The influence of storage/transportation conditions on drying stresses and the prong test

From the time lumber is removed from the kiln to the time the remanufacture r uses it, it can be exposed to many different humidities. With exposure to severe humidities, cupping in the final product can occur. This paper cons iders if humidity conditions during storage and transportation can signific antly influence drying stresses and prong test response. To determine the i nfluence of exposure to different humidities, dried lumber was slowly equil ibrated to 7.5% moisture content. It was than cut into blocks. The blocks w ere exposed to various humidity scenarios to simulate actual storage and tr ansportation conditions. Stress levels, moisture content and prong response were recorded. The analysis showed that stress level and prong response we re strongly influenced by exposure to different humidities. The analysis al so indicated that returning lumber to 7.5% equilibrium moisture content did not return the stress level or prong response to the original values. Thes e combined results confirm that the prong test cannot be used as an indicat or of how well the lumber has been dried or conditioned after it has been s tored and transported. This makes seller/buyer disagreements difficult to r esolve.