Colour modification and homogenisation of larch wood by steaming
Larch (Larix decidua L.) wood samples were steamed applying broad range of steaming time (0-20 days) at 90°C and 110°C steaming temperatures. The colour change was monitored by objective colour measurement using the CIE Lab colour system. The initial colour of earlywood and latewood within sapwood and heartwood has highly different values for larch wood. Wide range of colours was created by steaming between the initial colour and brown colour depending on the steaming time and temperature. The steaming produced excellent colour homogenisation and resulted in an increase of saturation. The redness showed the greatest homogenisation effect. The redness value difference among the tissues was seven times smaller after 9 days of steaming at 110°C than the initial redness difference. The yellowness values increased and moved toward each other during steaming. The results showed that the best visualisation effect of homogenisation can be presented on the a*-b* plane. The colour saturation of the examined tissues increased considerably and showed homogenisation effect as well. Because of the colour homogenization, it was difficult to differentiate sapwood and heartwood at the end of the steaming process at 110°C. The effective steaming time for colour homogenisation was 5 and 2 days at 90°C and 110°C, respectively.