Waterlox products do not contain any mold or mildew killing/controlling additives. If you are using our finishes in mildew prone areas (dark and damp), you may want to consider some mold/mildew prevention steps. Notable areas of concern would be some porch ceilings, exposed but shady areas on outdoor surfaces, underside of outdoor furniture, etc.
Starting a New ProjectPre-treating the Raw Wood
When finishing an existing surface where mold/mildew is a concern, it is best to pre-treat the surface before finishing to kill any existing infestations. There are quite a few options available on the market that are usually borate-based products and can be liquids or powders that are usually mixed with water and applied with a simple pump sprayer. Most of these products need to be applied to completely unfinished wood to allow the product to penetrate. Read all directions carefully about dry times and when coatings can be applied. This will do well to prevent any mold or mildew development underneath film if water does find its way into the wood. It is very difficult to fully seal a piece of wood, especially if it was preassembled before finishing, so water may be able to find its way under a coating.
Read the label and instructions carefully and make sure you are using the correct product to deal with the issue. Some products are better suited for preventative care of new wood, while others may be more suited to eliminate current issues as well as treat the wood.
To prevent mold/mildew on your finished surface, you can also add paint additives to your final coat of finish. There are many stir-in products available at local hardware stores that are usable in paints, stains, sealers, etc. but read the label and make sure it is compatible with the product you are using (most Waterlox products are oil-based).
Adding additives to the paint will help protect the coating from mold/mildew growth, but it will do little to protect the wood underneath if there is already a problem. Because it will usually grow on the surface, the additive is usually only needed in the final coat. If you are adding these products to surfaces that may see food contact, read the label carefully and ensure that it would be safe to use around food.
Mold/Mildew on a Waterlox Finished Surface
If you have already completed your project and you’ve noticed mold/mildew growth on your surface, it can be cleaned with a solution of 5% bleach and water solution. Do NOT use anything above a 10% bleach and water solution, as that will damage the finish. Do not saturate the area with the bleach solution. Wipe the mold/mildew to kill and remove the damage and IMMEDIATELY rinse with clean water to remove any bleach from the surface. Recoating may not be needed at this time, but it is recommended to apply a fresh coat using a paint additive as described above to help prevent future problems. For particularly stubborn spots, lightly sand with 320 grit paper and mineral spirits AFTER treating with bleach to kill the mold/mildew and not kick up particulates. Follow any sanding with a recoat.