I purchase a lot of new vinyl from Amazon. I know it isn't their fault but the pressing industry puts out a LOT of warped product lately. My theory is they are in too big of a hurry and removing too quickly, but really have no idea why it is so bad.
I had borrowed a friend's Vinyl Flat and decided to get my own. My model has a sunbeam heating pad built into their pouch with L/M/H setting. I use the L setting for 3.5 hours and then turn off and leave alone until the next day. It typically does the job whether it is a standard or heavy weight record. I don't see the problem as often with 180g records.
My friend's is an older model with a different heating source with only 2 settings. I had to use high for 3-6 hours. I first used my new one on H for 3 hours and well let's just say I was glad it was only a $15 dollar record. It made me laugh how it completely flattened out the grooves into a smear....I was like damn!!!
It initially seems like a lot to spend $200 but once you get over that it is very nice to be able to fix them and not worry about your cartridge or see that roller coaster effect.
I have not had any luck flattening older records. I honestly don't have that many old records that are warped but when I do occasionally get one I haven't been able to correct.
I highly recommend one! Good luck
