MITRA Forum Question Details

In general, I would suggest a traditional chalk-glue ground or traditional true gesso (Gypsum in animal glue) ground on a stable and rigid support. While the addition of oil is often though to allow for a wider range of ground but especially substrates but my experience has been that unless the oil component is exceedingly high (and even then this is really no guarantee) it is still best thought of as a paint requiring a rigid support with an absorbent ground. I have not read any reliable reports, and certainly no comprehensive studies, to show that these mixed, emulsion media are appropriate for supports that are more flexible. Much of the early 20th century experimentation with these mixed emulsions; especially on flexible supports have had rather disastrous results.

Of course, a ground with a similar proportion of protein and oil would also be appropriate. I would expect that a half-chalk ground (an oil and glue emulsion ground) would likely be perfectly appropriate for such a paint medium.

Honestly, I would even suspect that a lean acrylic dispersion ground on a rigid substrate would likely be fine but this is one of areas where I am not sure if enough work has been done to determine the long-term longevity of such systems. I will send out a few feelers around to see if there is any data on this issue.

​We don't have older tempera grassa samples that would allow us to determine long-term stability of these films on acrylic dispersion grounds. But I found time to apply some tempera grassa recipes on: GOLDEN Gesso, Black Gesso, Absorbent Ground, Pastel Ground and traditional chalk-glue ground. The tempera grassa consisted of yellow ochre pigment, egg yolk, stand oil and various amounts of water, and in one case OMS instead of water. Between the recipes there were no differences noticeable on the various ground. All emulsions worked best on the chalk-glue ground. On the acrylic grounds subsequent paint layers lifted when brushing over the same spot more than 4-5 times. Of the acrylic grounds the Absorbent Ground seemed to take the emulsion paint the best and paint lift was the least.