    Oil-modified polyurethanes Organic acids, peroxides
Plastics
    Poly(vinylidene chloride) barrier-coated bubble wrap Hydrochloric acid
    Cellulose acetate Acetate groups can form acetic
    Cellulose diacetate acid, especially at high
    Cellulose triacetate temperature
    Cellulose nitrate Nitric acid
    Some polyester Formic acid emitted from under-cured polyester
    Poly(vinyl chloride) Hydrochloric acid, plasticizer
    Poly(vinylidene chloride) Plasticizer
Other
    Acetic acid releasing RTV silicone/caulk sealant Acetic acid
    Soft ester waxes and plasticene Fatty acids, sulfur
Woods
    Basswood
    Birch
    Cork Acetic and formic acids,
    Douglas fir Organic peroxides,
    Oak Propionic acids
    Red mahogany (Khaya)
    Sweet chestnut
    Yellow pine
Wood products
    Chip board Formaldehyde from adhesive;
    Interior plywood bonded with urea formaldehyde Acetic and formic acids and peroxides from wood
    Masonite
    Particleboard Aldehydes, acid catalysts, etc.
    Fiberboards organic acids, inorganic acids,
    Urea formaldehyde impregnated paper laminated panelboard sulfur dioxides, formaldehyde
    Unrefined wood pulp papers and cardboard
Carpets
    Rubber backings Vulcanized rubber backings produce sulfur as they degrade; accumulate dust and harbor insects


See also Storage Materials, Table 3

Summary of Materials Considered Safer for Storage Furniture

Table 2: Summary of Materials Considered Safer for Use in Storage Furniture
Adhesives
    Acrylic emulsions
    Double-coated tape (acrylic-based adhesive on polyester carrier), i.e., 3M #415®.
Foams
    Polyethylene
        normal, such as Ethafoam® or Nomaco Backer Rod HBR® Type C; or
        cross-linked, such as Plastazote® or Volara®
    Extruded plank polystyrene foam insulation, (not expanded bead polystyrene foam)
Paints/Sealants
Remember that each brand and color of any paint should be tested before use. (See Materials Testing.)
    Acrylic latex paints and varnishes or modified acrylic latex paints and varnishes
    Shellac
    Moisture-cured urethanes
    Air-drying lacquers
    Acrylic urethanes
    Vapor barrier paint composed of butadiene-styrene
    Aluminum flake paint on an acrylic resin base (Krylon®)
Woods
    Balsa
    Mahogany
    Walnut
    Spruce
    Poplar
    American beech
Wood Products
    Plywood with the outside layers of low acid-emitting woods and with the layers adhered with a phenol formaldehyde adhesive or a formaldehyde-free adhesive.
    High- and medium-density fiberboard, made from hardwoods, such as Medex®.


Note: For names and addresses of manufacturers of products cited in this section, consult Rose and de Torres 1992.
See also Storage Materials, Table 4

References

Boyle, M. 1988. EDR Report 1655, Suitability of powder coatings for use in the museum environment: Volatile release/generation over time. Canadian Conservation Institute, Ottawa, Canada, August.
Eremin, K. and P. Wilther. 1997. The Effectiveness of barrier materials in reducing emissions of organic gases from fiberboards: Results of preliminary tests. In Preprints of the ICOM Committee for Conservation 11th Triennial Meeting. London: James and James:27–35.
Green, L.R. and D. Thicket. 1995. Testing materials for use in the storage and display of antiquities - A revised methodology. Studies in conservation 40(3):145–52.
Miles, C. 1986. Wood coatings for display and storage cases. Studies in conservation 31:114–24.
Oddy, W.A. 1975. The Corrosion of metals on display. In Conservation in Archaeology and the Applied Arts: Contributions to the Stockholm Congress. London: International Institute for Conservation of Historic and Artistic Works:235–37.
Powder Coating Institute. 1987. Recommended Procedure for Solvent Cure Test. Alexandria, Va.: Powder Coating Institute, 1987.
Tétreault, J. 1992a. Matériaux de construction, matériaux de destruction [Materials of construction, materials of destruction]. In La conservation préventive. Paris:ARAAFU: 163–76.

