This project evaluated a number of opportunities to coastal producers related to kiln drying issues such as drying practices related to high-value products, drying with superheated steam vacuum and internal core temperature monitoring for large timbers during the heat-up phase. In summary, this project included several laboratory studies to evaluate the using superheated steam/vacuum (SS/V) for drying 7/8”x 6, green western red cedar lumber, and 8x8 and 5x(5,6,7,8,9,10,12) Douglas-fir timbers. SS/V drying yielded faster drying schedules when compared to the results obtained in industrial conventional kilns. The results obtained from the SS/V drying of WRC indicated the potential benefits of technology for drying specialty products especially when compared to drying times obtained with conventional drying (longer than 7 days). However, the results obtained also emphasize the importance of green sorting that is, sorting prior to drying to optimize drying times and reduce the variation of final moisture content.
For large cross section Douglas-firs the drying times were between 3 and 14 days depending on the severity of the drying schedule and initial moisture content distribution. The influence of moisture content and cross section during the early and late stages of the heating process were evaluated on 5x5, 6x6 and 8x8 Douglas fir timbers. Thermodynamic equilibrium was reached after 20 hours regardless of moisture content or cross section size. The knowledge is intended to be used to design conventional drying schedules for large cross section timbers.