n.A laboratory procedure that estimates a material's rate of deterioration, making it possible to predict its life expectancy.Roberts and Etherington 1982 Although sound in theory, accelerated aging tests are, at this time, of limited usefulness. The reason is that conditions of storage, which vary widely, have a considerable influence on the degree of permanence; also, it is difficult to verify empirically the accuracy of such tests except by experiments conducted over a number of years.
Notes
Many tests are based on the Arrhenius function, which predicts that materials age in a predictable manner relative to temperature. By determining how long it takes for materials in an environment with an elevated temperature to reach a predetermined level of deterioration (brittleness, fading, signal loss), it is possible to project how long it will take materials at normal storage conditions to reach that level of deterioration. Because the level of deterioration is set arbitrarily, the test has a subjective aspect that makes results open to dispute. For example, the test may accurately predict the time it will take film to reach a predicted level of brittleness, but some individuals would find the film to be sufficiently pliable to remain useful.
