Enclosures for Glass and Film Negatives and Lantern Slides

Negatives and lantern slides are stored vertically in standard size chemically stable boxes placed on sturdy metal shelving or cabinets. Reinforced vertical filing cabinets provide another storage option, especially for plastic film negatives.

However, filing cabinets are dangerous for the storage of glass negatives and lantern slides because the filing cabinets may tip over when heavy top drawers are opened. In addition, the plates may be jostled and inadvertently broken when the cabinet drawers are opened and closed.

Unbroken glass plates larger than 8in x 10in are stored vertically in specially constructed metal cabinets with rigid vertical dividers spaced every 1-2in along horizontal shelving (Fig. 2).

Figure 2. Glass plate storage cabinet with metal vertical dividers to store plates that are not in boxes.

Stacking plates horizontally is dangerous since many glass plates are slightly warped and may be broken from the weight of the stack.

Boxing large plates for vertical storage may be dangerous since boxes become heavy and may not be strong enough to hold the weight load if picked up.

• Cotton gloves, lint-free
• Metal cabinets
• Metal shelving
• Paper envelopes, seamed, alkaline buffered, pH 7-8.5, ANSI IT9.2-1991 specs., 4in x 5in, 5in x 7in, 8in x 10in, etc.
• Paper envelopes, seamless, alkaline buffered, pH 7-8.5, ANSI IT9.2-1991 specs., 4in x 5in, 5in x 7in, 8in x 10in, etc.
• pH neutral paper board
• Photographic storage boxes, alkaline buffered, pH 7-8.5, ANSI IT9.2-1991 specs., 4in x 5in, 5in x 7in, 8in x 10in, etc.

Film Negatives

1. Purchase a sufficient number of envelopes for all film negatives.
2. Wearing cotton gloves, house each negative in an individual envelope, being careful not to scratch the emulsion with the envelope upon insertion.
3. Position negatives so that the emulsion, or image, side of the negative faces away from the seam to minimize the chance of fading or staining occurring on the front.
4. Store the envelopes vertically on their long edges in sturdy, lidded boxes (Fig. 3).
   
   
   Figure 3. Box with hinged lid for storage of negatives
   
   
5. Clearly label boxes with CAUTION, FRAGILE, GLASS and HEAVY signs.

Contemporary safety film negatives, most commonly tri-acetate or polyester film, can be safely housed in archival plastic sleeves such as polyester, polypropylene, or polyethylene (See Norris, in press). Unknown plastics, or polyvinyl-chloride plastic (PVC), should be avoided because plasticizers may contaminate the surface of the enclosures and harm the negative.

Glass Plate Negatives

1. Purchase or make envelopes with three or four flaps to protect each plate.
2. Wearing gloves, position each plate face down in the center portion of the envelope.
3. Fold in flaps.

Broken Glass Plate Negatives

1. Construct sink mats (See Conservation Center for Art and Historic Artifacts, “Enclosure for Broken Glass Plate Negatives”, this volume) to house broken glass plate negatives and those with flaking, cracked or broken gelatin emulsions.
2. In the interim, sandwich the broken negatives between two sheets of pH neutral paper board.
3. Store each plate in a four-flap envelope to keep the plate pieces together and to prevent further damage.
4. Box each plate separately.
5. Clearly indicate on the box label that the plate is broken.

Historic Negatives

(nitrate and acetate film)

Store historic nitrate and acetate film in individual alkaline buffered paper envelopes to help neutralize acidic offgassing as these films degrade.

There are two types of paper envelope designs available — seamed and seamless (Figs. 4, 5). Seamed envelopes have a side and bottom seam which form a pouch enclosure. Seamless envelopes have three or four flaps which fold up to enclose the negative inside.

Figure 4. Seamed envelope.


Figure 5. 3-flap seamless envelope, open to show how flaps close in.

Seamed envelopes may cause abrasion of the negative as the object is inserted and removed from the enclosure. In addition, seams may emboss the negative, or poor quality adhesives used in the seam may cause localized fading and staining. For these reasons, envelopes with center seams should not be used.

Seamless envelopes are bulky, slightly more expensive, and more cumbersome to use. Their advantage is that abrasion is less likely, there is no seam adhesive to cause deterioration of the photograph, and these envelopes have flaps that are scored to accommodate the extra thickness of the glass plates.

The paper stock used in the enclosures and storage boxes should be of high quality, lignin-free, sulfur-free, alum-free, pH 7-8.5 paper, which meets the requirements of the American National Standards Institute (ANSI) IT9.2-1991 specification of photographic storage enclosures, including the Photographic Activity Test.

Although it may not be practical to store large collections of lantern slides in sleeves, especially if the slides retain their protective cover glass, all those that have lost their cover glasses should be housed in envelopes to protect the exposed emulsion.