To follow up on my previous post, I had found that one of my Richeson/Shiva paints, Cadmium Green, transferred to a dry paper towel with just some light rubbing after the paint had dried. Now I wanted to see if other tubes I owned had this same problem. They do.
This picture shows a sheet of paper on which I painted 1 inch swatches of all the different tubes of Shiva paints I have. The paper towel at the bottom shows pigment from each swatch that transferred over. I did not dilute the paint at all with water, and did not apply the paint too thickly. All of the paints smeared easily when rubbed, some more than others, with the sole exception of the Raw Sienna. The ivory black in particular smeared very badly, and even after a day of drying felt to have a weak paint film.
Since all of the paints are old, in some cases decades old, I asked around to other people who used these paints if they could test any tubes they might have that are newer, and see if they had the same problem. I heard back from a couple people. One person had some Richeson caseins that were only months old, and found they had the exact same pigment transfer problem. The other artist rubbed the surface of paintings he had made that were at least 3 months old, and said no paint at all rubbed off. What this tells me is it might be possible that if the paint is allowed to cure for awhile longer, the pigment will adhere better and not rub off. This strikes me as a strong possibility. So, I think I’ll do a new test on paint swatches that sat undisturbed for a month or more, and then see if any pigment rubs off.