Green Kerfing Treatment for Improving Softwood Lumber Drying: A Review

Abstract

Kerfing is a lumber-drying improvement technique that consists of cuts along both sides of boards, transversal to the longitudinal axis. The rationale behind this procedure is that, by cutting the fibers, the moisture loss through the end-grain is increased. The aim of this paper is to evaluate the effects of kerfing on drying time, warp occurrence, and bending properties, based on different experiments conducted during the last seven years. In most cases, kerfing reduced the drying time by half of that of the control samples. Results were inconclusive regarding reduction of warp. Regarding the bending strength of treated pieces, kerfing caused a minimum loss of moment of inertia in the piece, resulting in a slightly lower bending strength and higher stiffness.

Keywords:

• Bending strength
• Drying
• Kerfing
• Warp

ACKNOWLEDGMENTS

The authors would like to acknowledge the contribution of Rajala Timber Co. (Deer River, Minnesota), which donated the material for this project. We wish to convey special thanks to Robert Seavey, Instructor and Research Associate at the University of Minnesota, for directing the tests. We would also like to thank Cory Stewart and Travis Smith, students at the University of Minnesota, who helped during the bending tests.

Notes

*Angle relative to the length of the specimen.

**DH = Dehumidification kiln.

***All specimens were end-coated.

*Statistical tests showed no significant differences between kerfed and controls.

N/A = Bow was not measured in RP4.