• Cristina Marinela Olarescu Transilvania University of Brasov, Romania
  • Mihaela Campean Transilvania University of Brasov, Romania
Keywords: color change, heat treatment, mass loss, wood


Heat treatment is renowned as the most environmentally friendly process of dimensional stabilization that can be applied to wood, in order to make it suitable for outdoor uses. It also darkens wood color and improves wood durability. The intensity of heat treatment can be appreciated by means of two parameters: the color change occured in wood due to the high temperature, and the mass loss, which is a measure of the degree of thermal degradation. In order to find a mathematical correlation between these two parameters, an experimental study was conducted with four European wood species, which were heat-treated at 180°C and 200ºC, for 1-3 hours, under atmosheric pressure.

The paper presents the results concerning the color changes and mass losses recorded for the heat-treated wood samples compared to untreated wood.  For all four species, the dependency between the color change and the mass loss was found to be best described by a logarithmic regression equation with R2 of 0.93 to 0.99 for the soft species (spruce, pine and lime), and R2 of 0.77 for beech. The results of this study envisage to simplify the assessment procedure of the heat treatment efficiency, by only measuring the color – a feature that is both convenient and cost-effective. 


Allegretti, O., Brunetti, M., Cuccui, I., Ferrari, S., Nocetti, M., & Terziev, N. (2012). Thermo-vacuum modification of spruce (Picea abies Karst.) and fir (Abies alba Mill.) wood. BioResources, 7(3), 3656–3669.

Alén, R., Kotilainen, R., & Zaman, A. (2002). Thermochemical behavior of Norway spruce (Picea abies) at 180 - 225°C. Wood Science and Technology, 36, 163-171.

Bal, B. C. (2014). Some physical and mechanical properties of thermally modified juvenile and mature black pine wood. European Journal of Wood and Wood Products, 72(1), 61-66.

Bekhta, P., & Niemz, P. (2003). Effect of high temperature on the change in color, dimensional stability and mechanical properties of spruce. Holzforschung, 57, 539-546.

Bobleter, O., & Binder, H. (1980). Dynamic hydrothermal degradation of wood. Holzforschung, 34, 48-51.

Borrega, M., & Kärenlampi, P.P. (2008). Mechanical behaviour of heat-treated spruce (Picea abies) wood at constant moisture content and ambient humidity. Holz als Roh-und Werkstoff, 66, 63–69.

Campean, M., Gurau, L., & Olarescu, A. (2011). Effect of heat treatment upon dimensional stability and static bending strength of sessile oak wood. PRO LIGNO, 7(2), 46-55.

Clauder, L., Maschmann-Fehrensen, A., & Seemann, F. (2009). Herstellung von thermisch modifiziertem Eichenholz [Production of thermally modified oak]. OakChain-Abschlusstagung. Eberswalde.

Esteves, M.B., & Pereira, H.M. (2009). Wood modification by heat treatment: A review. BioResources, 4(1), 370-404.

Gonzáles-Peña, M., & Hale, M. (2009). Colour in thermally modified wood of beech, Norway spruce and Scots pine. Part 2: Property predictions from colour changes. Holzforschung, 63, 394-401.

Kaymakci, A., & Akyildiz, M.H. (2011). Dimensional stability of heat treated Scots pine and Oriental beech. PRO LIGNO, 7(4), 32-38.

Kim, G., Yun, K., & Kim, J. (1998). Effect of heat treatment on the decay resistance and the bending properties of Radiata pine sapwood. Material und Organismen, 32(2), 101–108.

Kocaefe, D., Poncsak, S., & Boluk, Y. (2008). Effect of thermal treatment on the chemical composition and mechanical properties of birch and aspen. BioResources, 3(2), 517-537.

Korkut, S., Karayilmazlar, S., Hiziroglu, S., & Sanli, T. (2010). Some of the properties of heat-treated sessile oak (Quercus petraea). Forest Products Journal, 60(5), 473-480.

Mazela, B., Zakrzewsky, R., Grzeskowiak, W., Cofta, G., & Bartkowiak, M. (2003). Preliminary research on the biological resistance of thermally modified wood. The Proceedings of the First European Conference on Wood Modification.

McLaren, K. (1976). The development of the CIE (L*a*b*) uniform colour-space and colour-difference formula. Journal of the Society of Dyers and Colourists, 92, 338-341.

Oelhafen, M. (2005). Untersuchungen der Eignung der thermischen Behandlung als Methode zur Farbegalisierung von Holz mit fakultativem Farbkern [Investigations of the suitability of thermal treatment as a method to dye leveling of wood with optional color core]. Hochschule für Architektur, Bau und Holz HSB, Biel.

Todorovic, N., Popović, Z., Milić, G. and Popadić, R. (2012). Heat treated beechwood. BioResources, 7(1), 799-815.

Viitaniemi, P., Jämsä, S., & Viitanen, H. (1997). Method for improving biodegradation resistance and dimensional stability of cellulosic products. US Patent N° 005678324.

Wagenführ, R. (2008). Holzatlas. Fachbuchverlag Leipzig, Carl Hanser Verlag München-Wien.

Zivković, V., Prša, I., Turkulin, H., Sinković, T., & Jirouš-Rajković, V. (2008). Dimensional stability of heat treated wood floorings. Drvna Industrija, 59(2), 69-73.