Sometimes it takes longer finishing your painting than you thought and you have to stop painting to go to an appointment. When you’re painting on wet paper (you wet both sides of the paper before you started painting), you can flip your board upside down on a surface that’s sealed so it will stay moist. Then the next day you can continue painting while the paper is still moist and flat on the board. I put some weights on it to keep the board tight to my table.