Painting is the one thing that we have all done. Everyone has painted something. So we all have expectations of the paint we buy. Normally paints are thicker when wet and thinner when dry. That's because normal paints are dissolved in a solvent, whether white spirits or water. When the solvent evaporates, the paint dries. Drying oils, like linseed oil, harden as carbon atoms in the oil molecules bind to other carbon atoms. Part of this drying/hardening process is the capture of oxygen atoms. So the oil actually becomes heavier and thicker as it dries not thinner. So there is the first strange fact about painting with linseed oil paint that you probably didn't need.
The drying metals in our oil act as a catalyst for this absorption of oxygen. Alas, they work so well that the paint surface, exposed to the air, hardens much quicker than the oil below it. As the oil underneath manages to capture oxygen the surface film get larger and, with no where to go, starts to buckle and fold upwards. The result is some fantastically convoluted, i.e. wrinkly, surfaces. So the paint has to be applied very thinly. This is not as easy as it may sound, because the paint is also thin and runny. So it tends to pool. And this is precisely where the paint will wrinkle badly. We recommend that you go back over painted surfaces with a wiped clean brush thinning any areas where paint has collected some fifteen minutes after initially painting it. Doing it again after, say, an hour is not a bad idea.
The painting regime
On new, raw wood, we recommend a first coat of boiled linseed oil thinned with turpentine if you are mixing it yourself. We supply an alternative as a pre-treatment oil. The intention is to saturate the wood as much as possible with the oil, reducing its ability to absorb moisture and thus reducing fungal attack. Raw oil will penetrate more deeply than our paint because it has been oxidised, and the solvent penetrates even deeper, pulling some of the oil in with it. Any excess oil applied on this first coat should be wiped off if you use raw linseed oil, for it takes a long time to dry. Our pre-treatment oil usually doesn't need to be wiped off.Then comes a coat of paint, applied thinly. Dark colours will look good even after only one coat. Light colours will probably look a bit feeble.
Most websites trying to sell you linseed oil paint quote 24 hours before recoating. The non-commercial sites sometimes say 4 days and one site says a week. We find that raw linseed oil can take months to harden. Given that Scandinavian academic reports on the viability of the industry underline the long drying time as the main reason why linseed oil paints are not suited to the modern building industry, the 24-hour claim by Swedish manufacturers seems overly optimistic. But let's face it, if repainting could begin exactly one day later, linseed oil paints would have no significant disadvantages over the traditional gloss oils that are overcoatable in 12 hours. How many people apply the first coat at 10.00am and are desperate to apply coat two at 10.00pm? Only when a day or two off is required between coats, it begins to get very complicated to organise a workforce and their timetable.
On a fine day, our own linseed oil paint really does dry in 24 hours if not 12. Indeed, it can be touch dry in 8. But painting a second coat straight away is not necessarily a good idea. The sooner
Here, you can call it quits. If you wish to add a final coat, this need not be our linseed oil paint. If you are painting something that can remain tacky for some time without that causing a nuisance, the final coat could be linseed oil that you buy from a shop. It could be the left-overs of our paint mixed with left-over pre-treatment oil mixed with some linseed oil from the shop. And it need not be applied straight away. You could wait half a dozen years. Scandinavian researchers ascribe the occasional premature (within fifteen years) failure of modern linseed paint to the quantity and nature of the added pigments. So a final coat with more oil and less pigment is good.
That's a lot of painting, which is why we suggest a final coat that is thinned with linseed oil bought at any diy centre and most hardware shops, padding out your expensive paint and allowing you to use up every drop.