Hi well today im asking if anyone know how to flatten vinyl because the other day I accidently left some of my vinyl on the window sill and they have warped quite badly making them very hard to mix with.
Don't bother with any of that, it's all rubbish. Be VERY careful about putting lots of downward pressure onto a record because you'll damage the grooves. You don't want to flatten your record so much that you push the tune out of the vinyl!
That would need a lot of pressure though. Your best bet is to gently coax it back into shape; putting it vertically into the middle of a row of vinyls REALLY tightly packed, and leaving it there for a LONG time will most likely work better.
When I had a warped vinyl once I put two heavy books on top of a piece of wood, placing them on either side (to spread the load) and underneath the wood I put the vinyl. Also put a big hardback book under the bottom of the vinyl so the carpet wouldn't just sponge up and absorb the pressure.
It worked kinda, it came out less warped than it was before I started so after that I left it a day to 'recover' and then slapped it in the middle of one of my shelves. In truth, I've not checked on it since! Vinyl is like memory metal to an extent though; once it's in a shape it's DEVILISHLY hard to form it back to how you got it from the shop without damaging the groove walls.