Brownish or tan discoloration on the paint surface due to
migration of tannins from the substrate through the paint
film. Typically occurs on “staining woods,” such as
redwood, cedar and mahogany, or over painted knots in
certain other wood species.
Possible Causes Tannin Staining Paint
Failure to adequately prime and seal the surface before applying the paint.
Use of a primer that is not sufficiently stain-resistant.
Excess moisture escaping through the exterior walls, which can carry the stain to the
Solution Tannin Staining Paint
Correct any possible sources of excess moisture (see Efflorescence and Mottling). After
thoroughly cleaning the surface, apply a high quality stain-resistant oil-based or acrylic latex
primer. Oil-based stain-resistant primers are the best type to use on severely staining
boards. In extreme cases, a second coat of primer can be applied after the first has died
thoroughly. Finish with a top quality latex paint.