What is extractive bleeding and how can we clean it off?
The Eastern white cedar that we use for manufacturing our shingles does not have a lot of tannin, compared to its cousin the Western red cedar. Nevertheless, extractive bleeding of wood may occur on the surface of our shingles, even more on those stained of a light color. Extractive bleeding is characterized by the wood tannins which are dissolved with moisture and which then migrate to the surface of the product. Rain will sometimes wash these stains away; however if left to weather, the sun can cause polymerization. If this happens, compounds containing oxalic acid or water/household bleach mix appear to be the most effective at removing extractive bleeding stains (ensure you use proper safety precautions and follow the oxalic acid compound manufacturer’s application directions). Extractive bleeding does not mean there was a defect in manufacturing or in the application of the finish, it is a natural phenomenon that occurs in applications. At SBC, we do everything we can to avoid ext
