Effects of vacuum heat treatment and wax impregnation on the color of Pterocarpus macrocarpus Kurz.

Abstract

Pterocarpus macrocarpus Kurz. wood was vacuum heat treated (VHT)　at 120, 150, and 180 °C, under a pressure of 13.3 kPa. Half of the VHT specimens at 120 and 150 °C were subjected to wax impregnation　(WI) for 48 h at 90 °C under an atmospheric pressure. The effect of VHT and WI on wood color were investigated. The results showed that the VHT at 120 and 150 °C resulted in minor changes in lightness (L*), green-red chromatic coordinate (a*), blue-yellow chromatic coordinate (b*), total color change (ΔE*), and chroma (C*). However, the effect of VHT on L*, a*, b*, and C* at 180 °C became more obvious over the duration. After WI, the L*, a*, b*, and C* of the VHT wood at moderate temperatures varied noticeably, showing similar behavior with the VHT wood at 180 °C as L*, b*, and C* decreased and ΔE increased. However, a* increased after WI compared to that of VHT at 180 °C. The wood color of P. macrocarpus Kurz. after WI became reddish and blue, and the color deviation decreased. The wood color was closer to the dark mahogany, which facilitates its further application in rosewood furniture and woodwork art.