A SIMPLE PROCESS OF WOOD CARBONIZATION AN D THE CHARACTERISTICS OF WOOD CARBONIZED AT LOWER HEAT TEMPERATURES

A new simple method to make carbonized wood was tested. To do this, a steel cylindrical can (130 mm diameter x 180 mm height) filled with sa nd was inserted into an electric furnace, and woods were carbonized in the sand. In this method, sand was used to produce anaerobic conditio ns around the wood, and an electric heater was used to control the tem perature of the sand. This process made wood carbonize easily. The dif ferences of the mechanical strengths and the degrees of hygroscopic sw elling were examined between the carbonized woods and the untreated on es. Sugi (Cryptomeria japonica D. Don), Western hemlock (Tsuga heterop hylla (Raf.) Sarg.), Sitka-spruce (Picea sitchensis (Bong.) Carr.), an d Mizunara (Quercus mongolica Turcz. var. grosseserrata Read. and Wils ). were carbonized by this simple method at lower heat temperatures (a bout 300 degrees centigrade). Carbonized woods, especially softwoods, showed less strengths under compressive loads compared with untreated ones. Carbonized woods, at the same time, showed decreasing rates of i ncreases in moisture contents and hygroscopic swellings from oven drie d to 90% relative humidity compared with untreated woods. When periodi c changes of dryness and moisture were repeated for 100 hours with a w eather meter, the volume of each carbonized wood had smaller changes t han did untreated woods.