Tannin Bleed
You know the dry bitterness that you taste from chewing a grape skin or the dry feeling in your mouth after you drink a glass of wine? That is caused by tannins.
Wood also has tannins, but since normal people don’t chew a lot of wood, you don’t notice them…Until they bleed through your paint! This is called “Tannin Bleed.”
Tannins are poly phenols found in most all plants. I’m not sure what the plants use them for, but I’m sure they have a purpose. This is not a horticulture lesson, it is about painting in Atlanta.
How to prevent tannin bleed when painting new wood:
1) You must prime any new wood that you paint, or else you are asking for unsightly tannin bleed.
2) The primer which you use is also very important. I do NOT recommend using a waterborne primer. Although, many say that they work for new wood, I have seen them fail numerous times. Use either an alkyd primer or a shellac based primer. Examples of alkyd primers wood primers are SW A-100 exterior oil wood primer or Zinsser’s Coverstain. Both of these products work very well, especially the A-100. If you want to use a shellac based primer, I like Zinsser’s BIN primer. It is a true shellac and has always fixed even the most stubborn tannin bleed.
3) Either prime the entire piece of wood or spot prime the knots, as they are the most prone to bleed. GreenWave Solutions primes the entire piece of wood because this yields the best Atlanta painting.
4) Wait for the primer to dry, per the label, and top coat the wood. This should prevent any tannin bleed on you newly painted wood.
5) If you have previously painted wood where the tannin bleed has already occurred, spot prime the areas that are bleeding and repaint them.