Exposure of paper or board to a hostile environment, such as some types of radiation, elevated temperature, or chemical attack over a period of hours, may provide information concerning the natural changes that may occur in the material over a period of years.

Hostile environments that have been used include exposure to heat, to heat and moisture, to visible and ultraviolet radiation, and to sulfur dioxide gas.

Properties compared before and after such exposure include mechanical properties, such as folding endurance and tearing resistance, optical properties such as brightness and opacity, and chemical properties such as pH and alkali resistance. For additional information, see Test Methods D 828, D 829, D 919, D 2176, TAPPI Methods T 509, T 212, T 423, and T 425.

For determining the effect of moist heat treatment on paper see Test Method D 4714. It has been determined that the degradation of cellulose is very sensitive to moisture.^{5 ,6} Comparison of accelerated aging with natural aging indicates that some moisture should be present in an accelerated aging atmosphere.⁷ Dry accelerated aging of cellulose is much less sensitive and probably does not rank papers in order of stability as accurately as moist accelerated aging. Dry aging is much simpler to use and may be adequate for many purposes, but moist accelerated aging should be used where the greatest correlation with natural aging is needed.