Scratchplates can easily bend if they get hot. Never work on one out in direct bright sunlight as it doesn't take much for it to warm up and start twisting. I ruined a whole sheet of black scratchplate material because I'd put it down outside on a Workmate for 20 minutes and it turned into a Daliesque work of art. Even a lighter-coloured mint-green pickguard had a slight warp in it after a few minutes in hot sun.