An interesting link, Margo, but for a warped mat, by the time we purchase "heavy plate glass" and get it finished off so we don't cut the daylights out of ourselves, we might as well just get a new mat. I warped one once by leaving it on the backseat of my car and it was a sick feeling when I discovered it. Thank goodness for Joann's 50 percent off coupons once in awhile.