Marine Exposure Tests of Pressure-Treated Douglas Fir and Southern Pine

Dried lumber pieces of Douglas fir heartwood and sapwood and southern pine sapwood (3/4 by 3 by 18 in.) were treated by the full-cell process with creosote and creosote — coal tar in a 70-30 per cent solution. Douglas fir sapwood pieces also were treated with ammoniacal copper arsenite (Chemonite) and with copper formate. Average retentions in pounds per cubic foot were: creosote, 35.7; creosote — coal tar, 33.7; Chemonite, 0.38; and copper formate, 0.28. Specimens were installed during the summer and fall of 1957 at three marine exposure sites on the Pacific Coast and three sites on the Atlantic Coast of the United States. Douglas fir sapwood pieces treated with each preservative were installed at all sites. Douglas fir heartwood pieces were installed at three Pacific Coast sites and one Atlantic Coast site. Pine specimens were installed at two Atlantic Coast sites. Specimens were mounted on galvanized steel bars in replicates of five. Pieces treated with creosote and creosote — coal tar were mounted on bars numbered 1 through 5 in such a way that each bar contained a complete set of treated replicates and two untreated panels. Bars 6 and 7 contained five replicates of pieces treated with Chemonite and with copper formate, respectively. One bar of specimens treated with creosote and creosote — coal tar, and one replicate from both bars 6 and 7 will be removed permanently every two years. These specimens will be examined closely and related according to a standard procedure as to extent and cause of deterioration. Results of the first biennial inspection are reported.