Comparing two internal check measurement methods for wood drying quality assessment

Internal checks that are created in the interior of lumber during or after timber drying seriously affect the quality and value of timber used for the production of high value wood products. This study compared two different methods of assessing wood drying quality, by using either an image analysis ImageJ or Digital Calliper technique, to determine the percentage loss of cross section due to internal checking. The study revealed that there was a significant difference in the total area of internal checks, but the overall timber quality classes determined from both techniques were identical based on the Australian and New Zealand standard for timber quality assessment.     

Drying timber in a solar kiln using an intermittent drying schedule of conventional laboratory kiln

The purpose of this study was to apply an intermittent drying schedule developed from a conventional kiln to a solar kiln. Implementing this experiment could help better understand the oscillation of the temperature inside a solar kiln and timber quality during drying progress. The theoretical recharge and discharge curves were used to predict the temperature inside the solar kiln using experimental data obtained previously using a solar kiln. The surface and internal checks were measured using ImageJ freeware, and the development of the Moisture Content (MC) profile was assessed by coring and slicing method for the Eucalyptus delegatensis boards during drying. The results showed that the recharge and discharge model can predict the temperature with less than 2?°C error from the experimental data in the solar kiln. The total drying time to 12% MC was 87?days for the solar kiln. The drying rate was equivalent to the conventional kiln decreasing at an average rate of 0.2% per day. The surface check formation was found when the MC gradient between the core and the case of the board was greater than 42% at 9?days of drying in the solar kiln and conventional laboratory kiln. The applied drying schedule used in the solar kiln was successful and offered similar drying time. However, the oscillation of temperature in the intermittent drying will require further improvement to get closer conditions in a solar kiln.     

Comparing two intermittent drying schedules for timber drying quality

Intermittent drying techniques for drying timber may provide various benefits by improving timber quality and addressing energy efficiency through saving in energy consumption. The purpose of this study was to compare two intermittent drying schedules applied in the treatment of Eucalyptus delegatensis boards, through assessing surface and internal check development, moisture content (MC) profiles during drying, and timber distortions at the end of drying. The study used identical conditions during the heating phase at 45°C/60% relative humidity (RH), except for RH during the nonheating phase (80 and 90%). The results, discussed in this paper, analyzed the timber quality during and at the end of drying. The different RH during the nonheating phase did not generate a significant difference in MC at the case boards between the two drying schedules. The assessed quality of timber at the end of drying was based on AS/NZS 4787:2001. MC gradient, drying stress residual, internal checking and collapse were graded as class “A” (class A is the highest grade and D is the lowest). Bow, cupping, and spring were under the permissible levels based on grading standard AS 2082–2007. Measured data were validated using Drytek® simulation software showing MC movement in case boards.