Effects of HTLH and Kerfing Pretreatement on the Drying Characteristics of Large Square Red Pine Timber

In this study, the effects of two different drying techniques on the properties and characteristics of large square Korean red pine timbers were examined. Wood specimens with a cross section area of 200 X 200 mm and length of 3600 mm were subjected to high temperature and low humidity (HTLH) pretreatment followed by air-drying or radio-frequency/vacuum (RF/V) drying, and the result specimens were compared. The effect of longitudinal kerfing on drying properties was also examined. The total time of RFA" drying after HTLH pretreatment was 245 h, which led to a decrease in the initial moisture content (MC) of 83% to a final MC of 5%. RF/V drying was faster than air drying, and the difference in final MC between the internal and external layers of RF/V-dried large square timber was approximately 2%. The slopes of moisture gradients along the thickness directions were very smooth. Our results also indicated that surface checks were effectively prevented by kerfing treatment: no surface checks were observed on kerfed and RF/V-dried timbers. Irrespective of kerfing, very few drying defects of internal checking and twisting were found on RF/V-dried timbers. Case hardening was less than 4% after drying.