An ammoniacal copper arsenic preservative, copper-arsenic-additive (developed at the Eastern Forest Products Laboratory for difficult-to-penetrate wood species), was tested in a commercial treating plant using white spruce (Picea glauca [Moench] Voss) poles and lumber. The treatment schedule comprised steaming followed by a full-cell treatment. The ammoniacal solution, containing 3.2 percent oxides, was heated fro 46C (115F) to 66C (150F) during the first 3 hours of increased pressure (860 kPa; 125 pounds per square inch) then either left to cool for 10 hours or rapidly cooled with water for 3 hours.
An ammoniacal preservative, copper-zinc-arsenic-additive (developed at the Eastern Forest Products Laboratory for difficult-to-treat wood species), was tested in a commercial treating plant using poles, posts, and lumber of white spruce (Picea glauca [Moench] Voss). The treatment schedule comprised steaming for 5 hours followed by a standard full-cell treatment with a solution containing 2.2 percent oxides and 6 percent ammonia heated to 35C (95F). A pressure near 860 kPa (125 pounds per square inch) was maintained for 10-15 hours.
Two ammoniacal preservatives, copper-arsenic-additive (CCA) and copper-zinc-arsenic-additive (CZAA) - developed at the Eastern Forest Products Laboratory for difficult-to-penetrate wood species - were tested in a commercial treating plant on Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plywood. The inner plies were spruce (Picea sp.) fir (Abies sp.), and hemlock (Tsuga sp.) - all can be difficult to penetrate with aqueous solutions. The treatment schedule comprised steaming for 1.5 or 2.75 h followed by a standard full-cell treatment for 1.5 or 4h (the longer schedule was used with CZAA). There was little strength loss due to treatment and no evidence of wood collapse. Cores taken from the center of the plywood faces showed: (1) the preservative had penetrated all 5 plies; (2) plywood treated with a 3.2 percent oxides solution of CAA retained 9.3 kg/m3 (0.58 pounds per cubic foot) oxides; and (3) plywood treated with a 2.2 percent oxides solution of CZAA retained 9.9 kg/m3 (0.62 pounds per cubic foot) oxides.
Stakes of various wood species as well as composite material of different species (plywood) were pressure-treated using a variety of preservatives and chemical loadings. Each stake is buried to half its length at the Petawawa Forest Experiment Station -- near Chalk River, Ontario. The oldest stakes in the plot are treated with copper abietate/pole oil and after 21 years all of the stakes are still performing well. Red pine stakes treated with copper chrome arsenate type B are also performing well after 19 years of service. Performance of the stakes is monitored yearly by examining each stake and assigning a rating according to the severity of decay present. Performances of the treated stakes are compared to untreated controls of the same species installed in the same plot. Preservative effectiveness is expressed as the average number of years in service over the percent stakes remaining in service at the time of examination. One hundred and twenty seven series of stakes are currently under test. Stakes treated with zinc thiocyanate and zinc thiocyanate/latex are performing better than expected to date.
Service records of treated fence posts installed at the Petawawa forest experiment station at Chalk River, Ontarion have been compiled periodically since 1937 to evaluate the effectiveness of various wood preservatives. Untreated control posts of non-durable Eastern Canadian species had an average service life of from 3.0 to 8.3 years. A number of simple application processes as well as pressure treatments have proved to be very effective as indicated in the service life data presented. Posts of 20 species treated full length by the creosote thermal process are in remarkably good condition after 43 years. Those treated (to 36 inch height) were generally sound at the groundline but their tops were degraded after 18 to 25 years. Simple processes such as cold soaking, sap displacement and diffusion methods produced a service life of over 20 years with various wood species and preservative combinations. Some series of posts treated with copper chrome arsenate have attained a service life of 20 years with all of the posts remaining in service to 1980.