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.
Seventy-six white spruce (Picea glauca (Moench.) Voss) trees were systematically sampled by 30, 40 and 50 cm diameter-at-breast height (DBH) classes from two natural stands in Saskatchewan located near Big River and Candle Lake. Mean ages of the tree samples were 120 and 110 years respectively. Based on sample trees, site indices at breast-height age 50 were 18.5 and 18.1 respectively. Wood basic relative density at breast height was determined for each sample tree by X-ray densitometry and mean values for each tree sample were 0.372 and 0.369 respectively. ANOVA of basic relative density on DBH class (R2= .31) and stand revealed that differences in mean density between stands were not significant. Differences in mean wood density between DBH classes (rate-of-growth) were significant (p = 0.001). Consequently, mean relative density values were determined for the 30, 40 and 50 cm DBH classes for the two tree samples combined. These were 0.387, 0.373 and 0.350 respectively compared to the species average of 0.354. Pith-to-bark density trends were inversely related to ring-width trends, consistent with expectations for white spruce.
Density trends observed in Saskatchewan coincided with those obtained from white spruce trees sampled similarly from three stands in northeastern British Columbia and three stands in north central Alberta. In the BC study, trends in breast-height wood density were reflected in similar and more significant trends in bending modulus of rupture (MOR), bending modulus of elasticity (MOE), MOE in compression, and ultimate compression strength (UCS) of small clear specimens. The combined results of the two previous studies demonstrated robustly that for stands of similar age and site index, wood density and related structural wood properties of white spruce are influenced primarily by rate-of-growth. Pooled results for the two Saskatchewan stands provide further confirmation of this wood density/growth-rate relationship.
Considered within each stand, wood density declined significantly (a = 0.05) as diameter class increased. An exception occurred at Candle Lake. In that stand, lower than expected mean wood density in the 30 cm DBH class resulted in no significant difference between it and the 40 cm class. On review, a similar lack of significant difference in mean density occurred between the 30 and 40 cm DBH classes in two previous samples, one in BC and one in Alberta, but in those stands the density hierarchy remained as expected. One plausible explanation could lie in the fact that these lower than expected density values for small diameter trees coincide with the three lowest site indices of the eight samples. This bears further investigation.
Wood density of Saskatchewan white spruce was higher than that observed in BC and Alberta with even the 50 cm class showing no significant difference from the species average. This suggests that faster growth can be pursued in Saskatchewan before encountering a detrimental reduction in average wood density. Pronounced increases in annual growth rate that occurred after cambial age twenty in the 40 cm and 50 cm trees at the Big River stand corresponded to pronounced declines in breast-height wood density. This was consistent with results observed in two of the previous six samples studied, and strengthens evidence that natural events or silvicultural interventions that result in release will reduce white spruce wood density.
Forintek Canada Corp. created a Building Microbiology Database in 2002 and formed an expert team including an Associate Professor from the University of British Columbia's School of Environmental and Occupational Hygiene. The Database largely contains information from peer-reviewed journals in which there is a link between building materials, microorganisms and health. In response to three questions compiled by the American Forest and Paper Association and Forintek Canada Corp. the Database was searched for information. These questions concerned molds and bluestain fungi growing on wood. The Database does not contain much information on the basic biology of these organisms therefore additional literature was obtained to respond to the questions. The answers, with a scientific rationale for each, are given in this report.
In the most recent edition of the CSA O80 wood preservation standards, retention by assay rather than by gauge was specified for chromated copper arsenate (CCA), ammoniacal copper arsenate, and creosote. Based, in part, on the 14-year data from Forintek's field trials, these assay retentions are lower than the old gauge retentions, and lower than the assay retentions which had been specified in the AWPA standards. The AWPA independently introduced lower retentions for northerly waters in 1995. Continued testing is needed to confirm that the lower retentions will still provide the service life required from marine structures.
The marine tests covered in this report were set up in 1978 in West Vancouver, BC and in 1984 at two sites in New Brunswick. Red pine sapwood coupons were pressure-treated with a range of retentions of preservatives which were listed in the standards at the time. They were suspended in the water column on metal racks and inspected once a year until 2000 at West Vancouver and 1997 at the New Brunswick sites.
