Painting over red cedar, cypress, and redwood can lead to tannin staining.
What Causes It?
Stains from the tannins in these woods are caused by a combination of moisture and insufficient sealing. Moisture can carry tannins contained in the wood through paint on the surface, and are likely to be visible especially with light or medium colors.
How to Solve It - Unpainted Wood
If your wood becomes stained when you are applying paint, use two coats of primer before you apply your topcoat. Be sure to wait 24 hours between coats after applying the first primer coat.
If stains occur, prime the stained spot again and allow it to dry. Then apply the finish coat. In some cases, it is best to allow new wood to weather for several weeks before painting.
How to Solve It - Painted Wood
Wash stained areas with a mixture of denatured alcohol and water. You can also use wood bleach (oxalic acid).
Rinse all treated areas well and let them dry thoroughly, and then apply one coat of your selected primer and topcoat.
Note: Images provided by The Rohm & Hass Paint Quality Institute.