Exposure of protective coatings on aluminum foil to the action of ultraviolet and visible radiation can accelerate the rate of change within the films by a factor of almost 2. The use of the aluminum foil as a support also facilitates the weighting of films. By this method both the loss of weight to volatilization and the change in solubility can be determined. An analysis of the rate of change of the fraction of a thermoplastic polymer that remains soluble, considered as a function of the time of exposure can reveal the ratio of chain breaking to liking in the film.