Comparative study between full cell and passive impregnation method of wood preservation for laser incised Douglas fir lumber

In this study, the ability of passive impregnation of Douglas fir (Pseudotsuga menziesii Franco) lumber was compared with a conventional full cell method. With an incising density of 10,000 holes/m² carried out by CO₂ laser, square Douglas fir lumber was treated by both passive impregnation and full cell method for 6 h and 50 min. Different incising densities were also used in passive impregnation to examine the optimum incising density. It was observed that there was no significant difference between these two methods regarding absorption of liquid, moisture content after dipping and penetrated area both at cross and longitudinal sections. However, the value was higher in case of full cell method. Regarding different incising densities, absorption and penetration of liquid was similar for 10,000 and 7,500 holes/m² but it was low for 5,000 holes/m². Therefore, it can be concluded that an incising density of 7,500 holes/m² is the optimum for passive impregnation. The absorption of liquid and its distribution in wood indicates that this non-pressure passive impregnation method can be a good preservation method for impermeable lumber and can be an alternative to full cell method.