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