Preventing Wood Tannin Bleed-Through in Paint
Definition: Tan or brownish discoloration on the paint surface. Tannins exist in many woods, most notably cedar and redwood and can bleed through to the surface, leaving a yellowish-brown stain on the surface. These stains are more noticeable on lighter paint colors, known as Painting Tannin Staining.
CAUSES:
* Failure to adequately prime and seal the surface before painting
* Using a primer that is not Painting Tannin Staining-resistant
* Excess humidity or other moisture problems that can cause Painting Tannin Staining to rise to the paint surface
PAINTING TANNIN STAINING SOLUTIONS:
* Locate and correct any moisture sources.
* Remove all loose paint with a scraper or wire brush.
* Remove the stains with oxalic acid or an oxalic-based solution.
* Rinse with a pressure washer, to remove Painting Tannin Staining.
* Allow the surface to dry thoroughly for at least 48 hours (depending on the existing weather conditions).
* Prime the stained area with a top-quality, stain-blocking wood primer.
* If severe staining exists, apply two coats of primer. Always prime edges and ends of shingles. If possible, prime the backs of shingles prior to installation.
* Repaint using high-quality paint, to terminate Painting Tannin Staining.
