PMG Section 1.5.5 Hinging and Mounting Materials

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Photographic Materials Conservation Catalog
Chapter 1 - Exhibition Guidelines for Photographic Materials

Date: July 2004
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 Jurgens, 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 Penichon, 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 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.

1.5.5 Hinging and Mounting Materials for Photographic Materials

1.5.5.1 Non-adhesive methods
Many photographic conservators are increasingly opting for non-adhesive hinging and mounting methods as more becomes known about the affects of adhesives on photographic materials. Some types of photograph and print materials, such as dye-based inkjet prints, may be sensitive to both water and solvent-based adhesives. Paper and poly (ethylene) terephthalate film, such as MYLARTM Type D corners can be used for mounting photographs. Polyester may be preferred when the mounting corners will be visible, but must be used with extreme caution, however; it can be too rigid and the edges too sharp, thereby causing physical damage to the photograph. Sharp edges may be rounded with a tacking iron or heat welder. Polyester is often attached with pressure-sensitive adhesive tapes that fail under cold flow conditions (Phibbs 1994). Ritzenthaler, MunoH, and Long (1985, 128) warn "Photographs should not be flexed to position a print within the corners, since such action could break emulsions and possibly crack brittle supports. The safest approach is to attach two corners to the mount board and then to slip the photograph into place; the final two corners should be slipped onto the photograph while it is supported flat on the mount. The corners should not fit the photograph too snugly as this could cause the print to buckle. Very often three rather than four corners will suHice to hold a photograph in place. When dismantling the unit, the corners should be removed from the mount board; no attempt should be made to flex the photograph out of the corners." Be sure to document any information, signatures, or inscriptions on the back before attaching corners to avoid unnecessary un-mounting and re-mounting. Mulberry (Kozo) fiber papers can be folded to produce corners effective for holding matted photographs (Phibbs 1994). Paper corners can be held in place with various adhesives and hinging clothes or tapes. Unmounted lightweight papers, such as early albumen prints, sag when corners of any kind are used (Bertalan and Phibbs 1988). Also, the corner is the weakest part and should not be subjected to stress. Edge strip supports (channels of paper or polyester around the perimeter) can be used to "hinge" some prints. "Z" folded channel strips can be used for lightweight paper or those with designs flush with the edge (Phibbs 1994). Photographs on thick or distorted supports or mounts can be housed in a sink mat. Photographs in historic frames without matting can be separated from the glazing with spacers (See Phibbs 1994a for diagrams and instructions.).

1.5.5.2 Adhesive choices
Ideally, the use of adhesives in the hinging and mounting procedure should be minimized as much as safely possible. Natural water-based adhesives may not adhere to modern support materials, causing physical damage when the adhesive fails. Wheat starch paste has been used "dryly" to hinge paper-based photographs when moisture is not a problem for the image or support and dextrin has been used with plastic-based supports. Using desiccated blotters (blotters placed on a warm hot plate or heated in a microwave oven to remove moisture) can reduce the drying time in a controlled manner when using aqueous adhesives. Water-based materials and methods should be avoided when hinging ink jet images, especially if the design is flush with or near the edge of the support, as the media is readily water-soluble. The alternative to water-based adhesives, synthetic adhesives can be irreversible, cross link, and discolor. Synthetic adhesives, such as Lascaux™ 360 HV and Rhoplex™ 580N, on Japanese papers have been used as temporary hinges for short-term exhibitions. Both adhesive batches passed the Photographic Materials Test (PAT) in 1996, but can have little cohesive strength and can develop cold-flow problems with long-term use. The validity of using the PAT test to determine the suitability of synthetic adhesives has been questioned. In recent decades, commercial companies have developed pressure-sensitive adhesive tape products marketed for repair, hinging, and mounting of photographic materials. Terms such as "inert," "acid-free," "archival," and "passed the PAT" have been used in advertisements. While conservators have not extensively used commercial pressure-sensitive tapes for exhibition mounting, instances may occur where short-term, temporary use seems justified on materials that can withstand subsequent removal of the adhesive tape without damage. It is likely that pressure-sensitive tape products are used on photographic materials in the commercial and private sector. Proprietary product compositions are changed without notice and extensive, long-term testing by the conservation community has not yet occurred. Likewise, the use of synthetic dry mount adhesives by conservators for mounting photographic images remains controversial. The Society of American Archivists series (Ritzenthaler et al. 1985, 128) states, "Dry mounting, is potentially irreversible, and is acceptable only for expendable copy prints." Dry mounting can also be viewed as the only viable solution for hinging and mounting works that may be water resistant (as with resin­coated or plastic-based prints) or are very large and heavy. Many photographers and conservators have commented on the protective quality of an overall dry mount layer when a poor-quality, acidic wood-pulp mount was originally used. When a good-quality mount is used, the process has been the method of choice and is recommended by conservators for mounting contemporary photographic materials. Prints mounted overall tend to distort less with minor fluctuations of temperature and humidity. Multi-media or large, oversize modern pieces have been displayed in the short term with commercial dry mount and other synthetic adhesives used to attach hinges of paper or polyester webbing (Watkins 1993, 1994). The use of a synthetic adhesive activated under heat should be considered thoroughly before use on materials that did not originally have such treatment. Some synthetic adhesives are known to cross-link with different types of materials; heat has been documented to increase the rate of degradation in materials, and solvents may not be a safe removal option for the image or signatures, photographer's stamps, and other additions. Mounting resin-coated prints to rigid supports, such as aluminum, that remain impermeable to organic solvent treatments, limits reversibility and removal attempts (Watkins 1993, 1994). . For exhibition and transport the Polaroid Corporation (1983, 29-30, 33) recommend the follOWing: Use die-cut corner mounts in a good-quality paper board or archival paper corners that are held to the backboard with archival library linen tape, or mount Polaroid® black-and-white and Polacolor® prints. On mounting, "integral films should not be heat mounted. Polaroid photographs should not be subjected to temperatures higher than 180T (82°C) and should not be left in the heated press for longer than 30 seconds. Kodak [Type] 2 Dry Mounting Tissue™, Ademco Low-Temperature Dry Mounting Tissue and Seal Low Temperature Mounting tissues are satisfactory. Lamin-All, from McDonald Photo Products, Inc., is a suitable liquid adhesive for mounting Polacolor® prints. It can be used either cold or under heat. When you mount Polaroid® coated black-and-white prints place the materials into the mounting press so that the mounting board faces the heated surface of the press and the print faces away from the heated surface." Since 1983, some conservators have expressed concern over the use of heat in part because of the complexity of dye diffusion transfer materials. The long-term, potentially damaging effects from heat should be considered prior to dry mounting Polaroid® material, especially unique work.

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