Barry, one way is to use Acetone on the bottom side of the box call paddle, just rub some in the direction of the paddle length ways. It will remove any older chalk and slightly raise the grain for new chalk application. If you don't have any acetone, (walmart sells it), you may try rubbing alcohol, make sure there is no oil in in. After you clean it you could lightly sand it with 220, then chalk it, hope this helps, Jack