Originally Posted by
resource fabricologist
Put it in the sun again on a flat surface and place a piece of glass on top to hold it flat.
Now that would result in one nasty accident. It was on concrete---------the only concrete we own, a bit of sidewalk in front of the kitchen door porch. I brought it in after the sun went down, so it had cooled a bit. Washed it off in the bathtub and stood it on its side in a tight spot so it doesn't warp again.