Bonnie, Thanks for your great answer which I would never have figured out myself. Yes, I did flip it and slump with the glossy side down. I often flip my pieces but I think they are usually slumped in gently-sloped molds, like the 10" ball surface mold. I will try re-flattening it. Can you give me a kiln program for doing it; I don't understand your suggestion. The piece is 3/8" thick, on-edge strip construction, 8" square. Thanks again.