PMG Section 1.5.7 Cases, Packing, and Crating Material
Photographic Materials Conservation Catalog
Exhibition Guidelines for Photographic Materials
Date: July 2004
Contributors to WIKI version: Your name could be here!
Compiler: Stephanie Watkins, 1993-2004
Initiator: Douglas Severson, 1992-1993
Contributors (Alphabetical): Catherine Ackerman, Nancy Ash, Sarah Bertalan, Jean-Louis Bigourdan, Barbara N. Brown, Ed Buffaloe, Carol Crawford, Corinne Dune, Thomas M. Edmondson, Debra Evans, Julia Fenn, Betty Fiske, Gwenola Furic, Judy Greenfield, Doris Hamburg, Marc Harnly, Pamela Hatchfield, Cathy Henderson, Nancy Heugh, Ana Hofmann, Emily Klayman Jacobson, Martin Jürgens, Nora Kennedy, Daria Keynan, Lyn Koehnline, Barbara Lemmen, Holly Maxson, Constance McCabe, John McElhone, Cecile Mear, Jennifer Jae Mentzer, Jesse Munn, Rachel Mustalish, Douglas Nishimura, Leslie Paisley, Sylvie Pénichon, Hugh Phibbs, Dr. Boris Pretzel, Dr. Chandra Reedy, Nancy Reinhold, Andrew Robb, Grant Romer, Kimberly Schenck, Douglas Severson, Tracey Shields, Angela Thompson, Sarah Wagner, Clara von Waldthausen, Dr. Mike Ware, Stephanie Watkins, Dr. Paul Whitmore, Faith Zieske, Edward Zinn.
First edition copyright: 2004. The Photographic Materials Conservation Catalog is a publication of the Photographic Materials Group of the American Institute for Conservation of Historic and Artistic Works. The Photographic Materials Conservation Catalog is published as a convenience for the members of the Photographic Materials Group. Publication does not endorse nor recommend any treatments, methods, or techniques described herein.
Cases, and Packing and Crating Materials for Photographic Materials
Considerations for display cases, packing materials, and crates
- Light intensity at the surface of the displayed item should be accurately measured and should conform to the specifications for the object. Ritzenthaler et al. (1985,127-128) warn: "Generally light sources within exhibit cases are not necessary and should be kept off, or the units should be removed entirely, since they often emit too much light and can contribute to an excessive build-up of heat. If conditions within the exhibit area require lights within cases, however, fluorescent tubes are recommended because they will not give off as much heat as incandescent bulbs. Fluorescent tubes must be covered with ultraviolet filters (or low ultraviolet emission tubes should be used). Diffusion panels also should be incorporated into the light units to ensure even illumination of the entire case and to keep anyone object from receiving too much light. Lights within cases should be on only when viewers are present. Other light sources in the exhibit gallery must be evaluated as well. Windows should be glazed with ultraviolet filtering sheets, and filters should be placed over all fluorescent tubes. Beams from spotlights or track lighting should not be aimed to fall directly on photographic images. To diminish problems posed by light within the exhibition gallery, exhibit cases can be glazed with ultraviolet filters."
- Temperature and humidity within the case should be maintained at stable and reasonable levels. "The most economical means to accomplish [recommended requirements for temperature and humidity] is to make sure the exhibition cases are placed in areas that are temperature and humidity controlled. Cases should not be airtight, but should allow for ventilation so that conditions within the cases will equal those in the exhibition hall. Filters may be placed over air holes to prevent dirt and dust from entering exhibit cases" (Ritzenthaler et al. 1985, 127). Hygroscopic lining and packing materials (e.g., paper, boards) that adsorb and desorb can buffer items against small moisture changes. Lateral case entry design is preferred over vertical (e.g., five-sided acrylic vitrine) to help maintain relative humidity (Raphael 1991).
- Materials off-gassing in microclimates (such as cases) can have a far more deleterious effect on photographic materials than overall air quality present in a building because of entrapment and buildup of pollutant gasses (Green and Thickett 1994, 4). To most effectively retard or reduce the likelihood of chemical damages, it is recommended that only the best-quality materials passing the Photographic Activity Test (P.A.T.) be used. Also, ensure that materials used in conjunction with photographs on exhibit are of good quality before all the activated-carbon filters in a case or the air handling system are changed. Fabrics woven with activated carbon can be beneficial in reducing the possible buildup of gaseous contaminants. However, charcoal cloths can contain poly (vinyl chloride) components, and direct contact with photographs should be avoided.
- All construction materials, finishes, paints, fabrics, and sealants must be non-reactive with photographs and must be fully cured (minimum three weeks) prior to use. Testing prior to use and installation is encouraged. It is a good idea to allow space between the case and wall, especially exterior walls (Raphael 1991).
- Plywood used for building exhibition spaces or for cases should be laminated with phenolformaldehyde adhesives, as these appear to be more stable than the urea-formaldehyde adhesives (Anderson 1991), or melamine formaldehyde (Glaser 1994, 4). American Plywood Association (APA) material is certified to be made with phenol-formaldehyde resins (Craddock 1992, 25). Wood comes in many grades of quality; preferred are birch plywood made with phenol-formaldehyde adhesive (exterior grade with moisture-proof adhesive), marine grade (made with moisture-proof adhesive with no interior voids), type one (strongest), AA or AB (best face quality without knots on either side) or Medex (particleboard with phenolic resin matrix). It is becoming increasingly difficult to obtain non-processed, non-laminated woods (see section 188.8.131.52.). Honduras mahogany, balsa, basswood, poplar, and Sitka spruce, with-a minimum of three coats of polyurethane, have been used in exhibition cases.
