Sorption-related characteristics of surface charred spruce wood

Research output: Contribution to journalArticleScientificpeer-review


Research units

  • Mikkeli University of Applied Sciences
  • Mendel University in Brno


Surface charring of wood is a one-sided thermal modification process that can be used to create a hydrophobic, durable surface to exterior claddings. Spruce (Picea abies L.) wood samples were charred with a hot plate and several time-temperature combinations while using simultaneous surface compression. Temperature profile, water sorption, cupping after water exposure and density profile were measured. Furthermore, changes in the microstructure and surface functional groups were investigated by scanning electron microscopy and photoacoustic FT-IR spectroscopy. Results show that surface charring notably improves the hydrophobicity measured by contact angle, water floating and dynamic vapour sorption. Increased holding time during charring reduced the sorption but at the same time increased the dimensional instability measured by cupping. The density profile showed a shifting density peak with more severe modification regimes, indicating a more porous surface. The PAS-FTIR showed increased aromaticity of the surface that was also present in the pyrolysis zone beneath the surface in samples modified with longer holding time. Higher modification temperature affected the sorption as well as cupping positively but it is possible similar results can be obtained with lower temperature and longer holding time.


Original languageEnglish
Article number2083
Issue number11
Publication statusPublished - 24 Oct 2018
MoE publication typeA1 Journal article-refereed

    Research areas

  • Char, Surface modification, Thermal modification, Wood, Wood char

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