One-sided surface charring of beech wood

Čermák, Petr; Dejmal, Aleš; Paschová, Zuzana; Kymäläinen, Maija; Dömény, Jakub; Brabec, Martin; Hess, Dominik; Rautkari, Lauri

doi:10.1007/s10853-019-03589-3

Cited by 34 publications

(36 citation statements)

References 31 publications

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“…Wood modifications, such as thermal, chemical, or mechanical treatments, to improve the physico-mechanical properties are available [2,3]. In the area of surface modification by wood charring, applied temperature and time are key parameters to enhance surface performance [4,5]. Various scientific studies are currently dealing with the subject of one-sided surface charring to increase the natural durability of wooden facades with different positive results to the shelf-life duration or service time [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…However, the knowledge about the traditional charring process and its resulting material properties have not been scientifically assessed yet and available 2 of 11 information is rather limited. While some modern methods use a gas flame, an electric muffle furnace or a hot metal plate to achieve wood surface charring [5,6], the traditional Japanese manufacturing process, named "Yakisugi" or "Shou Sugi Ban", differs through the spontaneous combustion of sawn wood boards, which are used to produce the charred layer. Nowadays, a contact heating system by hot plate used for one-sided surface charring of wood allows greater control of the process conditions and provide uniform charred surface at temperature range of 200-400 • C [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Surface Modification of Spruce and Fir Sawn-Timber by Charring in the Traditional Japanese Method—Yakisugi

et al. 2021

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The traditional Japanese method of wood surface charring was studied. To perform the surface charring, three sawn Norway spruce and Silver fir wood boards of dimension 190 × 24 × 4000 mm3 were tied together to act as a chimney and charred in a short time (3–4 min) with open flame at a temperature above 500 °C. Temperature inside the chimney was recorded on the three different positions during the charring process. Surface temperature of spruce increased from 0 °C to 500 °C in approx. 120–300 s while fir increased in approx. 100–250 s. The thickness of the charred layer and the resulting cupping effect were investigated at the different heights of the chimney to evaluate its variability. Temperature achieved during the charring process was sufficient to get a significant charred layer of 2.5 and 4.5 mm on average for spruce and fir samples, respectively. The analyzed samples showed a significant cupping effect to the charred side with no difference between the annual ring orientation of sawn boards. Spruce exhibit a more significant cupping effect when compared to fir, i.e., 3.2–6 mm and 2.2–4.5 mm, respectively. Furthermore, the pH values of charred samples increased significantly, which could be an indication of improved resistance against wood-decay fungi. For better insight into the traditional charring method, further studies should be carried out to execute the charring process in a consistent quality and therefore fully exploit its potential.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Surface Modification of Spruce and Fir Sawn-Timber by Charring in the Traditional Japanese Method—Yakisugi

et al. 2021

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“…As a result of the surface micro cracks in the charred layers, water uptake is increased and causes additional surface damage due to the different internal stresses of the charred surface and untreated inner wood. The results indicate that the most important factors influencing the performance of one-sided surface charred beech wood are, not only the process parameters, i.e., temperature and time, but also the orientation of annual rings towards the heat flow, which may play a major role during a product's life [13,[44][45][46]. Density profile measurements can potentially be used as an efficient tool to verify the charring process intensity and further optimize the process according to specific requirements.…”

Section: Resultsmentioning

confidence: 99%

“…The thermal modification of wood at elevated temperatures (160-260 • C), as one of the most commonly used commercial methods, decreases the equilibrium moisture content (EMC) and improves its dimensional stability and biological durability [9]. An alternative to traditional thermal modification is to modify only the exposed surfaces, saving time and costs, and preserving the material properties of the interior of the wood [10][11][12][13]. Recent scientific work shows that wood can be one-sided surface charred using a hot plate under controlled conditions-i.e., temperature and time-leaving the structural properties of the wood relatively unchanged [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…An alternative to traditional thermal modification is to modify only the exposed surfaces, saving time and costs, and preserving the material properties of the interior of the wood [10][11][12][13]. Recent scientific work shows that wood can be one-sided surface charred using a hot plate under controlled conditions-i.e., temperature and time-leaving the structural properties of the wood relatively unchanged [11][12][13]. It is well known that wood undergoes a number of overlapping chemical reactions as a result of thermal degradation when high temperatures are applied.…”

