What's better on rock paintings?

It's better to paint rock colors on linen. Flax is small in water absorption, shrinkage and expansion, and it is not easy to sag and deform after stretching and brushing alum water on the picture frame to dry. Rock color is a kind of pigment, which is different from the pigment generally referred to in traditional art knowledge. It has a clear and unique aesthetic feeling of materials, which can be called colored materials or, more professionally, rough materials with tones. Rock color is different from glossy oil paint, watercolor and acrylic color that can be diluted with water. It is heavy to hold in your hand, and it is gray and elegant to draw on the screen.