COLOURING OF BEECH WOOD DURING THERMAL TREATMENT USING SATURATED WATER STEAM

In this paper, there are presented the results of colour change of beech wood in the process of thermal treatment - steaming using saturated water steam. In this process, the colour of beech wood changes from pale white-grey with a yellow tint through brown-pink to a dark red-brown colour, depending on the conditions of technological process. In this paper, there are presented the colours of beech wood achieved during the thermal treatment - steaming with saturated water steam at temperatures: t(I) = 112,5 +/- 2,5 degrees C for the duration tau = 5,5 h, t(II) = 127,5 +/- 2,5 degrees C for the duration tau = 6,5 h and t(III )= 137,5 +/- 2,5 degrees C for the duration tau = 7,5 h The colour of beech wood steamed by regime I. changes to a pale brown-pinkish yellow colour with CIE-L*a*b* colour range coordinates: L* = 68,4 +/- 2,8; a* = 10,1 +/- 2,3; b* = 20,6 +/- 1,3, regime II. changes to a brown-pink colour with colour coordinates: L* = 58,1 +/- 3,8; a* = 15,5 +/- 2,2; b* = 24,9 +/- 1,3 and regime III. changes to a dark red-brown colour with colour coordinates: L* = 53,2 +/- 2,4; a* = 17,9 +/- 2,0; b* = 26,1 +/- 1,5. With the increasing temperature of saturated water steam used in the thermal treatment, as well as prolonging the duration of steaming, beech wood loses its lightness (darkens) and an increase in the red colour coordinate a* and yellow colour coordinate b* in CIE-L*a*b* colour range induces this colour shade. This irreversible change of beech wood colour achieved by one of the regimes of beech wood steaming using saturated water steam broadens the possibilities of its use in construction, artistic, or design fields.