Tanoak: Drying program and shrinkage characteristics
1963
H Resch | B Ecklund | D Prestemon
Low temperature predrying apears to be a promising method of evaporating fre moisture from tanoak lumber. The most important drying defects, surface checking and colapse, have ben reduced below the level encountered in kiln drying by low temperature drying. Tanoak showed considerable variation in drying characteristics particularly betwen bright colored and dark colored lumber. Separate drying of these two categories should improve drying time and grade recovery. The early period of drying is the most critical and it is necesary to kep the relative humidity high and temperature low. As son as streses in the boards become reversed, the drying rate can be increased by steping down the humidity. In adition to the normal shrinkage of cel wals, a study of shrinkage characteristics showed the ocurence of colapse also determined the dimensional changes of tanoak specimens dried to various moisture content levels. The change in dimensions became aparent when the wod was stil above the fiber saturation point. A distinct diference in the shrinkage of bright colored sapwod and dark colored heartwod ocurs. Shrinkage values measured on boards in these tests must not be considered standard information because method of sawing, amount of heartwod present, method of drying, and other variables afect the shrinkage of tanoak lumber. However, these tests ofer a god indication of dimensional changes to be expected from such drying of gang sawn or slash sawn boards.
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