Casein paint has been used since ancient Egyptian times. This water-based paint is durable, quick drying, with the pigment binder being casein – a protein derived from milk. Yes, milk! It is often referred to as “milk paint”. Who knew? Casein paint dries very fast to a matte finish. Although it can be re-wet and worked within a few hours after it dries, it becomes very permanent and water-resistant after a few days. Once dry it can be varnished like oil and framed without glass.
Casein is a bit difficult to find in local art supply stores, but can be ordered online here: https://www.dickblick.com/products/shiva-casein-colors/
If you are an oil painter, this may be a nice break from oils, allowing for more versatility in your range of painting techniques.
