Original paper(Vol.46 No.4 pp.408)

Occurrence of irregular staining zone in partial coloring of beechwood utilizing selective penetration

Yata Shigeki; Ishikawa Tadaharu

Abstract:For the development of partial coloring technique of Japanese beech (Fagus crenata), five logs of air dried wood were penetrated with a dye solution by the capillary rise method and the vacuum impregnation method. The penetration rate into wood by capillary tension of liquid showed a wide variation among the five logs. In the permeable sample (No. 5 log), the dye solution was selectively penetrated into earlywood, so that color contrast between earlywood and latewood was emphasized. A thin impenetrable zone existed in the close vicinity of the surface of sound wood as No. 5 log, in which the vessels had been entirely blocked up by tyloses. Tylose development, after felling and cutting of tree trunk in summer, appears to be the natural defensive mechanism of wood against drying out. For the prevention of the tylose development, it may be necessary to immerse wood in a hot bath at a temperature above 50 deg., immediately after felling and cutting the tree in winter.
In the poor permeable sample, the bark seam and the encased knot were found in trunk. Penetration of dye solution in the growth related defects and their neighboring tissue was frequently stopped by tylose. Typical tyloses were detected in the growth related defects. It is considered that the blockage of vessels arise in the wood of living tree. Therefore, it is unsuitable to use the wood including these defects for partial coloring.
In the case of impregnation by the vacuum evacuation and subsequent atmospheric pressure, the dye solution penetrated easily into the less permeable tissues, where penetration by capillary tension was difficult. However, in No. 3 log which was the most impermeable wood, the unstainable spot remained.

Key Words:irregular staining, partial coloring, selective penetration