Acrylic or Casein?

A few weeks back while discussing casein paint, someone asked, "why not just use acrylics?'

"Racing," 4x6, casein on panel

Why not indeed? After all, acrylics are water-thinned, dry very quickly, are widely available in good grades and many hues, and have the virtue of extensive experience among a wide range of artists. Acrylics have proven themselves as a plastic, easily-handled medium. You can paint thin and transparent or more thickly, like oil paint. The paint layers are flexible, probably very long-lasting and generally light-durable too. Many favor acrylic paint as a substitute for oils.

But casein has a lot of virtues too. Casein paint dries very quickly,

"The Silver Creamer," 4x6, casein on panel

allowing the artist to work at least as quickly as with acrylics. Casein is a water-based paint too, allowing thin and thick application. Casein dries matte, which allows for great photographs, so that in the middle 20th century (before acrylics) casein was the go-to choice for many illustrators. Casein dries to a more rigid film, so firm supports are necessary (wood, bristol board, etc.) but otherwise the paint is very durable, so durable in fact it is one of the most ancient kinds of paint man has invented. Unfortunately, casein paint is only made by a handful of companies worldwide. Casein is a bit like gouache but unlike gouache, once casein has dried it isn't dissolved by water.  One final point: casein is made from milk protein and is therefore a renewable item; acrylics are made from petroleum.

So how to choose? Why not try a few tubes of casein paint and see?