Definition:(noun) - Stain Painting is a method that allows the oil or acrylic paint to seep into the fiber of an unprimed canvas. Helen Frankenthaler and Morris Louis are best known for using this technique. In Frankenthaler's case, the artist used a squeegee. Louis was quite secretive about his method. Frankenthaler claims that she invented Stain Painting. Others claim that Louis was first. It's up to you to decide.