Development of moisture content distribution in sapwood and heartwood during initial stages of drying

45 mm boards of spruce, with high moisture content and parts of sapwood and heartwood, were dried at a temperature of 60°C and at a relative humidity of 77% (dT=5K; Ugl = 12%). The distribution of the moisture content about the cross section was estimated before and after different times of drying. Over a long drying time in the sapwood the humidity was higher than in the heartwood and only at the end of drying sapwood and heartwood reached the same humidity. Also from electrical measurements of the moisture content in the two zones their different behaviour in the drying process can be seen. If a drying process should be carefull, the position of the electrtode for the measuring of the moisture content as the controll member of the drying process, is very important. In addition to the observance of the distribution of sapwood and heartwood also the character of the annual rings is to be taken into account.