Influence of Material Characteristics on Warp In Norway Spruce Studs

Marie Johansson, Robert Kliger


The aim of this study was to find parameters that cause warp. The study comprised 190 studs (45 X 95 X 2500 mm) of Norway spruce (Picea abies) from Sweden. Warp was measured five times in different moisture conditions. A number of parameters were registered on the studs, for example, average distance from the pith, grain angle, amount of juvenile wood, ring width, compression wood distribution on the surfaces, knots, cracks, wane, density, and modulus of elasticity. Grain angle and annual ring curvature were found to explain 73% of the variation in twist. Bow and crook were not possible to explain with statistical models. However, the distribution of compression wood on the surfaces of the studs could most often reveal the direction of bow and crook.


Twist;bow;crook;compression wood;grain angle

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