HEARTVVOOD OF CRVTOMERIA JAPONICA 853 



somewhat grayish red after a short time and then progressively to deep 

 grayish brown as the outer part got shghtly dried, e. g., after about 

 two or three hours. The deepening of the tint gradually advanced 

 until it culminated in about eight hours, giving a dark brown color 

 which was kept for about two days. The color began then to bleach 

 out and changed to dull brown three weeks later. This tint lasted com- 

 paratively long, say, during two or three months. After that time it 

 faded slowly to a final light grayish brown when the board was almost 

 airdried five months later. Even this- final tint is subject to the general 

 very slow change of wood color on exposure to air and light. 



Notwithstanding the time necessary for arriving at each stage of the 

 conversion or completing the whole process, together with the density 

 of the colors, differing naturally with the cases, the deepening was 

 confined to the outer parts of the wood. On thinner test pieces pre- 

 pared from the same material and subjected to rapid seasoning, putting 

 in air or water-bath, the change of tint was limited to the superficial 

 parts and not so deepened as the control left in the room under nat- 

 ural conditions. As the shavings from the inner parts of these test 

 pieces were yet able to follow a deepening process in the same in- 

 tensity, when they were kept again under moist conditions, the exist- 

 ence of ample moisture is clearly one of the conditions necessary to 

 the deepening; but light had no influence upon it. While hydrogen 

 and oxygen accelerated the process, test pieces kept on exposure to 

 carbon dioxide were not only unstained but also rather bleached out. 

 But, on the other hand, the control tests with normal "red wood" kept 

 in the moist condition showed the same kind of the deepening to some 

 extent. Even timbers of "red tree" left in shady woods show the 

 darkening at least at the ends. Lumber from the same source becomes 

 dull colored when it is piled for a long time under moist conditions, 

 as is sometimes the case in sawmills. Furthermore we are confronted 

 by the more familiar examples that the "red wood" used in the parts 

 of our buildings exposed to moisture show a somewhat similar dark- 

 ening. Thus, at first sight, it appears that moisture is the primary 

 rather than the secondary cause of this phenomenon. Yet, the darken- 

 ing attained by "red wood" in these cases occurs far more slowly and 

 is not so dark in comparison with that of "black wood" in correspond- 

 ing cases. So the moisture content, by which "black wood" deviates 

 from "red wood," can not be considered as the direct cause, although 

 it and air are the conditions necessary for darkening. 



