engleski

Research on colour variation of steamed cherrywood (Prunus avium L.)

Hydrothermal treatment of wood, especially steaming, is often used to achieve more intensive and homogenous colour of wood or to vary its hue. On cherrywood (Prunus avium L.) influence of steaming and drying on colouring of wood tissue was researched. Green, randomly selected cherrywood boards, 43 mm thick, were conventionally steamed in period of 60 to 72 hours, between 45 to 70°C. Low temperature kiln drying in conventional dryer followed afterwards, by successive rising of temperature from 30°C to 55°C, till 8% end wood moisture content (MCend) was reached. Wood colour was assessed visually and with standard 3-stimulus colorimeter, using CIEL*a*b* system, and compared to natural colour of cherrywood. Wide heterogeneity of hues was found out on specimens at the end of hydrothermal treatment, where only minorities of them reached target level. A huge amount of steamed wooden elements signifi cantly deviated (Δ E*=7.16), especially in lightness (L*) and in hue (hab) of wood colour, in comparison to the predefined reference. Desired, referent colour of steamed cherrywood has the lowest lightness (L*=59.6) and hue (hab=50), and the highest chromaticity (C*=25). Declining linear trend of lightness and hue from sapwood over heartwood and steamed elements to referent specimens was confirmed. There is clear indication of usefulness of colorimetry to asses and control steaming process of wood. Th ere are additional data for fi rst 18 hours of steaming where samples were taken for light microscopy analysis of parenchyma cells which confi rmed the decrease of cellular deposits during steaming treatment in sapwood, with complete elimination at the end of the procedure. In the heartwood, additional resin deposits were found out, whereas parenchyma globular deposits were not present in any wood specimen.

cherrywood (Prunus avium L.); hydrothermal treatment; wood colour; colorimetry; CIEL*a*b* system

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