At the West Vancouver test site, coupons treated to the recommended assay retention with CCA-C (24 kg/m3) were in excellent condition after 22 years’ exposure. ACA-treated coupons at the recommended assay retention of 30 kg/m3 had failed due to surface degradation by bacteria and fungi. While significant on a thin test coupon, such degradation on a marine pile or timber would have less effect on the strength of the structure. Wrapping the ACA-treated coupons for a period after treatment to simulate the drying rate of large dimension commodities did not improve its performance, nor did using an alternative formulation with a higher proportion of copper. The performance of creosote at above the recommended retention was superior to ACA but significantly inferior to CCA.
Untreated coupons failed in less than a year at West Vancouver and between two and three years at the New Brunswick sites, Shediac Bridge and Whitehead Island. At Whitehead Island, coupons treated to the recommended assay retentions with CCA and ACA were still performing well after 13 and 10 years’ exposure respectively (higher retentions of ACA were added three years after the experiment was set up). However, at Shediac, while CCA-treated samples treated to 24 kg/m3 remained sound, coupons treated to 30 kg/m3 ACA had deteriorated badly after 10 years in test. In contrast, samples treated to close to the recommended retention with creosote performed better at Whitehead Island than at Shediac Bridge.
Interestingly the pressure-treated wood has performed better than the test racks. The racks at West Vancouver, made from 3.5mm thick carbon steel, had moderate corrosion after 10 years and had to be replaced after only 15 years of service.
The overall objective of this study was to better understand the current capacity and the future needs of Saskatchewan's prefabricated and log home industries. Specifically, the project sought to identify the perceived and real limitations to future growth within the industry, and recommend future courses of action required to assist growth within the industry.
The major defining characteristic of lumber cut from trees that have been infected with the mountain pine beetle is the extent of fungal bluestain in the sapwood. Forintek Canada Corp. scientists have previously observed that bluestained wood appears to have different dimensional stability characteristics than non-stained wood when subjected to repeated wetting and drying. Bluestained wood has also been reported to show increased permeability, which may make treatment with liquids such as wood preservatives easier. However, no data is available on how bluestained wood resulting from the beetle attack might affect. We therefore identified the need to generate data on the dimensional stability, checking, and permeability characteristics of bluestained wood compared with non-stained wood.
To examine dimensional stability, specimens of bluestained and non-stained 2 x 4 in. lumber were subjected to wetting/drying cycles. After 5 and 10 cycles, the amount of bow, crook, cupping, twist, and checking was measured. The permeability of the wood was also determined by weighing end-matched specimens before and after a 1-, 4-, and 24-hour dip or after a pressure treatment cycle with chromated copper arsenate preservative, and then calculating the uptake and preservative retention.
The results clearly show that when repeatedly wetted and dried, such as occurs in exterior end uses, bluestained beetle-killed wood is more dimensionally stable (less cupping and twist) and checks less than non-stained sapwood, but is more permeable to water. The stresses appear to be relieved by many micro-checks rather than fewer large checks. Overall, the improved dimensional stability should result in the lumber made from stained wood remaining straighter.
Increased permeability of the bluestained wood was confirmed by data showing enhanced chromated copper arsenate (CCA) uptake and penetration. One implication of the stained sapwood treating more readily than non-stained wood is that in batches of preservative-treated wood, the stained wood is liable to be overtreated or the non-stained wood undertreated. As anticipated, bluestain in the sapwood had no effect on the penetration of preservative into the heartwood, the most refractory part of the wood. Treatment with CCA also masked the bluestain by coloring it green.
The increased permeability probably also has implications for ease of air or kiln drying and possibly reduced degrade in the kiln.
