I black line a cactus on light green or white construction paper. I mix Liquid Starch, Salt and green tempura.
Children then paint their cactus's.
The surface, when dry is gritty and scratchy. It is a wonderful tactile experience. It is a little messy, but the outcome is really neat. Pre cut different sizes of cactus from white construction paper. The mixture needs to be thick in order to make the salt stay on the cactus when it's done drying.