if you only are flattening a couple of records; it is easy to do this yourself. all you need is a couple of clean plates of glass, an oven, and a way to clean the record. you can purchase the glass easily lots of places.
you clean the record first. then pre-heat the oven to about 180-190 degrees. place the record carefully between the clean sheets of glass. turn off the oven. then place the record 'sandwitch' carefully into the oven and allow it cool slowly.......be patient....wait until it is ambient temperature.
you might need some weight on top of the glass if it is a big warp but not much. this won't hurt an Lp.
i would recommend doing a test with a 'throw-away' Lp first to make sure that you don't make a mistake...the biggest caution is too much heat.
it's been a long time since i used this method. i think a standard residential window pane using tempered glass would be about right. too heavy and you could have the glass make an imprint on the grooves at the high spots. you are better off doing it twice than getting glass that is too thick.
a 12" x 12" window pane has sufficient weight to work.
as far as shattering the glass......make sure the glass is not cold to begin with......run it over increasingly warm water and then thoroughly dry it.
Just found an LP that sounds great(David Bowie-David Live mastered at Sterling by Robert Ludwig)but unfortunately is rippled with warps making the dynaflex nearly unplayable even with the VPI peripheral ring and center clamps. I decided I can't subject my stylus to this violent roller coaster ride and so am trying a variation on the Mikelavigne technique outlined above. I wasn't sure about the glass so I covered two pizza stones with aluminum foil(smoothly). I have preheated these to 180 degrees in the oven and will sandwich the LP until cool. Hopefully the weight of the stones and mild heat will solve the warping and the aluminum won't damage the vinyl. I have no idea how this will turn out but this was a lost cause anyway. I will post my results. Meanwhile, any comments? Will I need to reclean the LP now? Is warm aluminum toxic to vinyl somehow?
Well, I don't know about glass but the pizza stone trick definitely does not work at all. They probably store too much heat. After reaching room temp, the record was more notably warped than ever. I'm not really sure if I'll try the glass or just throw this one away. A cheap fix would be nice though. I think $1500 is too much for a disc flattener given how rarely I actually mistakenly buy a warped LP.
Grimace, Did you preheat the marble in the oven first or just stick the room temp sandwich in a preheated oven which had been turned off. I think my mistake may have been pre-heating my stones first. Anyway, sounds like marble works better than pizza stones.
I'd first line the inner sections of the marble with self sticking cork liner(found in a Home Depot type store,very cheaply).This will allow some flexure as grooves make contact,and should aid against groove "squishing"(from heat)-:)
I put the sandwich in cold, but left the heat on for 30-seconds or a minute or so, then turned it off. Those stones take a really long time to truly cool down. About three hours to room temp. Not hot, just warmer than ambient temp.
just be careful not to move the vinyl around between the stones, and start with something you can live without in case something bad happens.