Welcome to the last installment of our Interior Paint Problems and Solutions series. This installment focussed on surfacant leaching and tanning.
Concentration of water-soluble ingredients on latex paint, creating a blotchy, sometimes glossy appearance, often with a tan or brownish cast.
Many different water-soluble materials are used in the manufacture of latex emulsion paints. When these paints are applied during hot and humid periods and dry during cool evenings, the painted surface will cool, allowing dew to form. This accumulated moisture on a paint surface whose curing is temporarily delayed may extract and concentrate different water-soluble materials from within the paint at the paint surface. As the water evaporates, a concentrated residue is left behind, causing staining, unsightly runs and gloss patterns.
Aluminum siding will react to temperature changes faster than solid vinyl or wood siding because of the smaller amount of material involved. Consequently, aluminum siding will develop surfactant leaching quicker and more easily; however, all siding including masonry is prone to this problem under identical conditions.
Use of lower quality paint.
Apply paint to all surfaces during weather conditions that allow proper curing of the paint film. When “surfactant leaching” occurs, flush with clean water immediately before the stains have sufficient time to set up or harden. Light scrubbing with a soft brush is acceptable. If stains cannot be removed in this manner, then repainting will be necessary during more favorable weather conditions.
Brownish or tan discoloration on the paint surface due to migration of tannins from the substrate through the paint film. Typically occurs on “staining woods,” such as redwood, cedar and mahogany, or over painted knots in certain other wood species. However, tannin staining can occur with any kind of wood.
All woods, but especially red-colored woods, contain a water soluble dye called tannin. Tannin is not soluble in most solvents. Application of latex topcoats directly to these red-colored woods may develop a red-colored stain on the finish coat. If the dry film is intact and discoloration occurs at a later date, then staining is being caused by water moisture within the board wall. This moisture will migrate and eventually carry staining substances from within the wood to the surface of the paint film.
Some cedar woods contain colored dyes such as tannin which is water soluble, and other colored extracts which are soluble in mineral spirits. In these instances, a primer that has discolored should be spot tested with a second coat of primer or a latex topcoat to determine which will successfully block future discoloration.
If dry film is intact and discoloration is occurring at a later date, then internal moisture is the culprit. The moisture source must be located and corrected. Remove stains by washing with a solution of equal parts alcohol and water. Allow to dry thoroughly.
New red-colored woods must be sealed with an oil primer that will function as a barrier coat, preventing staining of the topcoat.
Note: Even with proper preparation and recommended products, tannin bleed can still occur (especially on new woods) with both latex and oil topcoats.
We hope you have enjoyed and possibly learned a few things with our Paint problems and solution series. We will be posting articles on a monthly basis. Some months may have one or more articles so make sure you keep following us for more tips and solutions!