Safe and Harmful Materials for Use in Exhibits
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The stability of materials used in close proximity to collection objects, including the materials used to build exhibit cases, is an important conservation consideration.
Are some construction materials safer to use in close proximity to museum collections?
Research and experience has shown that some materials are more acceptable for use in close proximity to museum collections. These materials are non-acidic, non-outgassing, and chemically and physically stable. The first chart in this TechNote lists materials implicated in the unnecessary deterioration of museum collections, and the second list suggests those considered to be more acceptable.
|Materials To Avoid||Pollutants|
• sweet chestnut
• Douglas fir
• yellow pine
• red mahogany (Khaya)
• western red cedar
|acetic and formic acids; organic peroxides|
• chip board
• particle board
• interior plywoods bonded with urea formaldehyde
• C grade plywoods
|formic acid from adhesives; acetic and formic acids and peroxides from wood|
• Unrefined wood pulp papers and cardboards
|organic acids, peroxide, sulfur|
• polyvinyl chloride
• polyvinylidene chloride
• bubble wrap
• cellulose nitrate
• cellulose acetate , cellulose diacetate, cellulose triacetate (most stable in group)
hydrogen chloride and plasticizers
hydrogen chloride and plasticizers
polyvinyl chloride used in adhesive
variable–acetate group can evolve acetic acid
|Rubber (vulcanized natural or synthetic)||sulfur|
• low molecular weight polymer sponges
• polyesters (generic term; variable; may be under-cured)
|organic acids; acetates|
|fatty acids, sulfur, hydrogen peroxide, aldehydes, fatty acids, sulfur |
ammonia, fatty acids, sulfur, hydrogen sulfide
|Waxes and Plasticine||fatty acids, sulfur|
• oil based
|variable, formic acid, organic acids, fatty acids|
• protein-based glues (animal)
• rubber-based or plasterized
• cellulose nitrate
• polyvinyl acetates (especially low molecular weight)
• urea formaldehyde adhesives
• wool, animal fur, semi-tanned skins and leather
• nylon 6 and nylon 66
• permanent press and crease -resistant fabrics
• flame-resistant fabrics
• pest proofing
• fabric's dyed with sulfur dyes
Materials shown to be more appropriate for use in exhibits
Selection of exhibit construction and finishing materials should be drawn from the following list which is taken from the current conservation literature.
- Well seasoned, air-dried spruce, mahogany, walnut, basswood, poplar, balsa
- Exterior grade plywood bonded with phenol formaldehyde or non-formaldehyde emittin glue
- High-density or medium-density boards using formaldehyde-free adhesive; e.g., Resincore I Medite II Medex
Paints (require aeration/thorough curing and isolation from direct contact with display objects)
- Acrylic latex: test each brand and color before use; aerate cases at least three to four weeks before object installation
- Shellac: aerate case at least two to three weeks before object installation
- Two-part epoxy resins; 100% solid precisely mixed
- Polyacrylonites: e.g., Plexiglas, Lucite
- Polyethylene: non-chemically polymerized Polypropylene
- Polystyrenes: variable
- Polyester: variable- e.g., Mylar D which is polyethylene terephthalate
- PTEF tape
- Polyethylene: e.g., Volara type A; gas expanded foams such as Plastazote
Adhesives (require aeration/thorough curing)
- Acrylic polymer solutions (e.g., Acryloid B-72)
- Wheat starch pastes
- Methyl cellulose
- Polyvinyl acetate emulsions, neutral pH adhesive; may evolve acetates and acidic acids— aerate case thoroughly before object installation
- Double sided archival tape; e.g. 3M 415
- Hot-melt adhesives: e.g., Thermogrip 6330, Evo-Stik 7702
Caulking (requires aeration/thorough curing)
- Silicon-based sealants without ammonia, such as RTV (Room Temperature Vulcanized)
Mechanical fastening methods
- stainless steel or monel alloy staples and pins; sleeve pin mounts with inert tubing
- Vegetable fiber cloths: cotton, linen; wash with hot water before use
- Acid-free pH unbuffered (neutral) paper products (for use with photographs and protein-based materials such as silk, wool, semi-tanned skins, leathers)
- Acid-free buffered (alkaline reserve) papers (for most other materials)
Mention of a product, manufacturer, or supplier by name in this publication is for information only and does not constitute an endorsement of that product or supplier by the National Park Service. Listed materials have been used successfully in past applications. It is suggested that readers also seek alternate product and vendor information to assess the full range of available supplies and equipment.
Additional References on the Subject
Arni, P.G., G.C.Cochrane and J.D. Gray. "The emission of corrosive vapors by wood".
- I. “Survey of the acid-release properties of certain freshly felled hardwoods and soft woods.” Journal of Applied Chemistry, l5 (l965): 305-3l3.
- II. “The analysis of the vapors emitted by certain freshly felled hardwoods and softwoods by gas chromatography and spectrophotometry” Journal of Applied Chemistry, l5 (l965): 463-468.
Blackshaw, S.M. and V.D. Daniels. "The Testing of Materials for Use in Storage and Display in Museums." The Conservator, 23 (l979): l6-19.
Brady, George S. and Henry R. Clauser. Materials Handbook. 12th Edition.New York: McGraw-Hill Book Co., (1986).
Carpenter, J.M. and P.B. Hatchfield. Formaldehyde: How Great is the Danger to Museum Collections? Center for Conservation and Technical Studies, Harvard University Art Museums, Cambridge, MA. (l985).
Craddock, A.D. "Plywood as a Storage and Display Case Material." Textile Treatments Revisited. Harpers Ferry Regional Textile Group Preprints, Washington, DC (l986): 40-46.
Fitzhugh, E.W. and R.J. Gettens. "Calclacite and Other Efflorescent Salts on Objects Stored in Wooden Museum Cases." Science and Technology, R.H. Brill, Ed. MIT Press, Cambridge, MA. (l97l): 9l-102.
Hawley, Gessener G. The Condensed Chemical Dictionary. 10th Edition. New York: Van Nostrand Reinhold Co., 1981
Hodges, Henry. "Show Cases Made of Chemically Unstable Materials." Museum. 34: l (1982): 56-57.
Hopwood, Walter, R. "Choosing Materials for Prolonged Proximity to Museum Objects." AIC Preprints Seventh Annual Meeting, Toronto, Canada (l979): 44-49.
Leveque, M.A. "The problem of formaldehyde - a case study." AIC Preprints Fourteenth Annual Meeting, Chicago, IL. (l986): 56-65.
Miles, Catherine. "Wood Coatings for Display and Storage Cases." Studies in Conservation, 31 (1986): ll4-l24.
Oddy, W.A. "An Unsuspected Danger in Display." Museum Journal, 1 (1973): 27-28.
Padfield, D.E. and W. Hopwood. "Trouble in Store." Science and Technology in the Service of Conservation. IIC Congress, Washington DC (l982): 24-27.
Tennant, Norman H. and Thomas Baird. "The Deterioration of Mollusca Collections: Identification of Shell Efflorescence." Studies In Conservation, 30 (1985): 73-85.