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Discover Tannin with Zetagi

What is tannin? What causes it? Why does it occur? How do we prevent it using Zetagi by Sparko products?


Tannin is the tan or brownish discoloration found in many wood species. Tannins can bleed through the painted or coated surface, leaving a yellowish-brown stain which is usually perceived as paint yellowing especially in white or light-colored paints/coatings.


  1. Improper surface preparation or failure to adequately prime and seal the surface before coating.

  2. Humidity or other moisture problems causing tannin to rise on the wood surface.

  3. Using a sealer and topcoat that is non-tannin stain resistant.

How to deal with it:

  1. Internal moisture is usually the cause of tannin discoloration. The moisture source must be located and corrected.

  2. Allow the surface to dry thoroughly. Check to be sure that water will not affect the adhesion of the coatings.

  3. If you are working with an old wood table or furniture make sure to remove all loose paint with a scraper or wire brush. In some cases washing it with Sparko 604B PU Thinner to ensure that the furniture is “washed”.

  4. Let it dry at room temperature for about 30 – 60 minutes.

  5. Seal the surface or stains with a coating that is designed to trap those tannins.

  6. To correct or resolve tannin issues use Zetagi Non-Tannin sealer White and Topcoat. Zetagi Polyurethane Wood Coating inhibits the release of natural tannin of wood thereby preventing the yellowing of the finish.

Always remember tannin secretion is a surface problem and still can occur even with the proper preparation especially on new wood. To prevent these tannin problems make sure to use the recommended products from Zetagi by Sparko Surface Coatings.

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