Changes in the equilibrium moisture content of a piece of wood often result in the surfaces being under tension while the interiors are under compression. In order to prevent warping, cracking and checking, the relative humidity should be kept as constant as possible, between 45% and 65%. Excessive moisture (around 70%) should be avoided lest fungi develop. Insect attack by woodboring beetles may be controlled by organochlorine insecticides but termites usually require a professional exterminator. The flaking of paint from polychromed wood sculpture has in some instances been controlled by impregnation by immersion in molten wax.