The dry-bulb temperature inside the kiln commonly rises when conditioning lumber. It is important that the dry kiln operator remember that the actual dry and wet bulb dictate the conditions in the kiln. If it is difficult to obtain a high EMC, let the kiln cool down for several hours prior to conditioning. Then turn on the steam spray by raising only the wet bulb on the control. Observe the controller and see what EMC the kiln conditions achieve.
Conditioning is completed only when drying stresses are relieved.
When boards are being conditioned, the moisture content of the surface will be about three percentage points above the core of the lumber. Stress samples should be cut to determine if the lumber is conditioned and evaluated several hours later. Prongs should be one fourth the thickness of the lumber. If after several hours the prongs are standing straight up, the lumber is properly conditioned. If the prongs are pinched together, the lumber still contains stress.