Research on Image Stability and Film Base Decay

A-D Strips in film canIn response to concerns about the stability of silver image (in black & white photographic film) and the conclusions of research done by the National Bureau of Standards and Eastman Kodak (silver oxidation was caused by peroxides given off by deteriorating poor-quality cardboard storage boxes or atmospheric pollutants), IPI developed a test for evaluating a film's susceptibility to silver oxidation. This test became ISO Standard 18915. Another outcome was IPI SilverLock, an after-processing treatment that drastically increased the oxidation resistance of silver particles.

IPI research found a strong relationship between the stability of color photographic images and storage temperature and humidity. Color prints and film are likely to deteriorate after only a few decades if stored at room conditions but would last for centuries if stored at cold temperatures. Results were published in IPI's Storage Guide for Color Photographic Materials, named publication of the year in 1998 by the Society of American Archivists.

Until the 1980s, the only information regarding the stability of cellulose nitrate, the plastic film support commonly used in the late 19th century, was anecdotal. Collection managers had no real preservation strategy for dealing with the highly flammable material. IPI researchers studied nitrate film samples at different temperature and humidity levels and found that some were relatively unstable while others were actually more stable than acetate films. This work resulted in the recommendation that only nitrate films showing signs of developing degradation should be duplicated and these should be copied onto a polyester film base or digitized. Low storage temperature can significantly improve the stability of nitrate film, and if any decay is present, very cold conditions are advised.

Acetate film supports were intended to be more stable than nitrate until instances of cellulose triacetate instability or "vinegar syndrome," began to be reported. IPI completed extensive research using the Arrhenius approach to evaluate the stability of acetate films incubated at various temperatures and relative humidity levels. Of all the properties measured after incubation, acidity generation proved to be the most sensitive indicator of acetate base decay. This ground breaking study firmly established the relationship between film base decay and storage environment and resulted in the development of IPI's award-winning A-D Strips and the IPI Storage Guide for Acetate Film.