Solid wood surface modification by charring and its impact on reaction to fire performance
2021
Buksans, E., Forest and Wood Products Research and Development Inst., Jelgava (Latvia) | Laiveniece, L., Forest and Wood Products Research and Development Inst., Jelgava (Latvia) | Lubinskis, V., Pavasars, Ltd., Rauna Parish, Smiltene Municipality (Latvia)
Wood surface modification by charring is known for centuries, as Japanese craftsmen used this wood protection method for wood usage in outdoor exposure. This technology is well known as Shou sugi ban or Yakisugi and this treatment creates a thick char layer on the wood element surface, which later protects wood from biological attack for decades. Nowadays, it has become also a popular wood treatment method in the EU countries, mainly for decorative purposes. Wood surface modification by charring followed by brushing creates decorative looking wood surface with nice dark texture of latewood and light earlywood. The aim of this research was to develop a technology for decorative wood surface modification by the charring method and evaluate its impact on reaction to fire performance. Reaction to fire performance of modified wood prototypes was tested by the cone calorimeter method as a small-scale test and a single burning item (SBI) was used for large scale testing, which allows to determine the reaction to fire class according to the EU official classification system according to EN 13501-1:2018. It was found that wood surface modification improves reaction to fire performance of modified wood, when the char layer remains as facing, but decreased fire performance was observed, when the char layer removed by brushing. Additional fire retardant treatment application on modified wood surface was investigated to evaluate potential of reaction to fire class improvement. However, it is more difficult to improve reaction to fire performance of modified wood with charred surface compared to untreated wood.
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