There is a general perception that when using linseed oil paint, the surface must be new, untreated wood, or that all old paint residues must be removed. This notion is both right and wrong.
Substrates for Acrylate and Alkyd paints
First, you must remove all old paint that is loose. A paint scraper is often used for this purpose. It soon becomes clear that some old paint releases easily, but in other areas it will not budge. The question arises: Does all the paint have to be scraped off?
Before making a decision, think about whether you have the resources and energy to clean the substrate completely. Linseed oil paint adheres extremely well to various surfaces, thanks to the oil’s small molecules and penetration ability. In most cases, repainting over old, hard-wearing paint that is not linseed oil paint works quite well. You do not conjure away the old paint by painting over it, and the linseed oil cannot penetrate the wood, but that may not always be necessary. Exposure to sunnier, windier weather – to the south and west – degrades paint surfaces more, requiring more frequent maintenance. For north-facing surfaces, you can be a little more “casual” and sometimes skip repainting. Washing the surface may be sufficient.
However, those who want to be 100% certain should remove all old acrylate or alkyd paint before repainting with linseed oil paint.
Substrates, old linseed oil paint
When painting a surface that was previously painted with linseed oil paint, you do not need to scrape off the old linseed oil paint. Just scrape off any loose paint. Wood painted with linseed oil paint is usually saturated with linseed oil, so you do not need to prime the wood again. Priming may make the surface too oily, and the next coat may not adhere well. If you are unsure of the status of the wood, you can do a test. Apply a little raw linseed oil to a 2-foot square area of the surface to be repainted. Wait 30 minutes. If the linseed oil has been absorbed into the substrate, it may be necessary to prime. If the oil has not been absorbed and the surface is still glossy, no primer is needed. Do this test on all sides of the building. You will get different results. The south side may require a basic coat of primer, but the north side may not. You do not need to paint the same number of coats on all walls. It’s logical, really. More exposure to the sun breaks down linseed oil faster, and these surfaces require more maintenance than those with less sun. When repainting is completed, all facade surfaces should have the same gloss.
Substrates, Calcimine paint
You can paint over calcimine paint with linseed oil paint, but not the other way around. Brush or wash off most of the calcimine paint and start with a primer, followed by an intermediate and a final coat. The single-coat color method can also be used, but in that case, choose a color as dark or darker than the existing calcimine color.
General work instructions for repainting
Always wash facade surfaces with algae/mold cleaner (the Biokleen Algae/Mold Wash product is available in our line). Be sure to rinse off all detergent with water. Then scrape off any loose paint.
If the cleaned surface is heavily absorbent, mix a primer according to the instructions found under “Painting on wood, exteriors” and paint three coats: Primer-Intermediate-Final.
If the surface is “semi-oily”, you can mix a leaner base color, for example 60% paint, 20% raw linseed oil, 20% gum turpentine. If the surface is oily and saturated with old linseed oil, you do not need to prime. In this case, paint only two coats: Intermediate coat + Final coat.
Silicone, wax, and tar cannot be painted over
Materials and surfaces that contain silicone and wax cannot be painted on. The paint will split and peel away from the substrate. If you paint on tar, the tar can bleed through and discolor the linseed oil paint.