Canvas white pigment and calcium carbonate is rather brittle and susceptible to cracking. As lead-based paint is poisonous, care has to be taken in using it. Various alternative and more flexible canvas primers are commercially available, the most popular being a synthetic latex paint composed of titanium dioxide and calcium carbonate, bound with a thermo-plastic emulsion. Many artists have painted onto unprimed canvas, such as Jackson Pollock, Kenneth Noland, Francis Bacon, Helen Frankenthaler, Dan Christensen, Larry Zox, Ronnie Landfield, Color Field painters, Lyrical Abstractionists and others. Staining acrylic paint into the fabric of cotton duck canvas was more benign and less
Canvas damaging to the fabric of the canvas than the use of oil paint. In 1970 artist Helen Frankenthaler commented about her use of staining: "When I first started doing the stain paintings, I left large areas of canvas unpainted, I think, because the canvas itself acted as forcefully and as positively as paint or line or color. In other words, the very ground was part of the medium, so that instead of thinking of it as background or negative space or an empty spot, that area did not need paint because it had paint next to it. The thing was