• Manifestations
  1. Tannins from the substrate migrate to the surface of the paint film causing tan or brownish discoloration.
  2. This is typically found on cedar, mahogany and redwood, or over painted knots in some other kinds of wood.
• Causes
  1. Inadequate priming and sealing before applying paint to the surface.
  2. Using a primer that does not provide sufficient stain resistance.
  3. If excess moisture escapes through the exterior walls, it can carry a stain to the surface of the paint.
• Solutions
  1. Correcting possible sources of excessive moisture. Read section on Efflorescence and Mottling.
  2. Clean surface thoroughly and apply a high quality acrylic latex or stain resistant oil-based latex primer. c
  3. When working with severely stained boards, oil-based stain-resistant primers work best. If you encounter an extreme case, apply a second coat of primer.
  4. Be sure to allow sufficient drying time between coats.
  5. Finally, apply a coat of top quality latex paint.