What Do You Need to Do to Prime Wood for Linseed Paint?

What Do You Need to Do to Prime Wood for Linseed Paint?

Published by Michiel Brouns on 13th May 2021

One of the biggest benefits of linseed paint is how well it protects wood from the elements. This is a huge advantage if you are using it to paint outdoor wooden features such as gates, sheds, fencing, doors or window frames.

The basic science here is simple: the surface tension of linseed oil is lower than that of water. This means that linseed oil will penetrate deeper than water ever will, with no particular effort needed.

Despite this, some people still recommend taking extra steps to make linseed oil penetrate deeper. We’ve spoken to quite a few customers who have been advised to take steps such as soaking timber in oil before painting it, or even heating the oil to make it penetrate deeper.

We absolutely do not recommend doing either of these things!

Soaking timber in oil could result in it losing its shape, or even splitting. Heating the oil is a particularly bad idea, as when the oil cools down it will expand in volume. This increase in volume can result in timber cracking and warping from the inside. This happened on the Haddon Hall Estate, when some gates were dipped in hot oil. Once the oil had cooled, the various timber elements that made up the gates expanded and then simply didn’t fit together any more. Following our advice they no longer follow this method.

There’s another problem with saturating timber with oil before painting – hot or cold ­­­– and that’s the issue of adhesion.

The protective benefits of linseed paint come partly from the oil and partly from the pigment. The best result is achieved when the pigmentation is carried into the timber together with the oil, but this won’t happen properly if the timber has been pre-saturated with oil alone. In these cases, you’re relying on the adhesion of pigment on top of the oil. If anything goes wrong with this process, the finish will fail. We’ve seen this problem following an enquiry from Tatton Hall, where a conservatory was painted this way in the past with a linseed product. The final finish soon began to show small, square cracks as a result. Following the correct procedure this no longer happens.

So what do we recommend? For best results on bare wood, we suggest starting every painting project with a primer coat. This should be mixed using the linseed paint itself. The best formula we’ve found is to mix around 50% paint, 35% linseed oil and 15% balsam turpentine. This thins the paint for the application of the first coat and makes it easier to ensure the paint is fully worked into the timber. These ratios are not set in stone and in some cases, painting straight from the tin is certainly an option – it all depends on the absorption level of the timber.

Essentially, linseed paint is a time-tested product that does an excellent job. The best way to let it do that job is to keep things simple! You can find a full video guide on how to use our exterior range here