A field test of six millwork preservatives has been ongoing for twenty years, using a simulated window corner, or "Y-joint", as the test unit. Three preservatives provided excellent protection to white pine and white spruce: 5% pentachlorophenol in varsol, phenyl mercury oleate in varsol, and 0.75% oxine copper in varsol.
A transparent coating with long-term performance could help wood maintain its share of residential markets against material substitution and potentially expand markets in recreational property and non-residential buildings. While transparent coatings can be made reasonably resistant to UV some UV likely penetrates to the wood and by necessity clear coatings are transparent to visible light. Visible light can also cause damage over the long term thus the underlying wood needs additional protection. Four novel UV protection systems were tested as pre-treatments on uncoated wood and under three coatings, a water-based film forming coating, a water-based acrylic varnish and a solvent based water repellent. Samples were exposed to natural weathering facing South at 45° at a test site in Gulfport, Mississippi, in collaboration with the USDA Forest Products Laboratory. The test material was inspected every six months for discolouration, mold and stain, coating water repellency, flaking, erosion and cracking and substrate condition. After 24 months exposure, coatings over the combination of UV absorber and lignin stabilizer identified by Stephen Ayer were performing better than the same coatings applied over the combination recommended by Ciba and coatings over both pre-treatments were performing substantially better than controls with no pre-treatment. Projection of fitted curves beyond the data appears to indicate that pretreatment may double the life expectancy of the coating. There was no consistent effect of the synergists on either combination at this time.
A field test of six millwork preservatives has been ongoing for 25 years, using a "Y-joint" as the test unit. Three preservatives provided excellent protection to white pine and white spruce: 5% pentachlorophenol in varsol, phenyl mercury oleate in varsol, and 0.75% oxine copper in varsol.
The biggest obstacle to the enhancement of wood properties through any form of chemical treatment is the impermeability of the heartwood of virtually all Canadian Wood species and their relatively narrow sapwood. Incisors using toothed rollers are commonplace in Canadian treating plants but they are not used for many products due to the detrimental effect on surface appearance. Alternative incising technologies anticipated to have less effects on surface appearance have been investigated over the past 30 years. This report revisits four of these technologies, lasers, needles, water jets and biological incising and evaluates their potential for further investigation based on recent advances in technology. Even using the latest technology, laser incising would be too slow and too expensive for a Canadian treating plant. Needle incising would be too slow but the equipment cost should not be an issue. Water jet treatment would also be too slow and the equipment cost is unknown. Biological incising is a very different approach involving batch processing. The major factor would be the cost of inventory which depends on the duration of incubation yet to be determined.
The absence of commercial facilities to recycle or recover value from wood treated with metal-based wood preservatives at the end of its service life is one of the most significant negative points in the generally positive life cycle analysis of treated wood. Wood treated with carbon-based preservatives (metal-free) may be far easier to recycle or recover value from since the preservatives are relatively vulnerable to thermal, chemical and biological breakdown. As a result they might be destroyed by kraft pulping, combustion or composting of treated wood. The present research evaluates the use of carbon-based preservative-treated wood in these processes.
Kraft pulps produced from wood freshly treated with recommended loadings of carbon-based preservatives contained significant quantities of didecyldimethylammonium carbonate (DDAcarbonate), propiconazole and tebuconazole. However, lower preservative concentration in the wood and intensive pulping may be able to produce pulps without detectable preservatives. The azoles were also detected in significant quantities in the black liquor (DDAcarbonate was not analysed in black liquor).
No azoles were found in the ash produced from combustion, but significant quantities were detected in the filtered smoke. DDAcarbonate was not detected in the filtered smoke. Analysis of DDAcarbonate in ash was inconclusive.
A composting experiment has been set up and is in progress. Data on preservative breakdown during composting is expected next year.
An accelerated decay test was set up to compare the performance of CCA-treated needle-incised white spruce and lodgepole pine heartwood with end-matched conventionally-incised material. Short lengths of 2 x 4 and comparable untreated material were installed in a warmed soil bed in the open air. After 12 years of accelerated exposure (equivalent to 15 years' natural exposure), all the treated material - spruce and lodgepole pine, needle and conventionally incised - was almost completely sound with minor patches of surface decay. In contrast, both the untreated spruce and the untreated lodgepole pine heartwood had failed due to decay. The performance of needle-incised and conventionally-incised lumber has been very similar in both species.
Preservation - Incising - Tests
Picea - Preservation
Pinus contorta Dougl. var. latifolia - Preservation