Re: Casein vs. gum
Agree. I was replying that gum:watercolor=casein:guache, especially if you
use earth pigments.
Can't speak about casein+acrylic but, as I understand it, the binder
itself is not clear(ish) like gum. Therefore I expect to get more opaque
layers with casein (especially so when combined with the potential of
using a lot of pigment) -> quite the opposite of gum. Analogy would be
gouache painting (casein) vs. watercolor painting (gum)... And what I saw
up today (all web representations) seems to support my theory. OTOH, I
could be completely wrong -> I'll see how it goes for me soon.