Radio frequency detection of compression wood in green loblolly pine

Compression wood is formed on the lower side of leaning softwood trees stem. High density and high microfibril angle lead to a very high rate of longitudinal shrinkage compared to that of normal wood. This shrinkage leads to a high degree of warp and resultant value loss in lumber during drying. Detection of compression wood in green lumber would allow segregation of the lumber for special handling or product designation and reduce value loss from warpage during drying. A dielectric method was used to detect compression wood in green loblolly pine lumber. Significant increase in the phase shift of an applied radio frequency signal was detected due to the special cellular structure of compression wood. A threshold value was determined which allowed identification of compression wood in lumber. This method resulted in very high success rate in separating compression from normal wood.