This was done on 6 x 6 black gessoed masonite. I went to Home Depot and got some 4'x4' masonite sheets. My terrific neighbor cut them into different sizes for me. I have a lot of sanding edges and gessoing to do. I did enjoy working on this black panel. I might even try some different colors. Mike Rooney said in a blog that it is safe to use acrylic as an underpainting for oil.