Several methods previously developed were used to further analyze the degradation processes in silk artificially aged by exposure to heat and ultraviolet light. Measurements of the tensile strength of warp yarns, color change and the development of ninhydrin reaction products were used to determine the effectiveness of various ultraviolet light sorbers and hindered amine light stabilizers in reducing degradation, the effectiveness of combinations and varying concentrations of these stabilizers in reducing degradation and the influence of temperatures on artificial ageing. Stabilizers evaluated included a benzophenone, a benzotriazole and several low basicity hindered amine light stabilizers, some of which had proved to be beneficial in reducing the rate of degradation in earlier work. The best performance by the stabilizers was obtained with a combination of 2per thousand of the benzophenone, Cyasorb 531, and 2per thousand of the hindered amine light stabilizer, Tinuvin 765. After exposure to ultraviolet light, this stabilizer combination allowed the silk to maintain over five times the strength of the unstabilized control, 60per thousand less color development and a 43per thousand decrease in the concentration of ninhydrin reaction products. None of the stabilizers examined provided protection against heating. Synergistic effects were obvious in this combination of stabilizers as well as others suggesting different stabilizers inhibit different paths of degradation. The influence of the ratio of stabilizers used in combination was also evident and important for achieving optimum results. An examination of silk fabrics artificially aged by heat showed that at heating temperatures of less than 100°C at reasonable exposure times (four days) increased the color of the silk but did not produce a statistically significant decrease in strength. The rate of strength and color degradation at temperatures from 100°C to 150°C, though, follow the Arrhenius relation. Activation energies were 29.10 kcal/mol for strength degradation and 16.09 kcal/mol for color degradation. Comparing the properties of silk artificially aged by heat with those artificially aged by light suggested that the two ageing techniques occur through different mechanisms since silk discolored by exposure to light was much weaker than silk discolored to the same degree by heat.