This year I resolved to learn oil painting. Although I have dabbled in most media, I have never tried oil painting because it's "too expensive" and it's something that only "real artists" use. That's a pretty silly thing to think, right? So for Christmas I bought myself a beginner's oil painting set, and a very well-reviewed book about learning oil painting.
Non-toxic is good!
Not knowing better, I bought traditional oil paints. Whereas the beginner's oil painting book strongly advocated using water-soluble oil paints. I didn't even know there was such a thing, and I was a little dismayed to learn that I was already behind the curve when it came to art supplies.
To a beginner, the issue of solvents is a confusing one. Oil painting involves so many different chemicals, with overlapping uses, and a seemingly endless list of substitutions. For example, I bought a tin of Turpenoid Natural, which is a turpentine replacement that is non-toxic and has a pleasant citrusy smell. However, it turns out that this is only effective as a brush cleaner. The manufacturers recommend that you do NOT use it to thin your paints, as you would with traditional turpentine.
It should also be mentioned that you don't really NEED turpentine in the process of painting. Turpentine is used to thin out the paints, which you would mainly do if you wanted to create a thin glaze. If you paint in an impasto style, or alla prima (without using a second layer of glazes), you could probably get away without ever thinning your paint.
There are many oils that you can use to change your paint's consistency. They don't thin the paint the same way that turpentine does, but they might get you close enough to work. Linseed oil, walnut oil, and alkyd medium can all be used by many people without having a reaction. (Although they are not entirely non-toxic, they don't have the same issue with toxic fumes as turpentine.)
Many fine artists use water-soluble oils successfully. Others find that they feel like they are wrestling with the paints. And I suspect that a lot of artists might be interested in switching, but aren't willing to sink that much money into replacing all of their paints at once.
One undisputed use of water-soluble oil paints is for the traveling artist. Because airlines forbid you from bringing flammable and toxic substances on the plane, a travel kit of water-soluble oil paints would be just the thing!