"White glue" is an aqueous dispersion of polyvinyl acetate. I have found that an inexpensive gouache paint can be made by blending finely-sieved chalk paint with the school glue. The paint increases in color value when dried, as expected with gouache. A sample of dried paint will slowly lose adherence to the paper surface as expected with gouache. Paintings with gouache can be protected by rubbing the work with 'cold wax'. Particles of chalk can be brushed off when the paint dries or left in place. A finer sieving can also be considered before use. I added a few drops of commercial Evonik dispersant , but I saw no advantage. Color value can be built up with application of successive layers with a wet brush, as usual with gouache.