Hello! I’m new, so let me know if this should be in a different forum.

A friend would like to commission me to repair and prevent cracks in two framed paintings done using the cheap “tempera” paint that grade schools use. They were done on canvas board by pigs on a rescue farm: the paints are put on canvas board, covered with plastic wrap, and then the pigs push the paint around with their snouts.

The cracks are, of course, almost entirely in places where the paint was applied thickly. (I like the look of the cracks, but I couldn’t convince my friend!)

The repairs are straightforward enough, but is there any way to prevent further cracks? Like, go over it with egg yolk? Or some sort of varnish I could apply? Any ideas at all are welcome!