an insomniac misanthrope who enjoys cooking, textile arts, farming and eating delicious food.
A traditional, inexpensive way to extend and thicken paint is to use marble dust, a.k.a. calcium carbonate. This should aid drying. I haven’t really noticed a leveling effect on the brushstrokes — but then again, I tend to paint thin
Lately, I’ve just been mixing up some loose calcium carbonate powder with some of Art Treehouse’s water-washed linseed oil right on my palette to make the putty material that Tad Spurgeon writes extensively about on his blog (https://www.tadspurgeon.com/content.php?page=putty+tutorial). I’m pretty happy with this, as it’s easy to control the consistency, and it seems to make sense to mix only the amounts one needs for that session.
Regarding the putty, note that I’m not certain what sort of difference it might make to use artist’s refined linseed oil in place of the water-washed oil he recommends. Also, I understand that one should use a mask when working with calcium carbonate powder as it can be a respiratory irritant.
That is all there is to it – mix the powder into some oil until you get the texture you want. Test it by mixing into your paint and adjust the amounts as needed.
Limestone powder is a type of calcium carbonate as are chalk and marble dust. The grit size of the powders used will influence how they react in the oil. I prefer the way fumed silica behaves in an oil gel vs the calcium carbonate paste like materials. You can make your own silica gel as well by adding fumed silica to linseed or walnut oil, or you could try both to see what happens. As already noted, wear a mask when working with powdered materials. Fumed Silica will float in the air with the slightest bit of air movement so take precautions.
Back to your question – Calcium Carbonate added in ends up making a more self leveling putty than a gel for me no matter what I mix it with. ...
...
There might be an issue adding only more solids (the calcium carbonate) to your paint since the paint is already going to be at the max binder to pigment ratio, so I would be adding the filler to some other liquid such as linseed oil or the medium rather than to just the paint.