This study examined the changes in the properties of beech wood (Fagus sylvatica L.) after intense drying. Beech wood with false red heartwood was selected as the test specimen. The test samples had dimensions of 50 mm thickness, 180 mm width, and 350 mm length. The specimens were divided into two groups, false red heartwood and sapwood. These specimens were selected with different angles of the growth rings (radial and tangential). The results showed that samples with red heartwood, in comparison to samples with sapwood content, had a remarkable effect in covering. Observation of specimens with false red heartwood and sapwood before and after drying process revealed significant differences in color changes and measured values during the covering-slicing test, but not between samples with different growth ring angles.

ABSTRACT

Structure of wood can affect intensity of color change in remarkable ways. This article was focused on the analysis of the color changes red false heartwood and mature wood by different methods such as ∆E* (Total color difference), h* (Hue angle), C* ab (Color saturation) and S ab (Saturation). The aim of this study was to evaluate the color properties of red false heartwood and mature wood by using different chromacity coordinates. Our observations suggested that the density in the absolute dry state was equal between the red false heartwood and mature wood. The biggest difference was in the area of the free water domain, thus from an initial MC value to the fiber saturation point (FSP). The shorter drying time of the red false heartwood samples was caused by their lower initial MC. Due to the different MC, the temperature created a different color intensity of the compared samples. Mature wood samples achieved more saturated color in the drying process than did the samples of red false heartwood.

No abstract

Drying time reduction has always been a major concern in the drying process and is achievable by increasing the temperature of the surrounding air. To optimize the quality of the resulting material, drying conditions must be enhanced to reach a balanced correlation between the drying time and quality of the dried timber. This paper analyses the hightemperature drying of wood and the optimization of this process, as well as the effect that drying temperature and thickness of beech timber specimens has on the drying process. The high-temperature drying of beech wood was carried out by means of hot air in a laboratory drier for maximum 33 hours at maximum temperatures of 130 and 150 °C. The initial moisture content of samples was approximately 70%. The resulting drying times were short in comparison to conventional warm-air drying, which is caused by the high intensity of drying during the removal of bound water. Finally, it can be concluded that the thickness of the dried specimens is a significant factor in the process of high-temperature drying of beech wood INTRODUCTIONWood is the most frequently used material for interior and exterior structures because of its natural and aesthetic aspects and its simple processing. The drying of timber at temperatures above the boiling point of water is called high-temperature drying (Hillis 1984;Aydin and Colakoglu 2005). This technique has attracted considerable attention in recent years. The high-temperature drying of wood is an environmentally friendly method that is three to five times faster than warm-air drying (Trebula and Klement 2002). Drying wood at high temperatures (130 to 150 °C) is an effective method to improve the dimensional stability and biological durability of wood (Perré and Degiovanni 1990, 1999).Based on the cited work, it is reasonable to expect that in the high temperature drying of beech the loss of moisture will be directly proportional to the drying time. When the temperature is raised above 100 °C, the drying time will be shortened, with a faster decrease of moisture content. According to Poncsák et al. (2006), the influence of temperature is more pronounced at higher moisture content. Drying times are short in comparison to conventional warm-air drying, which is attributable to the high intensity of drying during the removal of bound water (Klement and Marko 2009). Kollman (1952) reported that high-temperature drying requires 25 to 60% less energy than does normal kiln-drying. This reduction in energy is attributed primarily to better heat transfer to the PEER-REVIEWED ARTICLE bioresources.com Klement & Huráková (2016). "Beech high-T drying," BioResources 11(2), 5424-5434. 5425wood and less heat loss through the kiln walls because drying time is shortened. The high temperature has a significant influence not only on the discoloration, but also on dimensional stability and mechanical properties of wood. However, the strength and especially toughness therewith is inevitable reduced (Okuyama et al. 1990). Burmester (1975) concludes that high-tempe...