Lean egg tempera grassa prpared using egg yolk, white and commerical 'Murphy Oil Soap'. I shake the yolk and white 2 minutes, add one eggshell full of the commercial Murphy product and shake ten minutes yielding a stable emulsion. I add one part of a commercial watercolor paint to one part of the emulsion. It dries quickly and flows off the brush quickly on bristol paper.
I am a chemist and an artist. I will be examining the use of dried egg yolk which can be re-constituted before painting. Artists know that classic tempera paint has a short shelf life before use.
I will post our results here in a few days.