Patent ID: 8668954

Claim:
A process for producing algae-resistant roofing shingles, the process comprising producing algae-resistant roofing granules, and adhering the granules to a shingle stock material, wherein the process for producing algae-resistant roofing granules comprises: (a) providing porous, inert base particles; the base particles being prepared from a mixture including stone dust and a binder; the base particles being fired in a kiln to insolubilize the binder; and (b) providing at least one inorganic algaecide within the base particles to form algaecide-bearing particles; wherein the at least one inorganic algaecide is provided in the base particles after the base particles are fired, an algaecide-forming compound being dissolved in a fluid to form a solution, the solution being drawn into the pores in the base particles by capillary action to form solution-laden particles, the solution-laden particles being subsequently treated to convert the algaecide-forming compound to an inorganic algaecide.