Microwave (MW) treatment of wood has been evaluated in recent years for different purposes by several scientists. Microwave conditioning improves permeability, reduces density and heat conductivity and changes dimensional stability. Furthermore, it could even improve the permeability of refractory wood species such as spruce and Douglas fir. In this study, MW pre-treatment was applied to spruce wood samples. Spruce wood samples at 60% initial moisture content (MC) were pre-treated using MW Owen for 5, 5.5, 6 min, respectively. The intensity of MW was kept constant at 800 W for all variations. Pre-treated spruce wood samples were then impregnated with 1.5% CCA solution by applying initial vacuum for 20 min and then pressure for 30 min. The retention levels and penetration depths were determined for each variation and control samples. The MW pre-treatment increased the retention levels and penetration depths. It was found that the retention levels were 5.37, 6.04 and 6.18 kg/cm3 for the samples exposed to MW pre-treatment for 5, 5.5, and 6 min, respectively. The retention level for control wood samples was 3.64 kg/cm3. The results showed that MW pre-treatment enhanced the impregnation properties of spruce wood. In addition, the applied MW pre-treatment reduced the modulus of elasticity (MOE), modulus of rapture (MOR) and compression strength parallel to grain values (CS).

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