Putting It Into Practice

Evaluating Your Collections

Negatives and Transparencies

Photographic negatives and transparencies in your collection may include glass plate negatives, lantern slides, autochromes, black and white film negatives, color film negatives, and color slides. Older film negatives may be on nitrate film, while newer ones are likely on acetate or polyester film.

This water-damaged gelatin glass plate negative exhibits mold growth and flaking emulsion along the left edge/side.

Types of physical damage you may observe include broken or cracked glass plates or covering glass, broken tape seals on lantern slides or autochromes, and cracking or flaking of glass plate emulsions. Mold growth may also be a problem.

Evidence of chemical damage due to the deterioration of nitrate film may include yellowing, stickiness, and a nitric acid odor. Nitrate films that are in an advanced state of deterioration will be soft and may adhere to adjacent films or enclosures, or they may have partially disintegrated into a brown powder. Evidence of chemical deterioration of acetate film due to vinegar syndrome may include a vinegar odor, curling, or staining. Advanced deterioration will manifest itself through bubbles on the film and separation of the emulsion from the base. Nitrate or acetate film may sometimes be identified by edge printing (it will say NITRATE or SAFETY).

Deteriorated color negatives and slides may show evidence of fading or color change (dye shifts).