Hi guys! Happy New year!
I pulled out a set of Madagascar Rosewood back and sides from my stickered storage (about 6 years) and discovered that the back halves have cupped or warped (one side more than the other. See Pics). What do you do to try to flatten backs and tops?
I typically add plenty of water to the wood and then let it dry for a couple of days or a week sandwiched between two strong flat wooden cauls with a lot of clamps. I use a cloth of some kind that can let the moisture pass through on both sides between the cauls and the piece of wood, so I won't glue the wood to the cauls. Either with glue residue or oil from the wood.
It will at least flatten the wood long enough to glue the halves together, sand it to thickness and glue the braces.