Abstract: In a method of drying boards by radio-frequency heating a stack of boards is passed between live and earthed electrodes. The connections to the electrodes are periodically reversed so that each is alternately live and earthed; this increases the uniformity of heating in the stack. Preferably the boards are stacked in short spacer sticks to delay the escape of steam from intermediate boards in the stack and reduce surface checking. The escape of steam from the top and bottom boards of the stack to be dried can be delayed by using top and bottom covering boards treated with a liquid substantially unaffected by radio-frequency heating.