Journal of Wood Science

, Volume 64, Issue 4, pp 406–416 | Cite as

Impact of thermal modification on color and chemical changes of spruce and oak wood

  • Adam Sikora
  • František Kačík
  • Milan GaffEmail author
  • Veronika Vondrová
  • Tatiana Bubeníková
  • Ivan Kubovský
Original Article


Thermal modification of wood is an environment-friendly alternative method for improving several properties of wood without the use of chemicals. This paper deals with the examination of color and chemical changes in spruce (Picea abies L.) and oak wood (Quercus robur F.) that occur due to thermal treatment. The thermal modification was performed at 160, 180, and 210 °C according to thermowood process. The color changes were measured by the spectrophotometer and described in the L*a*b* color system. Chemical changes were examined by wet chemistry methods, infrared spectroscopy and liquid chromatography. During the experiment, oak samples showed smaller color changes than spruce samples at all temperature values. During thermal modification, the content of cellulose, lignin, and extractives increases; however, the hemicellulose content drops by 58.85% (oak) and by 37.40% (spruce). In addition to deacetylation, new carbonyl and carboxyl groups are formed as a result of oxidation. Bonds in lignin (mainly β-O-4) and methoxyl groups are cleaved, and lignin is condensed at higher temperatures.


Thermal modification Spruce Oak Color changes Chemical changes 



The authors are grateful for the support of “Advanced research supporting the forestry and wood-processing sector´s adaptation to global change and the 4th industrial revolution”, no. CZ.02.1.01/0.0/0.0/16_019/0000803 financed by OP RDE and by the of the University-wide Internal Grant Agency (CIGA) of the Faculty of Forestry and Wood Sciences, project no. 2016-4309 (70%) and by the Slovak Research and Development Agency under the contract no. APVV-16-0326 (30%).


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Copyright information

© The Japan Wood Research Society 2018

Authors and Affiliations

  • Adam Sikora
    • 1
  • František Kačík
    • 1
    • 2
  • Milan Gaff
    • 1
    Email author
  • Veronika Vondrová
    • 1
  • Tatiana Bubeníková
    • 2
  • Ivan Kubovský
    • 3
  1. 1.Department of Wood ProcessingCzech University of Life Sciences in PraguePrague 6, SuchdolCzech Republic
  2. 2.Department of Chemistry and Chemical TechnologiesTechnical University in ZvolenZvolenSlovakia
  3. 3.Department of Physics, Electrical Engineering and Applied MechanicsTechnical University in ZvolenZvolenSlovakia

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