Heat treatments and drying lumber of Japanese raisin tree

Abstract

The purpose of this study was ascertaining the influence of heat treatments in the drying rate and wood quality of Japanese raisin tree (Hovenia dulcis Thunb.). In order to do so, four trees with 25 years and average diameter at breast height of 39.5 cm and an average commercial height of 10 m, were harvested and transformed into samples of 40 x 130 x 500 mm (thickness x width x length), and classified as to the radial and tangential orientation of the material. The treatments consisted of heating in water by 12 and 24 h at 85 ºC, and freezing by 12 and 24 h at - 18 ºC. Then, the lumber was subjected to drying at 75 °C in a forced convection greenhouse until reach 12% of final moisture content. The freezing and heating treatments have proven to be influential on the drying rate, since the first accelerated the drying process, whereas the other one decreased. The freezing treatment by 24 h with samples oriented in the tangential direction showed higher drying rate compared with the others. The treatments presented to be not significant for the reduction of the contractions in the samples related to width, thickness and length. However, the volumetric contraction was significantly higher in samples heated in water. The Hovenia dulcis wood did not show top or surface cracks in any of the treatments used in this study.