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A-D Strips are dye-coated paper strips that detect and measure the severity of acetate film deterioration, a.k.a. vinegar syndrome, in film collections. The strips are sold in packages of 250 and come with a user's guide (download PDF) and a pencil printed with bands that serve as color references. Price: $60 each for 1 to 9 packages, $48 each for 10+ packages.
Color Changes Tell the Story
When placed inside a closed can, bag, box, or cabinet, A-D Strips change color in the presence of the acidic vapor given off by degrading film. As the level of acidity increases, they change from their original blue color through blue-green, green, and yellow-green, and finally to bright yellow. The reference pencil included in the kit is printed with four bands of color, numbered from 0 to 3; these correspond to strip colors at four levels of acidity. After exposure to film in a sealed enclosure for the required length of time, the strip color is compared to the color bands on the pencil. The number of the band most closely matching the color of the strip is recorded.
This shows collection managers how far deterioration has progressed and whether existing storage conditions are good enough to preserve their film. They can then set priorities for further actions, such as improving storage conditions or setting up a film duplication program.
Use A-D Strips to learn the approximate extent of acetate degradation in individual films, or use them as a survey tool for gaining an overview of film condition in an entire collection and to get a more accurate picture of storage and duplication needs.
Three types of plastic have been used in film manufacture: Nitrate was used from 1890 to 1950, acetate from 1925 to the present, and polyester from 1960 to the present. A-D Strips are recommended for use only with acetate film. The film may be in any format: sheet film, roll film, cinema film, or microfilm.
For a full discussion of film history, identification, deterioration, and storage recommendations, see the IPI Storage Guide for Acetate Film.
Interpreting A-D Strip Results
A-D Strip Level
|0||Good—no deterioration||Cool or cold storage|
|1||Fair to Good—deterioration starting||
|1.5||Rapid decay starting—point of autocatalytic decay||Cold or frozen storage|
|3||Critical—shrinkage and warping imminent, possible handling hazard||
Relationship Between A-D Strip Levels, Free Acidity, and Film Condition
There is a direct correlation between A-D Strip levels and the state of preservation of film. Note that the curve becomes markedly steeper after it reaches the autocatalytic point, illustrating the rapid increase in the rate of film decay.
Technical Achievement Award
IPI received a Technical Achievement Award from the Academy of Motion Picture Arts and Sciences in 1997 for developing A-D Strips.