Under the influence of the ultraviolet portion in daylight sulfuric acid is produced at the surface that will gradually discolor the surface gray green to white and cause rapid deterioration of electric surface resistivity.
Under the influence of the ultraviolet portion in daylight hard rubber oxidizes and exposure to moisture bonds water with free sulfur on thge surface creating sulfuric acid at the surface. These aging processes will gradually discolor the surface gray green to brown and cause rapid deterioration of electric surface resistivity.