I use anything cotton, no polyester. I hate the foam bonded covers because you cannot wash them. I have kept layers of cotton batting, folded sheets that were worn out (cut to shape)etc on my board, and I make my own cotton covers because I want to launder them. If they get a build up of starch or slight scorch, it can stain other clothes or fabric if you mist them (which I always do), so my covers get laundered and rotated frequently. My total padding is about 1/2 inch.
