All About Linseed Oil

All About Linseed Oil - And Why It's No Good For Wood

We occasionally get calls about the exterior of a home that has turned black.

Almost without fail it's the result of using an oil-based stain that contained linseed oil.


Linseed oil is a yellowish oil derived from the dried seeds of flax plants, and is also known as flax seed oil. Linseed oil is used as a carrier in many brands of oil-based paints and stains. Since linseed oil is organic, many varieties of mold fungi thrive on it. Over time mold 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 inspecting areas protected from direct sunlight like under eaves and overhangs; it will be the same dark color as the rest of the wall.

When this occurs, washing with Log Wash alone may 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.


We don't recommend blasting alone as a 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 under the finish. If the home has been blasted, it will be necessary to give the home a good washing with a two cups of Log Wash per gallon of water solution before applying Prelude.

The best way to prevent this problem is to avoid the use of any product that contains linseed oil. No Perma-Chink Systems finishes contain linseed or other types of organic oils.

For more information, read these technical tips:
Cleaning with Wood ReNew and Log Wash Technical Tip
Why we recommend (and produce) water-based products

Last modified on Thursday, 28 September 2017 23:13