Gérard Janin

AESTHETICS APPRECIATION OF WOOD COLOUR AND PATTERNS BY COLORIMETRY: PART 1. COLORIMETRY THEORY FOR THE CIELAB SYSTEM

The colorimetry theory for the CIELab system today allows us to compute the chromatic coordinates of the raw timber colour along the wood - chain industry. The wood industry is nd strongly behind in such areas. Progress in the wood appearance description by means of colour and pattern characteristics would be suitable to classify the wood. It would also help to match pieces of wood in furniture and inside the houses, to study the wood colour change in wood ageing by photodecoloration or by drying operations, and to improve wood colour variability. Key Words: wood colour; colorimetry theory.

Características tecnológicas das madeiras de Eucalyptus grandis W.Hill ex Maiden e Eucalyptus cloeziana F. Muell visando ao seu aproveitamento na indústria moveleira.

This work was carried out at Universidade de Brasilia at the Wood Products of Forestry Laboratory (IBAMA, Brasilia, DF, Brazil). Two species of eucalypt wood ( Eucalyptus grandis W.Hill ex Maiden and Eucalyptus cloeziana ) were studied to supply the furniture making industry. The wood of Eucalyptus grandis W.Hill ex Maiden shows physical properties (density and retractibility) and mechanical properties (static bending and hardness) very suitable for the industry of wood furniture. Such characteristics are complemented by its excellent behaviour in machining and also good finishing with varnishes. The colour and patterns the wood bring to the consumers a good feeling as well as for the furnitures built with such a species. The wood of Eucalyptus cloeziana, in spite of its mechanical and physical properties higher than those of Eucalyptus grandis W.Hill ex Maiden, presents good characteristics for the manufacture of furniture. Its grey-olive colouring is consistent with a good choice and taste for the consumers. However, some precaution must be observed during the machining of the wood. This wood’s hardness makes it suitable for parquetry.

APRECIACIÓN CUANTITATIVA DEL COLOR DE LA MADERA POR COLORIMETRÍA: PARTE 2: MEDICIONES DE LOS CAMBIOS DE COLOR EN PINO RADIATA (PINUS RADIATA) SECADO BAJO UN PROGRAMA CONVENCIONAL ACELERADO

espanolEn la primera parte de este trabajo se presentaron las bases teoricas en las que se sustenta la medicion cuantitativa y objetiva del color de un material. En base al sistema CIELab, se cuantifican los cambios de color de la madera de pino radiata Pinus radiata observados durante el secado industrial bajo un programa convencional acelerado. Los resultados confirman que las mediciones cuantitativas del color en la superficie de la madera permiten detectar la presencia de los cambios de color productos del secado por debajo de la superficie hasta una profundidad de 3 mm. Tales cambios de color son influenciados por la heterogeneidad de los anillos de crecimiento: relacion madera inicial/madera final y el ancho de anillos. Ademas permiten adaptar el programa de secado de acuerdo al nivel de intensidad de la coloracion permitida. EnglishOn the first part of this work the colorimetry theory for the CIELAB system was presented. In this paper the drying discoloration of radiata pine Pinus radiata at accelerated temperature was measured quantitatively and objectively. The results showed that the kiln brown drying would be detected until 3 mm below the surface by colorimetry and that this parameters values were influenced by the heterogeneity of the annual ring: earlywood/latewood relation and annual ring width. Also this measurements of the wood colour changes can allow to adjust the drying schedule in according to the coloration intensity allowed.