A-D strips

Film base deterioration monitors - Test strips for atmospheric acidity The Safe and Accurate Way to Check Film for Vinegar Syndrome and a Short-Term Test for Atmospheric Acidity in Showcases and Storage Areas Information and prices last modified: 1/05

The vinegar syndrome

Poor storage conditions can cause cellulose acetate film to undergo a slow form of chemical deterioration known as the "vinegar syndrome." As the film degrades, it gradually shrinks, becomes brittle, and generates acetic acid which evaporates into the air, producing a sharp, vinegar odor. A-D Strips represent a safe and reliable method for detecting, measuring, and recording the severity of vinegar syndrome in acetate photographic film collections.

Colour 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. They change, as the level of acidity increases, from their original blue color to blue-green, then to green, to yellow-green, and finally to bright yellow. The kit includes a reference pencil printed with four bands of color, numbered from 0 to 3, that correspond to the 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 information tells collection managers how far deterioration has progressed and whether existing storage conditions are good enough to preserve their film. Knowing this makes it easier to set priorities for film duplication.

The main purpose of A-D Strips is to determine the approximate extent of acetate support degradation in individual films, but they may also be used as a survey tool for gaining an overview of the condition of films in an entire collection and for providing a very accurate picture of storage and duplication needs. A-D Strips can be used with acetate sheet and roll film, cinema film, and microfilm.

Film consists of three principle components: a transparent plastic support, a gelatin emulsion, and an image of color dyes or metallic silver (see illustration). Three different 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.

The User's Guide can be downloaded here for free. It is provided with each pack of A-D strips and gives detailed information about minimum exposure time (24 h at room temperature, 1 - 2 weeks at 13°C...), evaluation of results and how often to recheck.

The IPI Storage Guide for Acetate Film (see below) offers a full discussion of film history, identification, deterioration, and storage recommendations.

Proper storage

A diagnostic tool like A-D Strips is only one part of managing the vinegar syndrome problem. The most important aspect of preserving acetate film is proper storage. All acetate and nitrate film, not just diacetate or certain types and brands of film, are prone to degradation. The process of deterioration goes on every day. How slowly or quickly it occurs depends on the temperature and relative humidity (RH) of the storage environment.

It is a simple fact that at room temperature and moderate RH acetate film will begin to seriously degrade in about 50 years. Periods of higher temperature and dampness will accelerate the process, and cold and dry periods will slow it down. Film stored in cool (less than 50°F, 10°C) conditions at moderate RH (20% to 50%) can be expected to last for centuries.

Film stored under poor conditions may become degraded within a few decades. Color film benefits doubly from cold storage. Cold conditions not only stabilize the film base but also minimize the rate of color dye fading (cf. ANSI Standard IT9.11-1994 and ISO Standard 5466-1992 provide recommended storage conditions for photographic films).

Test for atmospheric acidity

A-D Strips can also be used as a quick, short-term test of atmospheric acidity in a showcase or storage area. The table below shows A-D Strip levels as they relate to the concentration of acid vapors in the air in parts per million. This relationship was defined in the laboratory by estimating the concentration of acetic acid in the air inside pouches containing films at various stages of degradation using, simultaneously Draeger diffusion tubes and A-D Strips. The values are approximate, but they indicate a direct correlation between the two methods of measurement.

Further data see User's Guide.

Prices A-D strips: (generally in stock or available within 10 days) Order

The IPI Storage Guide for Acetate Film
by James M. Reilly, published by the Image Permanence Institute

The IPI Storage Guide is a four-part publication that explains the effect of temperature and humidity on the rate of film base degradation. It is an important tool for evaluating and planning storage environments for all types of acetate base film, cinema film, and microfilm. The 24-page booklet discusses environmental specifications for film storage and explains the relationship between temperature, relative humidity, and the time it takes for "vinegar syndrome" (the slow, chemical decomposition of acetate plastics) to begin to affect fresh film. Valuable quantitative data is offered in three easy-to-use forms: a wheel (a kind of circular slide rule) with temperature/humidity data and corresponding film life expectancies, graphs, and a time-out-of-storage table. A valuable collection management tool!

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