Once coated with the appropriate thickness of asphalt, one side of the shingle is then
2
surfaced with granules for protection against physical damage, and damage from
ultraviolet rays of the sun. The granules which are exposed in the roofing application are
comprised crushed rock coated with ceramic metal oxides, and the headlap granules
are coal slag. Both types of aggregate are relatively uniform is size, most ranging from
0.3 - 2.36 mm, and both are hard and angular.