Linseed oil is used as a carrier in many brands of paints and stains. Since linseed oil is organic, many varieties of mold fungi thrive on it and over time they can proliferate to point where the coated surface can turn dark brown to black. One way to tell if the darkening is due to mold rather than UV damage is that those exposed areas protected from direct sunlight under eaves and overhangs will be the same dark color as the rest of the wall.
When this occurs, washing with Log Wash™ alone will not be enough to remove all of the discoloration due to mold growth. We recommend to first use Wood ReNew™ along with some scrubbing in order to remove the visible mold. Once the surface is cleaned with Wood ReNew, use Log Wash to help remove any residual linseed oil that may still present.
Media blasting alone is not a satisfactory method of removing a heavy growth of mold. Linseed oil penetrates into the wood and although blasting may remove most of the surface discoloration, there may be enough residual linseed oil remaining in the wood to support mold growth underneath the finish. If the home has been blasted, it will be necessary to give the home a good washing with a Log Wash solution (2 cups per gallon of clean water) before applying Prelude™.
The best way to prevent this problem from reoccurring is to avoid the use of any product that contains linseed oil. None of our Lifeline™ finishes contain linseed or other types of organic, naturally derived oils.