J Wood Sci (2014) 60:243–248 DOI 10.1007/s10086-014-1399-x ORIGINAL ARTICLE Surface quality and hardness of eastern redcedar as function of steaming Bulent Kaygin • Kucuk Huseyin Koc • Salim Hiziroglu Received: 11 December 2013 / Accepted: 9 April 2014 / Published online: 6 May 2014 Ó The Japan Wood Research Society 2014 Abstract The objective of this study was to evaluate Keywords Roughness Á Hardness Á Eastern redcedar Á influence of steam treatment on surface quality and hard- Electron scanning microscopy ness of eastern redcedar (Juniperus virginiana L.). Defect- free samples with dimensions of 40 mm by 50 mm in by 20 mm were used for the tests. Specimens were exposed to Introduction steam having a temperature of 130 °C for 1-h and 3-h periods of time. Surface roughness of the samples at initial Modification of wood and wood-based materials using and exposed conditions was determined using stylus type different techniques is getting more popular to improve equipment across the grain orientation on tangential sur- overall quality of the final product. For example, heat face of each sample. Janka hardness of the control and treatment is one of the most commonly used modification treated samples was also determined on Comten testing processes to enhance properties of different wood species. system. Based on the findings in this work, no significance Generally heat treatment does not require addition of any was found between surface roughness values of the spec- chemicals into the wood to change its characteristics. Heat imens steamed for 1 and 3 h. However, both types of treatment of wood has attracted substantial interest in steamed specimens had higher average roughness values North America having raw material with improved prop- ranging from 52 and 60 % than those of control samples. It erties for different applications including flooring, siding, appears that 3-h steaming adversely influenced hardness of kitchen cabinets and windows. Main idea behind heat the samples reducing its 9 % as compared to those of treatment is to enhance dimensional stability and change control samples. Densification effect of steaming on the the color of the final product so that they can be used more samples was also evaluated using scanning electron effectively during their service life. However, mechanical microscope (SEM) and it was determined that steaming properties of wood are adversely influenced as a result of had some crushing effect on the cell wall. heat treatment process. As it is well known the main objective of modification of properties of wood is to enhance their physical and mechanical characteristics [1– & B. Kaygin ( ) 6]. In addition to heat treatment, steaming among the Forestry Faculty, Department of Forest Industry Engineering, Bartin University, 74100 Bartin, Turkey various methods is considered as one of the most envi- e-mail: [email protected] ronmentally friendly one since no chemicals or any addi- tives involve with the process similar to heat treatment. K. H. Koc Steaming of wood has been used for many years to Forestry Faculty, Department of Forest Products Engineering, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, Turkey change its color, to bend the wood for different applica- e-mail: [email protected] tions [7, 8]. For example, steam bending of wood is very popular to consume less material so that resource can be S. Hiziroglu used efficiently. Overall steaming process depends on Department of Natural Resources Ecology and Management, Oklahoma State University, Stillwater, OK 74078-6013, USA species, size and configuration of the place. It is suggested e-mail: [email protected] that overall steaming time could be set as 1 h for every 123 244 J Wood Sci (2014) 60:243–248 25-mm thickness of the member [9–12]. Steaming is finishing material used are two parameters directly related widely applied to European beech to change its color for to surface quality of the raw material. Although different furniture and flooring manufacture. Some of the physical properties of eastern redcedar have been investigated there and mechanical properties of steam-treated European is only poor information on surface quality and hardness of beech were determined by Yilgor et al. [11]. It was this species as function of steam treatment. The steam is determined that 100-h steaming reduced compression effective on the wooden surface. Therefore, the objective strength and modulus of elasticity of the samples 13.3 and of this work is to evaluate eastern redcedar samples within 16.5 %, respectively [11]. It is important to determine both the scope of such approach so that data from this study hardness and surface quality of steamed wood since they could possibly be employed as a quality control (glossi- are widely used for flooring [9, 13]. The hardness of ness, hardness, adhesion, finishing