Further Reading

American Plywood Association. 1993. Panel handbook and grade glossary. Tacoma, Wash.: American Plywood Association.
Arni, P.C., et al. 1965. The emission of corrosive vapors by wood: Parts 1 and 2. Journal of applied chemistry 15:463–68.
Beaudoin-Ross, J. and E. Burnham. 1990. Recent trends in costume and textile storage. Textile conservation newsletter supplement: Spring: 2–11.
Blackshaw, S.M. 1982. The Testing of display materials. In The Care of ethnographic material: Occasional paper no 1. D.L. Jones, ed., Ipswich, U.K.: Ipswich Museum: 40–45.
Burke, J. 1992. Vapor barrier films. WAAC Newsletter 14(2):13–17.
Burke, J. 1993. Communication with Delta Design.
Burke, J. 1993. Communication with Interior Steel.
Craddock, A.B. 1992. Construction materials for museum storage. In Conservation concerns: A guide for collectors and curators. Bachmann, K., ed. Washington, D.C.: Smithsonian Institution Press:23–28.
Craddock, A.B. 1986. Plywood as a storage and display case material. Textile treatments revisited, National Museum of American History, Smithsonian Institution, Washington, DC, November 6 and 7, 1986. Harpers Ferry Regional Textile Group Preprints. Washington, D.C.:40–45.
Druzik, C.M. and D.C. Stulik. 1991. Formaldehyde: Detection and mitigation. WAAC Newsletter 13(2): 13–16.
Druzik, J.R. 1991. An Integrated approach to reducing concentrations of indoor generated pollutants. Object Specialty Group Postprints: 42–65.
Farmer, R.H. 1962. Corrosion of metals in association with wood. Part I: Corrosion by acidic vapours from wood. Wood 27:326–28.
FitzHugh, E.W. and R.J. Gettens. 1971. Calcalacite and other efflorescent salts on objects stored in wooden museum cases. In Science and archeology. R.H. Brill, ed. Cambridge, Mass.: MIT Press:91–105.
Grassie, N. and G. Scott. 1985. Polymer degradation and stabilization. Cambridge, England: Cambridge University Press.
Hatchfield, P. and J. Carpenter. 1987. Formaldehyde: How great is the danger to museum collections? Cambridge, Mass.: Center for Conservation and Technical Studies, Harvard University Art Museum.
Hatchfield, P. and J. Carpenter. 1986. The Problem of formaldehyde in museums. The International journal of museum management and curatorship 5:183–88.
Hopwood, W.R. 1979. Choosing materials for prolonged proximity to museum objects. Preprints of the American Institute for Conservation of Historic and Artistic Works Annual Meeting, Toronto, 1979: Washington, D.C.:American Institute for Conservation of Historic and Artistic Works:44–49.
Horie, C.V. 1987. Materials for conservation. London: Butterworths.
Howie, F.M. 1992. Care and conservation of geological materials. London: Butterworths.
Lee, L.R. and Thickett, D. 1996. Selection of materials for the storage and display of museum objects. British Museum Occasional Paper 111. London:The British Museum.
Leveque, M.A. 1986. The Problems of formaldehyde: A case study. Preprints of the American Institute for Conservation of Historic and Artistic Works Annual Meeting, Chicago.
McManus, E. 1996. Some applications of laminated heat sealable films for collections storage. ICOM Ethnographic Conservation Newsletter 14:2–3.
National Institute of Standards and Technology. Voluntary product standard, PS1–83: Construction and industrial plywood. Office of Standards and Services, December 30, 1983, Revised March 1985.
Oddy, W.A. 1973. An Unexpected danger in display. Museum journal 73(1):27–38.
Padfield, T. 1982. Trouble in store. Science and technology in the service of conservation, Preprints of the International Institute for Conservation of Historic and Artistic Works Conference, Washington, 1982. London: International Institute for Conservation of Historic and Artistic Works:24–27.
Raphael, T. 1991. Conservation guidelines, design and fabrication of exhibits. Harpers Ferry, W.Va.: Division of Conservation, National Park Service.
Rose, C. and A.R.de Torres, eds. 1992. Storage of natural history collections: Ideas and practical solutions. Pittsburgh: Society for the Preservation of Natural History Collections.
Tétreault, J. 1997. Determination of concentrations of acetic acid emitted from wood coatings in enclosures. Studies in conservation 42:131–56
Tétreault, J. 1992b. Measuring the acidity of volatile products. [Translation from La mesure de l'acidité des produits volatils.] Journal of IIC-CG 17:17–25.
Tétreault, J. and E. Stamatopoulou. 1997. Determination of coatings of acetic acid emitted from wood coatings in enclosures. Studies in conservation 42: 141–56.
Textile Conservation Center. 1986. Reducing damage from wood-based storage products. Technical Bibliographies. North Andover, Mass.:Textile Conservation Center, 1986.
Thomson, G. 1986. The Museum environment, 2d ed. London: Butterworths.
Werner, G. 1987. Corrosion of metal caused by wood in closed spaces. In Recent advances in conservation and analysis of artifacts. London: Summer School Press, University of London: 185–87.
Williams, S. 1993. Plasticized PVC in museums: Don't use it. CCI Newsletter 12:4–5.
Williams, S. 1995. CCI Report No. 600: Celfort Rigid Extruded Polystyrene Foam. Ottawa: Canadian Conservation Institute.



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