If this occurs, it is because the wood has absorbed moisture: the wood fibres have expanded on one side and shrunk on the other, causing this deformation. The panel must then be placed flat on trestles, in the opposite direction to the curve. Air must be able to circulate well around the panel. Above all, do not place a heavy load on the panel, or stand it up vertically. The room must be well ventilated, and at an ideal temperature of about 20°C. In winter, and to speed up the process, we can put an electric heater under the panel (set to medium power).
After a few days, the panel should regain its original flatness.
