Q. What’s the best way to treat new white cedar shingles to give them a gray, weathered look?

A.Martin Obando, director of application specifications for the Cedar Shake and Shingle Bureau, responds: If your customer is unwilling to wait for the natural weathering process, new cedar shingles can be either stained or treated with bleaching oil.

Using a gray semi-transparent stain is the fastest way to change the color of new shingles. It is important to choose a stain that includes a fungicide, since fungus can cause black stains on cedar shingles.

Bleaching oil, which is available from Cabot Stains (800/877-8246), requires the action of sunlight to change shingle color. Bleaching oil accelerates the natural weathering process and will turn new cedar shingles a uniform gray in 6 to 12 months.