tests) tool to use eastern steamed samples from different hardwood has been redcedar more efficiently in further manufacturing steps. investigated in various studies [9, 13–16]. It was concluded that overall hardness of the specimens from both softwood and hardwood species reduced due to steaming. Hardness Materials and methods values of wood samples steamed at different conditions were also investigated employing Brinell and Janka hard- Defect-free eastern redcedar samples with width of 40 mm, ness method in a previous study [9]. length of 50 mm and thickness of 20 mm were used for the Eastern redcedar (Juniperus virginiana L.) is one of the experiments. A total of 60 specimens were conditioned in a widely distributed indigenous conifers in Oklahoma. Over room with temperature of 20 °C and a relative humidity of four million hectares of Oklahoma lands are infested with 65 % until they reach 12 % equilibrium moisture content. redcedar, primarily in the eastern part of the state. How- Next, tangential surfaces of the samples were sanded with ever, in recent decades the trees have begun to take over 150 grit sand paper applying six light strokes. Including the tall grass prairies and plain lands of north central and control samples, six types of samples were prepared to western Oklahoma. Use of low-quality eastern redcedar as evaluate their surface roughness and hardness characteris- a raw material in lumber manufacturing is not substantial tics as function of steaming. due to its low value and irregular growth pattern. There- As experimental schedule displayed in Table 1, sam- fore, eastern redcedar is a nuisance to farmers and ranchers ples were exposed to steam for 1 and 3 h following who often lose crop and pasture land to the species. Many natural drying in room conditions for 2 weeks as well as wildlife species that need open range also are affected drying in a laboratory type kiln at a temperature of negatively by this species [17–20]. Eastern redcedar also 110 °C for 1 h. Dimensions and weight of each sample tends to be very aggressive in areas where naturally occurring range fires have been suppressed. Although most Table 1 Experimental schedule of western Oklahoma’s eastern redcedar is of poor quality, Sample type Experimental process Number of sample range-grown trees are not efficient for lumber manufac- turing, while some of eastern Oklahoma’s forested lands A Control samples 10 produce redcedar suitable for lumber production [19–21]. B Kiln dry 10 Experimental panels such as particleboard from whole-tree C Dried after 1-h steaming 10 chipped eastern redcedar were manufactured in a previous D Kiln dried after 1-h steaming 10 study [22, 23]. It appeared that physical and mechanical E Dried after 3-h steaming 10 properties of the panels were comparable to the panels F Kiln dried after 3-h steaming 10 made from other wood species and foliage content in the panels did not reduce their properties substantially [23]. Based on the results of this study, low-quality redcedar trees had a potential as whole-tree chipped furnish for manufacturing particleboard [22]. Properties of eastern redcedar exposed to heat treatment schedules have been investigated in several studies [17, 18]. It was found that shear strength of heat-treated samples was adversely influenced by such process while their dimensional stability enhanced. The surface quality of wood and wood-based materials plays an important role to have final products with accepted cost and customer satisfaction. Sanding and amount of Fig. 1 Control and 3-h steamed eastern redcedar samples 123 J Wood Sci (2014) 60:243–248 245 Fig. 2 Typical surface roughness profiles of the samples were also determined at accuracy levels of 0.10 mm and Table 2 Surface roughness and Janka hardness values of the samples 0.10 g to calculate their density. Steaming process of the Sample Density Roughness Janka samples was carried out in stainless steel container heated type (g/cm3) parameters (lm) hardness (kg) up to create steam with a temperature of 130 °C. Figure 1 R R illustrates control and steam samples. Surface quality of a z the samples at each exposure process along with control A 0.482 4.65 (0.73)a 44.39 (5.76) 379 (39.60) samples was evaluated employing a fine stylus type pro- B 0.491 5.03 (0.75) 34.49 (6.74) 373 (39.40) filometer T-500 Hommel Unit. A total of three random C 0.479 7.06 (0.76) 48.66 (6.68) 399 (34.32) measurements were taken using a tracing span of 15 mm. D 0.471 7.33 (0.80) 49.48 (7.01) 409 (28.59) The stylus profilometer, Hommel T-500 Unit equipped E 0.470 7.34 (0.68) 49.24 (7.89) 345 (30.01) with a Tk-300 skid type pick-up resulted in two roughness F 0.463 7.43 (0.76) 51.34 (6.79) 355 (29.56) parameters, namely average roughness (R ) and mean a a Numbers in parentheses are standard deviation values peak-to-valley height (Rz).