Coatings prepared from t wo blown petroleum asphalts in a t hickness r ange of 0.002 t o 0.04 inches were exposed to accelerated test condit ions and ou tdoors. When exposed to light only, a surface film, insoluble in common asphalt solvents, was formed. The formation of t his s urface film was accompa nied by a gain in weight of the coatings, apparently due to an oxygen pickup . This surface film retarded fur th er d egradat ion of t h e m alt enes during tile exposures made to light only. ' When t he coatings were immersed in wate r after expos ure, or sprayed with water during exposure, or exposed outdoors, they lost weight. These decreases in weight were found to be in part du e to the extraction of water-soluble, ligh td egraded m ate rial. Their m agnit ud es wer e dependent upon th e as phalt exposed, the thi ckn ess of t he exposed coatings, and the exposure co ndi tions. The relationship between t h e losses in weight and water-soluble m a terial, when consid ered in conjunction with the oxygen content of the asph alts and t h e water-soluble mate rials, i ndicated that volatile d eg radation produ cts were also form ed.When t he surface s kin formed by t h e a ction of ligh t was pftrLially rem oved b y washing wit h water, p ercentage d ecreases were noLed i n t h e water-white o ils, dark oils, and aspha ltic r es ins. Sin ce these d ec reases were unequal in m ag ni t ud a nd sin ce the losses in weigh t w ere d epend ent on t he thickn ess of t h e coating, it was concluded t h'Lt li gh t-deg radable components of the asphalt h ad migraLed to the surface to replace d eg rad ed maLerial that had been washed m\·ay.