I get messaged a lot and asked about Tannins or color discoloration...
So here's a breakdown:
Brownish or tan discoloration on the paint surface due to migration of tannins from the substrate (e.g., the surface that was painted) through the paint film. Tannins exist in many woods. Typically in staining woods like redwood, cedar, and mahogany, or over knots in certain other wood species. Tannins can bleed through to the surface, leaving a yellowish-brown stain on the surface. These stains are more noticeable on lighter paint colors.
WHAT CAUSES IT?
- Failure to adequately prime and seal the surface before painting.
- Humidity or other moisture problems that can cause tannins to rise to the paint surface
Tannin staining can occur with any kind of wood. Most tannins are water-extractive, some are solvent-extractive. Humidity vs. chemical.
- Locate and correct any moisture sources.
- Remove all loose paint with a scraper or wire brush.
- Wipe down and clean the piece. Dixie Belle White Lighting will clean and knock down the gloss from the wood. It works like TSP. Take a bowl or water and rinse after use.
- Remove the stains with oxalic acid or wood bleach. (I use Oxalic acid from Home Depot: Eco Clean Pure Oxalic Acid Powder)
- Allow the surface to dry thoroughly for at least 48 hours. If you are painting outdoors, and it's humid, I would wait longer.
- Prime the stained area with a top-quality, stain-blocking wood primer. Dixie Belle Paints BOSS works great.
- If severe staining exists, apply two coats of primer/BOSS. Always prime edges and the ends of the piece.
- Repaint using high-quality paint. Of course, I recommend Dixie Belle Paints. It works well after using solutions above.
Tannin bleed is a surface problem with the furniture, not a paint failure.
Yes, many mineral based paint projects can be easily painted with little to no prep but that is not usually the case with a thrift store or curb side finds. As a furniture painter, I prep all my pieces. Even clean, sand then paint the cleanest looking item. But it's not necessary. That's just MY process. We're all different.
I have even found myself waiting for my primer to cure for a few days with mahogany. Mahogany and teak is not my friend... more of my Nemesis...lol. If staining occurs during the application of the new coat of paint, sand lightly and re-prime the area before applying the coats of paint.
Happy Painting ~ Rose