- Plastic frames and vitrines can absorb and retain pollutants from the materials stored within them. Plastic vitrines, especially "poly (carbonate) and poly (methyl methacrylate), should not be reused indiscriminately" (Fenn 1995). Therefore whenever possible, virgin plastic vitrines and frames should be used with the most reactive types of photographic materials. Plastics that are deformed, discolored, or crazed should not be used.
- Non-adhesive techniques are best for constructing cases and interior supports. Support materials such as cradles, wedges, straps, and snakes may be necessary for the safe display of albums and books with photographic material. Straps used to hold albums and books open should be made of poly (ethylene), poly (propylene), or poly (ethylene terephthalate) (MYLAR® Type 0, Melinex® 516) without additives. The thinnest and "softest" material for the support needed is best. Straps should be used with caution and away from image areas when possible, as strap edges can cause physical damage. However, set too loose, the straps may be ineffective. Explicit instructions should be given to handlers and installers using straps.
Suitable materials for constructing exhibition cases and traveling cases
The following lists are based on information in Miles (1986), Raphael (1991), Craddock (1992), Greenfield n. d. [c. a. 1992], Wilhelm (1993, 511), and Hatchfield (1996):
- Adhesives: silicone, acrylic adhesives (3M #415), poly (propylene) and poly (ethylene) hot-melt adhesives, two-part epoxy or moisture-cured poly (urethane) with several weeks of airing
- Cases, traveling: ribbed aluminum, fiberglass, or molded poly (propylene) with sturdy handles and locks
- Fabrics: unbleached, undyed, washed cottons or linens, polyester, cotton-polyester blends, fabrics without flame retardants, surface coatings such as permanent press, sizing, or dyes
- Filters (Sorbants) (Suitable for cases, but do not put these materials in direct contact with photographic materials): activated charcoal, 4% potassium permanganate on neutral activated alumina (PurafiFM), molecular sieves (zeolites), silica gel
- Gaskets: silicone, poly (tetrafluoroethylene) (Teflon™), acrylic felt
- Glazing: glass, many glass laminates, acrylic sheeting, poly (methyl methacrylate) (Plexiglas™)
- Humidity control: silica gel, dry desiccant salts
- Packing material, short-term for crates: poly (ethylene) foam (Ethafoam®, Volara®), poly (propylene), poly (butylene)
- Paints, coatings, and varnishes: acrylic paint, oven-baked enamels and lacquers, latex paints without bacteriocides, water-based aliphatic urethane (3 coats minimum), Acryloid B-48~TM, B-72™, B-67™
- Plastics and films: acrylic (Lucite™), poly (ethylene terephthalate) (Mylar Type DTM, Melinex 513™), high-density and low-density poly (ethylene) (Ethafoam™, Volara™), poly (propylene), poly (carbonate) (Lexan™), poly (styrene), poly (methyl methacrylate) (Plexiglas™), metal laminated films (Corrosion Intercept™, MarvelseaFM, aluminum poly [ethylene] nylon foil)
- Metals: anodized aluminum, anodized steel, chrome-plated steel, nickel-plated steel, powder-coated baked enamel stainless steel (when sufficiently heated and fully cured)
- Supports: Tycore™ (paper honeycomb panels), aluminum honeycomb panels, Alucobond™ (aluminum/poly (ethylene) panels)
- Wood, crates: plywood (laminated with phenol-formaldehyde or melamine formaldehyde adhesive)
The following lists of unsuitable materials are based on information in Miles (1986), Thomson (1986,156), Greenfield n. d. [c. a. 1992], and Wilhelm (1993, 511):
- Adhesives: protein-based glues, cellulose acetate resin, cellulose diacetate resin, cellulose nitrate resins and adhesives, most pressure-sensitive tapes, spray adhesives, formaldehyde-based adhesives, melamine-based adhesives, urea-based adhesives, polysulfide adhesives, poly (vinyl acetate) emulsion
- Fabrics: wool, wool felts, fire-retardant products on doth
- Gaskets: vulcanized rubber and rubber derivatives, poly (vinyl chloride), poly (urethane) foams
- Humidity control: open-pan liquid desiccant salts
- Packing material: urethane, poly (styrene), poly (vinyl chloride) foams
- Paints, coatings, and varnishes: drying oils, oil modified, and oil-based paints including alkyds and enamels (dried at normal temperatures, not oven-baked), lead based paints, one-component poly (urethane) varnishes (Varathane™) and resins, epoxy ester paints, aluminum paints, silicone paints
- Plastics and films: cellulose nitrate, poly (vinyl chloride), ultraviolet radiation absorbing surface finishes (laminates appear to be all right)
- Wood: oak (especially), yellow birch, beech, teak, plywood, particleboard, Formica®covered plywood and particle wood, Masonite®, Medite FM (urea-formaldehyde resin), and Medite IITM (formaldehyde free, has acetates), MDO (medium-density overlay) (see Framing Materials section)