What do glue, paint, tablets and clag have in common?

Another fascinating snippet from the Gippsland Murray Goulburn newsletter:

“Casein accounts for about 80 per cent of the total protein in skim milk post the separation process. It is mostly associated with cheese-making but is harvested from the curd to be used in many products, including glue, pharmaceutical tablets and some paints. Many of us may remember Clag in artwork made from casein.”