Section: Introductionmentioning

confidence: 99%

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Effect of One-Sided Surface Charring of Beech Wood on Density Profile and Surface Wettability

et al. 2021

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One-sided surface charred European beech wood (Fagus sylvatica L.) was studied. Radial and tangential specimens of dimensions of 50 × 25 × 350 mm were one-sided surface charred at 200, 250, 300, 350, and 400 °C for various times using a contact heating system. Specimens of dimensions of 50 × 25 × 50 mm3 were prepared for treatment intensity analysis and its effect on surface wettability. Density profiles of the radial and tangential charred specimens were determined using X-ray densitography with a resolution of 0.05 mm. The wettability of the one-sided surface charred wood specimens was analyzed via contact angle, measured using the sessile drop method and determined over 10 to 150 s. The oven-dried specimens were partially submerged in water and water uptake was recorded after 2, 4, 6, 8, 10, 48, and 72 h according to EN-927-5. The surface density of the radial specimen groups charred at 200 °C for 6 min and 250 °C for 4 min decreased by about 4.5 to 8.2%. With increasingly severe charring, the surface density decreased by about 15.5 to 33.5%. A mild charring process produced a surface charred layer of approx. 2 mm, while higher temperatures and longer times affected the density up to 4–6 mm beneath the surface. Differences were found between the water uptake of the radial and tangential charred beech specimens. The most significant decrease of 56% in water uptake was recorded for the radial group prepared at 200 °C for 20 min after floating in water for 72 h. Water uptake in the radial groups modified at 250 °C for 4 and 6 min after 72 h decreased by 38% and 36%, respectively. The tangential groups did not show any statistically significant decrease. The average water uptake of the groups charred at 200 °C for 20 min, 350 °C for 2 min and 400 °C for 1 min was greater than that of the reference; the variability of the measured data was significantly greater due to the highly anisotropic character of the tangential specimens. Micro cracks were also visible on the surface. Concluding from the results of this study, one-sided surface charred beech wood exhibits increased potential in terms of wood–water related properties when a temperature range of 200–400 °C is applied.

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Effects of aluminum sulfate soaking pretreatment on dimensional stability and thermostability of heat-treated wood

et al. 2020

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Acidic aluminum sulfate hydrolysis solutions can be used to catalyze the thermal degradation of wood in a mild temperature environment, and thus reduce the temperature required for heat treatment process. To improve the dimensional and thermal stability of Chinese fir during heat treatment at 120 °C, 140 °C and 160 °C, this study investigated the effects of soaking pretreatment with 5%, 10% and 15% aluminum sulfate on the chemical and structural changes of the heat-treated Chinese fir. The results indicated that the samples treated at 15% aluminum sulfate concentration and 160 °C heat treatment achieved the best dimensional and thermal stability. Chemical analyses by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the catalysis of aluminum sulfate resulted in degradation of hemicelluloses during the heat treatment, and an increase in the soaking concentration and heat treatment temperature also affected the thermal degradation of celluloses. The scanning electron microscope (SEM) and mass changes test results proved that the hydrolyzed aluminum flocs mainly adhered to the inner wall of the wood tracheid as spherical precipitates, and when the soaking concentration reached 10% and 15%, a uniform soaking effect could be achieved. The thermogravimetric (TG) analysis revealed the soaking pretreatment effectively improved the thermal stability of the heat-treated wood by physically wrapping and promoting the formation of a carbon layer on the wood surface during heat treatment. Thus, aluminum sulfate soaking pretreatment exerted a great effect on the dimensional and thermal stability of wood, allowing heat treatment to be performed at a lower temperature.

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One-sided surface charring of beech wood

Cited by 34 publications

References 31 publications

Surface Modification of Spruce and Fir Sawn-Timber by Charring in the Traditional Japanese Method—Yakisugi

Surface Modification of Spruce and Fir Sawn-Timber by Charring in the Traditional Japanese Method—Yakisugi

Effect of One-Sided Surface Charring of Beech Wood on Density Profile and Surface Wettability

Effects of aluminum sulfate soaking pretreatment on dimensional stability and thermostability of heat-treated wood

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