Rupture of Pit Membranes in Sugi (Cryptomerica japanica D. Don) Logs by a Smoke Heating System with Increased Far-Infrared Radiation

Abstract

Summary A special furnace for smoke-heating logs, with increased far-infrared radiation (FIR), was produced to improve the wood quality. Green sugi (Cryptomeria japonica D.Don) logs were smoke-heated with the direct use of this system. In a short time, this process increased the temperature inside the logs up to 80–100 °C uniformly, without any damage to the wood. The great increase in steam pressure inside the log resulted in the rupture of pit membranes (PMs) with a high frequency, leading to a decrease in the moisture contents of the logs. It was found that when a temperature of 80 °C is attained inside the log, the rupture of PMs occurs. The rupture proceeds from the outer sapwood towards the pith, accompanied by the radiation heat transfer within the log. By the rupture of PMs, smoke-heated sugi wood showed a large improvement in permeability.