How best to eliminate LP warps

I think the premise behind flattening the LP by heat and pressure is the hope that the LP WILL return to its original flat shape, that the stretching represented by a warp, if it is indeed stretching, will be eliminated by a corresponding shrinkage. I must say I don't quite understand your argument that warps can never be "repaired".  Anyway, when you play a warp, the warp itself does represent a longer distance between points A and B on the adjacent flat surfaces on the LP, as you say, and because the turntable motor maintains a constant angular velocity in the plane of the platter, the velocity of the stylus in the angular direction will increase momentarily between the flat points A and B, as it has to climb and descend a hill.  That ought to cause a pitch change.  Possibly, because this distortion occurs amidst musical passages, which are complex both in pitch and timing, perhaps that is why we may not hear a problem.  The video that Mijostyn put up here on this forum, when we were discussing tonearm design clearly does show that if the LP is encoding a pure tone, e.g., 1000Hz in the case of the video about the ARXA turntable and its wonderfulness, you CAN hear the warp.

@baylinor 

If I insulted you I'm sorry but I was hoping you got my joke.  The icon/photo you have on the upper left corner of your posts is the cover of David Bowie's "Aladdin Sane."  I'm willing to bet that Bowie came up with the title as a play on words for the phrase "A lad insane." In any event, Aladdin Sane may be my favorite rock album. My intention was to raise a toast to your good taste.

That one went right over the top of my head lol. Was wondering what you were referring to. The lad made me think you were english.  Thanks for the explanation, it restores my view of humanity 🙂

"No it is actually not, a wrapped record is stretched but all is depending on how bad the warp is"

optimize-

yes, that's what I envision what's physically happening. I'm thinking a  simple flattening during playback thru a VPI type outer weight makes more sense to preserve the LP, rather than any heating and prseeing/flattening of the disc?

Perhaps once an LP is warped, any attempts at straightening are technically(maybe not audible) compromising integrity of the groove? 

Because I'm a period press fan, I've got more than a few great albums, but they're real zingers-like a mogul ski run for the cartridge.

@lewm 

I think the premise behind flattening the LP by heat and pressure is the hope that the LP WILL return to its original flat shape, that the stretching represented by a warp, if it is indeed stretching, will be eliminated by a corresponding shrinkage.

Yes we might think and hope that shrinkage will happen.

Why should it shrink when we pressure it between two surfaces? It is not rubber.🤔

If you increase one, two or all three of the parameters temperature, pressure or time. It will only result in a bigger and thinner disc an it will never shrink back to its previous shape. Why should it? 🤔

That is exactly what is happening. The disc will be flatt (that is not a problem to achieve) but it's diameter has also increased by a very little bit when we apply as little force and heat we can get away with to just make I flat but the diameter will not magical decrease.

As I said it is small and something probably not something we can easily detect with small warps but the mechanics is the same. But if you have severe warped records you will also be able to flatten them out that part is not a problem to fix.

But you have now instead a severe wobbly grove that is not perfectly circular shaped. Yes you can only convert from one problem (warp) into another (egg shaped). When there is no shrinkage going on..🥰

I have first hand experience with a very warped record that I flatten out carefully over several iterations when I applied pressure and temperature during the whole night for each night and iteration when I did not get it as flat as I expected the first iteration. At the end I got it acceptable flat! (The iterations and time indicated that I didn't use to much heat so that it should destroy the record.) Yes, my happiness over that i had got the record flatter were shortlived when I saw the canteliver and cartridge work like crazy side to side! Never seen something like that in any of my 700 records and I concidered as still unplayable it looked as the needle should be thrown out of the grove, very disturbing. (Remember it were a badly warped record. So less warped will most likely give a less egg deformation). All the efforts was in vain. 🙁

Do you have any experience with record shrinkage? (Smaller warps will give smaller side to side movement but can be still OK and in tolerance, but it is impossible to know if it is little bit worse or not then it were before the warp event.)