Exploring

External Factors

Environment

Temperature

As we have seen, higher temperatures increase the rate of the chemical reactions (oxidation and hydrolysis) that drive deterioration. This is particularly important for film-based and optical media, since many of these materials deteriorate at a rapid rate at room temperature (generally accepted as 68°F and 50% relative humidity). Cellulose nitrate film may show significant deterioration in as little as 10 years (although it may also survive significantly longer), and cellulose acetate film has a life expectancy of only about 40 years. Temperature also accelerates the fading of color materials.

Relative Humidity

This audio tape reel has developed mold on the edges of the tape due to high relative humidity.
Courtesy of Stanford University Libraries

Humidity (moisture in the air) provides water to fuel the chemical reactions that cause deterioration. The more moisture there is in the air, the more quickly chemical deterioration proceeds. High humidity is a primary factor in hydrolysis, which affects binder degradation, fading of color dyes, and deformation of film and tape supports. Fluctuating humidity levels also accelerate damage, particularly affecting distortion of CDs, DVDs, and magnetic tape backings.

Pollutants

Film-based, magnetic, and optical media are particularly vulnerable to the effects of gaseous and particulate pollutants. Particulate pollutants cause abrasion, and many gaseous pollutants are oxidizers, contributing to the deterioration of color dyes, silver images, the reflective surfaces of CDs and DVDs, and magnetic tape binder materials.

The cyan and yellow dyes in this slide have faded, leaving only the magenta color. The shift of color dyes can be exacerbated by storage in a high-humidity environment.

Light

Exposure to light greatly accelerates the fading of the color dyes used in various types of film-based materials, as well as the dyes used in R (write once) CDs and DVDs. Exposure to strong sunlight can also cause damage due to the resulting heating of the exposed materials. Color slides in particular are very vulnerable to fading when projected in a slide projector (due to both heat and light exposure). It is important to note that Kodachrome slide film is very stable in the dark but fades rapidly when exposed to light, while Ektachrome slide film is more resistant to projection damage but fades more quickly than Kodachrome in dark storage. Fujichrome is generally the most stable slide film overall.