Fixing a warp
I'm building set of cabinets for my mudroom out of birch ply for the boxes, with doors that are simple stile & rail (aspen) mortised for a 1/2" birch panel. After I finished constructing the doors, I noticed that a few of them were slightly warped. I clamped one end of one of the doors to my workbench, put a piece of 1x under the low corner, and clamped the other corner down to persuade the door back to flat.
After 24 hours in the clamps, there was no difference. So I did it again but this time I spritzed the back of the door with water from a spray bottle. Twenty-four hours later, I removed the clamps and the door was perfectly flat, so I repeated it with the other 3.
Then I stained them & did 3 poly coats, and now they're slightly warped again. Is it possible to permanently remove the warp? I'm afraid to spray them again now that they're stained, and since they're pretty well sealed at this point I don't think the water do anything anyway. I suspect they warped in the first place because aspen's pretty soft; I should have used a harder wood.