A plot of tensile strength versus time of exposure offers a good possibility for predicting absolute durability. The critical parameters in such a plot are the point at which inversion of the tensile strength occurs and the slope of the degradation of tensile strength beyond that time. This concept of durability has been found to correlate well with the known exterior durability of a wide variety of air drying and baking finishes. Judging results in accelerated weathering machines by similar tensile strength versus time curves gives good correlation with exterior exposure. This possibility of predicting exterior durability should be useful to the paint industry, especially when coupled with other relatively short term exterior exposure to determine such characteristics as mold and fade resistance.