Volume 10, Number 3, Sept 1988, pp.3-6

Photographic Enclosures

This is a revised version of an article by Ms. Walsh which originally appeared in the Association of Canadian Archivists Bulletin, Vol 11, no 2 (Nov 1986) and Vol 11, no 3 (Jan 1987).

Part I: Storage Materials

Selecting a photographic enclosure is not as simple as choosing other archival storage materials. Amongst the variety of enclosures available, no single product is ideal for all purposes. Archivists must make informed choices according to their own circumstances.

Initially, the enclosure must be made of materials that will not chemically or physically damage photographs. Given the youth of photographic conservation, these materials are still being actively researched. A good starting point for materials is American National Standard IT 9.2 - 1988¹ published by the American National Standards Institute (ANSI). (This is a revised and renamed version of ANSI PH 1.53 - 1986.) Keep this in mind when reading the fine print in archival suppliers' catalogues.

ANSI requires that all enclosures should be chemically stable and free of acids and peroxides. The materials should pass an accelerated aging test known as the photographic activity test.

Paper enclosures that are in direct contact with the photograph should be made of rag or wood pulp that is either bleached sulphite or bleached kraft. The alpha cellulose content of the wood pulps should be greater than 87%. Specifications are also given for a minimal, neutral size (e.g. no alum) and an absence of lignin, metals, waxes, plasticizers, and free surface fibers. Glassine papers are prohibited.

Unlike most paper documents, photographic images do not necessarily benefit from alkaline conditions. In fact, excessive alkalinity is suspected of deteriorating color photographs, cyanotypes, and albumen prints. Hence the ANSI requirements for pH and alkaline reserve depend on the photograph: for black and white, pH 7.2 - 9.5 with an alkaline reserve; for color, pH 7.0 - 7.5 without the reserve. For albumen prints, the evidence is incomplete but enough to recommend "unbuffered" papers to archivists buying new enclosures^2,3.

Because the effects of alkalinity are still being researched, some conservators recommend pH neutral, unbuffered enclosures for most photographs⁴. Buffered enclosures are still recommended for inherently acidic photographs, such as nitrates and platinum prints⁵.

ANSI recommends plastic enclosures made of clear, uncoated polyester (poly(ethylene terephthalate)), cellulose triacetate, polyethylene and polypropylene. Acceptable tradenames for polyester are DuPont Mylar D and ICI Melinex 516.

Some polyester sleeves are constructed of a frosted Mylar, type EB 11, which has silica embedded in it. This is designed to prevent ferrotyping, spotting, and glossing of the emulsion against a smooth surface at high humidities. Since some conservators suspect the silica could abrade the emulsion, it may be wise to avoid this material.

Certain plastics and components of plastics are forbidden: chlorinated and nitrated sheeting, coatings, residual solvents, and large concentrations of plasticizers. Typical bad examples are the binder pages made of highly plasticized polyvinyl chloride (PVC) that are frequently sold by camera stores.

Research by Scott Williams of the Canadian Conservation Institute suggests that polystyrene is also a suitable material. It is used at present in slide mounts, carousel slide trays, and certain slide dividers⁶.

On a broader scale, James Reilly, director of the Image Permanence Institute, tested a selection of enclosure materials with albumen prints, using the PH 1.53 version of the ANSI photographic activity test⁷. While the plastic enclosures passed the test, many papers did not. The reason, according to Reilly, is: "Plastics are more homogeneous than paper and their composition can be carefully controlled."⁸. Rag papers performed better than wood pulp papers. Colored mat boards, particularly black ones, were the most harmful. Overall, Reilly recommended plastic enclosures, but he will accept paper enclosures if they are tested⁹.

Once you have the materials, how should the enclosures be put together? In the past, envelopes with gummed centre seams deteriorated photographs. ANSI specifies adhesives and certain enclosure formats. Initially, the adhesive and any printing inks should pass the photographic activity test. And, amongst other stipulations, the adhesive should not be hygroscopic or pressure sensitive; envelopes should have a bottom fold and narrow edge seams. As a final precaution, the photograph should be stored facing away from the seam.

Other construction methods are available beside those designated by ANSI. Some conservators mistrust adhesives and seams so much, they recommend three or four flap seamless envelopes¹⁰.

Archivists and conservators can perform a few simple tests to cull out the worst enclosures. Basic paper spot tests will detect alum, lignin, and low pH. It is a good idea to periodically spot test the enclosures you buy, since quality can vary. For plastics, a burning test known as the Beilstein test will detect chlorine. If you are interested in this method, Scott Williams has outlined it in an IIC-CG Newsletter¹¹.

Additional analysis requires scientific expertise. To complicate matters, conservation scientists have been searching for a definitive test that will predict the effects of enclosures on photographs. In the literature you will find references to Collings and Young's silver tarnishing test¹², which has fallen out of use because it cannot be applied to photographic emulsions.

There were also problems with the Photographic Activity test published in the previous ANSI standard. James Reilly found that the test detected the worst enclosures, but not those in the gray zone between good and bad. As a result, ANSI IT 9.2 - 1988 has a new Photographic Activity Test with two more sensitive detectors¹³.

Conservators can test their enclosures for themselves, or arrange for the Image Permanence Institute to do it. For information, contact the Image Permanence Institute, RIT City Center, 50 West Main St., Rochester, NY 14614, (716) 475- 5199.

Selecting a photographic enclosure is far more complicated than choosing storage materials for prints and drawings. Be sure to avoid mystery materials. Buy from an archival supplier, using the criteria discussed above.

