Effects of Drying Temperatures on the Occurrence of Sticker Stain in Japanese Cedar (Cryptomeria japonica D. Don)

Abstract

Sticker stain is a material defect that results from moisture migration during wood drying, often spoiling the appearance of the surface of wood products. The effect of drying temperatures on the occurrence of surface sticker stain was investigated using Japanese cedar (Cryptomeria japonica D. Don) and three types of stickers (air-dried Japanese cedar, aluminum, and stainless steel) under four drying temperatures (20°C, 50°C, 75°C, and 100°C). At lower drying temperatures, the air-dried wood sticker tended to suppress the occurrence of surface sticker stains, whereas higher temperature or metal stickers produced sticker stains with deep color. However, no definitive relation was shown between the initial moisture content and the extent of sticker stain with deep color regardless of drying temperatures. It was considered that the partial delay of drying happened around the contact area with stickers, especially in cases of metal stickers. It was also found that the use of metal stickers at higher drying temperatures induced depressions in Fourier transform infrared spectra related to the occurrence of hygrothermal conditions.

Influence of hydrothermal treatment on hemicellulose structure in Cryptomeria japonica

“…To supply quality-controlled timber with guaranteed moisture content, various kiln drying methods have been proposed. One of the common methods in wood industry is "high-temperature setting drying," consisting of the three processes; steaming at 95 °C, high-temperature treatment at 120 °C, and medium or low temperature treatment below 90 °C, which suppresses surface checks through thermal softening and relaxation of drying stress (Obataya et al 2006;Toba et al 2021;Jiang et al 2022).…”