Permeability of Douglas-Fir in Oregon

Three Douglas-fir heartwood studs were collected from 29 Oregon mills during 1958 and the heartwood and sapwood from 18 other mills in 1959. In 1958, paired test specimens 1.2 inch by 1.2 inch by 6 inch were conditioned at 90?F. to a moisture content of 8 percent, one tested for creosote impregnation, the other for water impregnation. The 1959 test material was used for air permeability flow and for permeability tests of creosote and copper sulfate water solution. Air flow was measured by special equipment with air pressure of 20 lbs. on 0.625 inch diameter on end grain and 1 inch of length. Determination was of cc. of air flowing through apparatus in 1 second. Penetration of preservative was by 100 psi of pressure in solution for 30 minutes. Temperature used in 1958 was 170?F. for creosote and 70?F. for water. 1959 tests with creosote and 10 percent solution of copper sulfate were at 120?F. Rate of air flow was not directly correlated with creosote penetrability but extremes could be detected. Generally, heartwood from western Oregon is more easily treated than heartwood from northern Oregon. Sapwood is more treatable than heartwood generally but some sapwood was less permeable than heartwood from other sources. Copper sulfate usually penetrated more deeply in heartwood than creosote. Differences in gross anatomical features were not indicative of differences in permeability.

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