How can you take a warp out of a LP?

I have never tried this myself: however I once read about a way this could be done. Basically, sandwich the disc between two sheets of heavy plate glass and let it sit in sunlight for a bit. The sunlight warms the disc up just enough that it becomes a pliable, but no so much that it melts. The weight of the glass presses it flat. Remove it from the heat of the sunlight and let it sit for a while to cool down and set in its new flat shape. It would seem to me that this might also work with thinner glass and some clamps. Obviously, temperature and time are the two critical variables, but no further information was provided by the person who wrote the suggestion. I don't know if this is ridiculous or if it works; however, if you have an album that is otherwise unplayable, what have you got to lose ?

My recommendation is to buy a VPI turntable with the outer ring clamp and stainless steel center clamp. I've had mine operating for less than a week and I'm amazed at how my warped records (out of thousands of LP's, I do have a about 10-15 badly warped ones) now play perfectly. The clamps make all but the worst warping essentially irrelevant.

I have a JA Mitchell SE Spider and I use the record clamp and it plays ok, but it requires me to lift the tone arm to clear the warp. (about 3/16" high)