Changes in spiral grain direction in ponderosa pine

Abstract

Standing dead trees that have lost their bark frequently exhibit checks in the wood running at variance from the lengthwise axes of the trees. In some trees, these checks spiral to the right; in others, to the left of the observer. They show the direction of the grain of the wood on the surfaces of the tree trunks. Variation in the degree of this spiral grain both in the exterior and interior parts of trees is of interest, since grain direction with reference to the axis of a piece of timber influences strength, warping during seasoning, and twisting of posts and poles. Reversals of grain direction within the trunks of trees indicate the presence of opposing forces that might influence the behavior of wood, particularly the twisting of round products.

Citation

Paul, B.H. 1956. Changes in spiral grain direction in ponderosa pine. Rep. FPL-2046. Madison, WI: U.S. Department of Agriculture, Forest Products Laboratory. 9 p.