Part II: Choosing Enclosures to Meet Your Needs

The choice of enclosure materials and format depends on the particular collection and storage area. Although a variety of enclosures meet the criteria discussed previously, each type has its own advantages and disadvantages. The features are reviewed by Hobbie¹⁴, Albright¹⁵, and ANSI IT 9.2 - 1988.

Think of your own circumstances and ask yourself the following questions:

• What types of photographs do you have?

  Since paper enclosures are porous, gases can escape. They are advised for nitrates and early acetates. Other photographs are also suited to paper enclosures and are listed below.

• What are your environmental conditions?

  Enclosures are a second line of defense after environmental controls; some enclosures suit environmental extremes better than others. Is it far more humid than standard (especially if above 65%, with extreme fluctuations)¹⁶? If so, there is a risk that the emulsion could ferrotype (spot and gloss) against plastic enclosures. Are the photographs adequately protected from light by file drawers or document boxes? If not, paper envelopes are preferred. Likewise, if containers (or lack thereof) do not keep out atmospheric contaminants, then envelopes are desirable.

• What is the access situation?

  Customarily, researchers should be looking at reference copies. If originals must be handled, note that frequent removal from paper envelopes increases the chances of scratching and fingerprinting and therefore folders and plastic enclosures would be preferred. While folders are easy to use, remember that haphazard handling can damage the photograph.

• What about labeling?

  It is easier to write on paper than plastic.

• What containers are you using - file drawers, boxes, binders, or open shelving?

  Make sure the components physically fit each other.

• Finally, what is your budget?

Part III: Types of Enclosures

With the above questions in mind, review the enclosures available. The major kinds of photographic enclosures are listed below. If a wider choice is required (with a detailed list of pros and cons) the reader is encouraged to read the Hobbie and Albright references. Except for the first entry, the enclosures are not listed in order of preference. The cost is for an 8" x 10" photograph (based on price per 100 sleeves), in U.S. funds without shipping costs. Prices are approximate and vary considerably between suppliers for the same kind of enclosure.

There are many options for 35mm transparencies. Slides can be stored in bulk in: the polypropylene boxes returned by Kodak (until 1986) after processing; baked enamel storage boxes and cabinets; and polystyrene carousel trays and cubes. Slides can be stored flat in polyethylene and polypropylene pages. If you use binders, buy cloth binders from archival suppliers and not the PVC ones.

As followers of photographic conservation will know, the information on enclosures is constantly changing. However, don't race into adopting new materials until they are approved by conservation scientists.

Finally, I would like to thank Dr. Klaus Hendriks of the Public Archives of Canada, Scott Williams of the Canadian Conservation Institute, and Douglas Nishimura of the Image Permanence Institute; they shared many insights from their research on enclosures.

Notes

1. American National Standards Institute, American National Standard for Photography (Processing) - Processed Films, Plates, and Papers - Filing Enclosures and Containers for Storage. ANSI IT 9.2 - 1988. New York: American National Standards Institute, 1988.

2. James M. Reilly, "Albumen Prints: A Summary of New Research about their Preservation," Picturescope 30 (1982):34-36.

3. Ellen McCrady, "Does Alkaline Buffering Affect Photos? Hard to Tell." Abbey Newsletter 8 (October 1984):68.

4. Debbie Hess Norris, "The Proper Storage and Display of a Photographic Collection," in The Book and Paper Group Annual, vol. 2, Edited by Craig W. Jensen. Austin: AIC, 1983, p. 69.

5. Gary Albright, "Which Envelope? Selecting Storage Enclosures for Photographs," Picturescope 31 (winter 1985):112.

6. R. Scott Williams, "Commercial Storage and Filing Enclosures for Processed Photographic Materials," paper presented at Second International Symposium: The Stability and Preservation of Photographic Images, Ottawa, August 25-28, 1985, p. 19.

7. James W. Reilly, "Evaluation of Storage Enclosure Materials for Photographs Using the ANSI Photographic Activity Test," Final Narrative Report of Accomplishment for National Museum Act Grant #FC-309557 (March 1984).

8. James M. Reilly, Care and Identification of 19th Century Photographic Prints. Kodak Publication G-25. Rochester: Eastman Kodak, 1986, p. 93.

9. Ibid, p. 93.

10. Mary Lynn Ritzenthaler, Gerald F. Munoff, and Margery S. Long, Archives and Manuscripts: Administration of Photographic Collections, SAA Basic Manual Series. Chicago: Society of American Archivists, 1984, p. 100.

11. R. Scott Williams, "The Beilstein Test," IIC-CG Newsletter 9 (Dec. 1985):15-19.

12. T. J. Collings and F.J. Young, "Improvements in Some Tests and Techniques in Photograph Conservation," Studies in Conservation 21 (1976):79-84.

13. James M. Reilly, "Improvements in Test Methods for Photographic Storage Enclosures," paper presented at SPSE's 40th Annual Conference and Symposium on Hybrid Imaging Systems, Rochester, New York, May 20-21, 1987, pp. 151-154.

14. Margaret Hobbie, "Paper and Plastic Preservers for Photographic Prints and Negatives," History News 35 (October 1980):42-45.

15. Albright, "Which Envelope," p. 111-113.

16. Hess Norris, "Storage," p. 70.

17. Klaus B. Hendriks, The Preservation and Restoration of Photographic Materials in Archives and Libraries: A RAMP Study with Guidelines. Paris: Unesco, 1984, p. 76.