Cheap materials for priming / underpainting

Flame Boy asks: "I paint in gouache and I don’t have either acryla gouache or casein to prime with and a very limited budget. I have watched a fair share of your videos and you always seem to prime your canvas. Is it possible for me to reach a similar result to you without priming beforehand?'
Answer: Yes, you don't have to always prime your surface. You can paint right on the white paper or board. Or you can just get a couple tubes of acrylic (say Venetian red and Ultra blue) to tint your gesso or your acrylic matte medium. Acrylic gesso is pretty cheap. You could even prime your surface with a matte acrylic house paint. If you want to build up some impasto-like texture and you're working on a board, you can use modeling paste.

Steve asks: "How do you keep gouache from cracking and flaking?"

A: Here are some suggestions: Use rigid board, not paper. If you have thick gouache on thin, flexible paper, flexing the surface will cause it to crack or flake off. The surface should be matte & absorbent, not shiny. A glossy surface is less receptive for later layers to adhere to. Be sure not to use oil priming under any water media. Avoid impastos in paints like gouache or casein which have a weak emulsion strength. If you want the thick-paint impasto look, you can prime with modeling paste or other acrylic texturing which dries with a tough glue-like emulsion. As always, experiment first.

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