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.