Linseed oil or walnut oil? Linseed oil has always been more widely used, but walnut oil has its defenders–sometimes passionate defenders. Leonardo was one such.
Walnut oil yellows less than linseed oil, but it’s relative. I suspect the difference affects poor quality versions of the oils, with low quality linseed yellowing more than poor quality walnut. Today there are plenty of good quality oils and this issue is not so important. Of course, some purists will disagree.
My preference is linseed oil but lately I’ve been testing, that is, using, walnut oil. I’ve substituted walnut oil for linseed in my usual medium. My medium, for those who are curious, is 1 part turp; 1 part drying oil; 1 part copal-oil varnish (1:1 with turp); plus a drop of dryer. Paint can’t dry too soon, as far as I’m concerned.
Walnut oil is firmer than linseed and covers a little better. The difference isn’t strong but it’s definitely there. The extra firmness means it takes more effort to manipulate the paint; again, not much of a difference but the effect is noticeable.
Linseed is more malleable which means it performs a little better. This is hugely important to me. But linseed oil, due to its transparency, doesn’t cover as well as walnut. If you use a lot of glazes (I don’t), linseed is a better option. But if you’re trying to cover something, linseed requires more effort. For a covering linseed oil, I add a drop of stand oil to the medium, so it’s not an issue.
These differences are relative.
I still prefer linseed oil. But I’ve upgraded my judgement of walnut oil. I wouldn’t lose any sleep if I could only use walnut oil for the rest of my career.