I am developing casein paint formulations that can extract azo dyes produced by the "grind method".
I will upload images as I proceed with my research. The casein is contacted with calcium hydroxide or calcium carbonate. As the paint ages, I will follow any changes by FT/IR and value changes in the dried paint. Chitosan is an interesting additive to the binder, for example.
We respect tradition by continuing to study this paint and minimize use of acrlyics, alkyd resins, polyurethanes, etc.
In this image: a rapidly drying swatch ( acrylic paper ) where I dip brush in the paint binder and apply to an inexpensive watercolor pan set. Of course, the brush must be cleaned in water quickly before the paint dries. The surface of the swatch is reasonably waterproof in 15 minutes.
The cave artists used casein binder and it has stood the test of time.