Re: Casein Opacity?
When working in thin glazes, they can be layered after becoming touch dry, but like watercolor are easily reactivated so one has to apply those carefully and not scrub the next layer in.
I consider a painting or layer as cured in about a week or two (depending on your humidity levels and ambient temperature), this can sound like a long time to wait between layers, but is easily solved by having multiple paintings going at one time. After a week of summer here in the east US with minimal rain, my Casein work is usually ready to be buffed without much, if any, color coming off but becoming quite glossy after the buffing. I have a test page available from a few years ago that is not fully buffed, I will see if I can find it and snap a pic then buff it and get another to see the difference in color. Unfortunately it was intended to be a thick and direct application of color, so I cannot show off the transparency effects very well... maybe a bit of the lighter colors over the darker will show it though. Be back with it in a couple days (it is in storage).