oil painter here..... basic linseed oil takes ~70 years to cure properly. pure linseed does, in time, a nice hard firm. there are a number of plant oils for p

oil painter here..... basic linseed oil takes ~70 years to cure properly. pure linseed does, in time, a nice hard firm. there are a number of plant oils for painting (saffron, sunflower, walnut, linseed, poppy: different dry rates and hardness rates), and there are a number of ways for treating them. Specifically we usually avoid plain boiled linseed oil, as it tends to yellow. That is, I believe, the common hardware store oil paint. fundamentally - artist oils are engineered for divergent purposes than house oils. resins are hugely variant - artists are usually suspicious of things that aren't engineered & tested to last > 50 years, so house painting probably has a much larger variety. the pigments affect the oil dramatically. quinacridone pigments stay wet for days, if not weeks, whereas umbers (due to the manganese) will dry within 24 hours. with respect to varnishes, that's not how oil painting artists think of varnishes: a traditional varnish is dammar resin dissolved into (pure) gum spirits of turpentine, laid on about 6 months after the painting is touch-dry. Today we typically use a acrylic varnish with a UV protectant, i.e, what's sold under the trade name "Gamvar". Such modern varnishes are designed to not link against the oil and permit stripping and reapplying to use as a protective layer. it's technically correct to call oil paint colored glue, I think. But it's not useful to think of it that way. I think of it as "oily mud applied with a hairy stick" when I feel reductionist. I love talking about artist oil paints, happy to answer any other questions.