Abstract: Volcanic ash is applied to hot asphalt roofing shingles during manufacture to maintain separation and inhibit color transfer between the shingles when stacked. Volcanic ash is separated into a fine particulate component which is a respirable dust and a remainder separating agent component which can be handled without respiratory equipment. After a roofing shingle core material such as an organic film or fiberglass sheet has been dipped into hot asphalt and colored roofing granules have been applied to one side of the hot asphalt-coated core material, the separating agent component is applied by spraying or gravity feed through a perforated plate to the opposite side of the hot asphalt-coated core material.