How best to eliminate LP warps

As my brain continues to de-fog (thanks all you guys!), I now remember doing A-B comparisons between having the SOTA vacuum hold down on & off. Vacuum hold down gave me more weight and dynamics but I often preferred the lighter, airier sound of just letting the LP lie there on top of the platter. . Imaging was different between hold-down and non-hold-down but were equally satisfying. A screw-down clamp meantime, puts me halfway between with the best of both worlds. In any case, a screw-down clamp is the way I now almost always go.

Thanks, guys.  I think we've covered the waterfront when it comes to curing warps. Unless someone else has a treatment not already mentioned.  My preference is to reduce the magnitude of the warp before playing the defective LP.  I am less interested in clamps and vacuum hold down, in this instance.

Clearaudio outer ring. Wayne’s audio outer ring. Vpi outer ring. Add any center weight. 

Vinyl Flat and Groovy Pouch hasn't failed me yet.

I use two pizza stones. And put the record in-between. You can probably use glas also.

But use uven instead of sun. The sun is unregulated..

Then you have two factors to adjust. Time and temperature. Start with 40°C and if nothing is happening then bump up some degrees and try again. But probably you don't want to go beyond 50°C.

You don't want to flatten to much either because then you will get radial problems (the grove getting egg shaped. So it is better to have some warp left than "over do it" and get flat and egg shaped. The record that is warped is already destroyed for ever. When vinyl has been prolonged it will not go back to its original shape. Never! Yes it will get flat but the damage is done and it is a longer circumstance on the grove. When vinyl is NOT like a rubber band and goes back to its original shape. It is more as a pizza dough. You will learn that lesson is you have a very warped one and when you have flatten it out.)

When you get a feel of what temperature to use then the procedure is rather straight forward.

(The pizza stone has two disadvantages one is that it will contain moisture that will not be able to escape between the stones and record label can get destroyed. That is eliminated by drying out them in the oven. Next is they're going to scratch the record surface. You need a paper between record and stone or have a simple papper inner sleeve.)

I usually use more time than temperature and may do it over the night when temperature will destroy much faster the record than time.