Technical Tip by "Vince Palmare"

Wood Mold and Mildew


mildew mold

Examples of Mold Growth on Logs

Mold and mildew are terms that are used interchangeably since they refer to the same living organisms.  For simplicity we'll refer to them as molds.  Molds encompass a wide range of fungal species that can live on the surface most materials, including wood.  They require air, water and food.  Their color is usually white or black but can be just about any color.  If the growth is green, it's probably algae.

The molds that concern us live on wood fibers or even on finished surfaces. Bare green wood is very susceptible to mold growth since the high moisture content provides lots of available water and the wood's nutrients are readily available as food.  Many types of mold grow on green wood.  They vary from black spots to white tendrils (commonly called dog hair).  All mold growth MUST be removed before any of our LIFELINE finishes are applied.  While it may not be clearly spelled out on our labels, our instructions and timelines are intended to provide you with the best knowledge that we have about preventing the growth of staining molds underneath our finishes without having to use potentially toxic and caustic cleaning chemicals.

It is fairly easy to remove mold from bare wood surfaces.  Cleaning products like Wood ReNew and Log Wash do an excellent job.  Many companies recommend bleach and water solutions but we know that caustic bleach solutions destroy wood fibers and create iron tannate stains. So, we looked for cleaners that would work without bleach's damaging effect on wood. One result of that effort was Log Wash, a low pH cleaner that is compatible with woods natural chemistry.

All of our exterior stains and topcoats contain mildewcides that help prevent the growth of mold on the surface of the finish. They do not prevent the growth of mold on the substrate under the finish. That's why its so important to thoroughly clean the surface prior to applying the first coat of stain or primer.  Mold spots forming under a finish is an indication that the surface was not properly cleaned during preparation. The only way to remove them is to strip the finish down to bare wood to get at the mold.

Occasionally shaded, warm, moist environments can create conditions so conducive to mold growth that they can overcome the mildewcide additives contained in the finish.  One way to handle this type of situation is to thoroughly clean the walls with Log Wash and then apply a coat of Advance Clear Topcoat mixed with Stay-Clean additive.  Just be aware that the addition of Stay Clean will diminish the glossiness of Advance Gloss.

A final thought about maintenance of exterior finishes.  When you apply a maintenance coat of LIFELINE Advance, you are renewing the water repellants, the UV inhibitors and the mildewcides on your exterior walls.   Maintenance of that exterior clear coat has many important functions that protect the wood and maintain the appearance of the house, including making it easy to keep clean and free of mold.


"Vince Palmare"


Last modified on Wednesday, 08 January 2020 14:55

Related items (by tag)