THE PRESSURE TREATMENT OF WOOD WITH SONIC WAVES

Sonic waves were used in the pressure treatment of Douglas-fir and pon derosa pine samples with water, and the results were compared with tho se when the pressure was hydraulically applied, as in conventional tre atments. For Douglas-fir, the sonic treatment was superior to the conv entional treatment at both pressures investigated: 0.55 MPa (80 psi) a nd 0.69 MPa (100 psi). With this species, the sonically induced absorp tions exceeded the hydraulically induced absorptions by an approximate ly constant factor of 1.5 throughout the 2-hour treatment. Continuatio n of this relationship until the Douglas-fir samples reached saturatio n would indicate that sonic waves allow treating solution to gain acce ss to spaces in the wood structure that are unavailable under conditio ns of conventional treatment. This relationship, however, did not exis t with the ponderosa pine samples. In their case, the difference betwe en sonic and hydraulic treatments decreased as the samples approached saturation absorption. The source of this species difference is presen tly unknown. The results indicate that sonic waves may offer significa nt potential for the improvement of the pressure-treating process and the treatment of refractory wood species.