Insects - Attack on trees
Stains - Fungal
Pinus contorta Dougl. var. latifolia - Defects
Preservatives - Permeability
Preservatives - Penetration
Pinus contorta Dougl. var. latifolia - Preservation
The major defining characteristic of lumber cut from trees that have been infected with the mountain pine beetle is the extent of fungal bluestain in the sapwood. It is reported that bluestained wood has shown increased permeability, and questions arose as to whether the application of an adhesive or a finish coating may be adversely affected. Laminating of wood is a key value-added process and one that is very dependent on the quality of the bond between two or more components. Bluestain is a common phenomenon in the secondary wood processing industry where finishing is part of the value-adding process. The finishing evaluations made in this study were intended to benefit these processors.
Pieces of bluestained and non-stained 2 x 4 in. lodgepole pine lumber were dried to a moisture content typically targeted by the furniture sector — i.e., much drier than lumber used for structural purposes. From this lumber, specially constructed edge-glued panels were made which exhibited bluestained to bluestained joints and non-stained to non-stained joints. This construction method provides bluestained and non-stained joints for the laminating tests, as well as providing a good representation of what will really happen in an industrial setting where bluestain most likely will not be separated from non-stain. Each panel was cut in half, with one half being used for the laminating tests and the other half for the finishing evaluations. The strength and durability of the glue lines were measured. Various finish coatings either used alone or in combinations with others were subjectively evaluated.
The laminating tests show that gluelines in lodgepole pine that contains beetle-transmitted bluestain were not significantly different in strength from gluelines in unstained wood when PVA and PRF adhesives are used. The durability of the bluestained beetle-killed wood gluelines easily met the requirements specified by the ASTM D1101 standard.
Where desired, the appearance of bluestained wood can be enhanced or highlighted by a simple standard clear furniture finish. Bluestain in parts of edge-glued panels can be masked if certain types of finishes are employed. The finishes that gave more consistently good masking results were those containing blue, red, and charcoal tints in the stain, toner, or glaze coatings. Increased permeability of the bluestain did not affect the adherence of any of the finishes.
While the finishing evaluations indicate the possibilities for finishing pine, whether it has bluestain or not, market research is recommended, using the best performing finishes on full-scale furniture pieces, to test consumer acceptance.
The extensive outbreak of mountain pine beetle in north central British Columbia is resulting in a large volume of lodgepole pine coming into the log supply for sawmills. The major defining characteristic of beetle-infested trees is the bluestained sapwood caused by fungi carried by the beetle. Because bluestained wood is not very familiar to some consumers, this wood may pose a marketing challenge. Although the non-appearance properties of bluestained wood are widely recognised by the industry as not being compromised, there are no data to support this belief. The literature on other types of bluestained wood reports up to 30% lower impact bending strength (toughness) and higher permeability than for non-bluestained wood.
Forintek Canada Corp. scientists identified the need to generate data on some properties of beetle-killed wood in order to address potential concerns. Approximately 270 pieces each of bluestained lodgepole pine lumber cut from beetle-attacked trees, and equivalent non-bluestained lumber were collected from 14 different sawmills in the B.C. Interior. This was delivered to the Forintek Vancouver laboratory for conditioning and processing into test specimens. The specimens were allocated, in equal proportion from each mill, between tests of mechanical, dimensional stability/permeability, gluing, and finishing properties. The results are presented here and in three associated reports.
This is the first compilation of work on the properties of beetle-transmitted bluestained wood. Overall, the research indicates that this wood can be used, without compromising performance, for structural, furniture, and preservative-treated end uses.
A factsheet summarizing the findings produced for customers of bluestained wood is included in the appendix to this report.
The extensive outbreak of mountain pine beetle in north central British Columbia is resulting in a large volume of lodgepole pine coming into the log supply for sawmills. The major defining characteristic of beetle-infested trees is the bluestained sapwood caused by fungi carried by the beetle. Because bluestained wood is not very familiar to some consumers, this wood may pose a marketing challenge. Although the non-appearance properties of bluestained wood are widely recognised by the industry as not being compromised, there are no data to support this belief. The literature on other types of bluestained wood reports up to 30% lower impact bending strength (toughness) and higher permeability than for non-bluestained wood.
Forintek Canada Corp. scientists identified the need to generate data on some properties of beetle-killed wood in order to address potential concerns. Approximately 270 pieces each of bluestained lodgepole pine lumber cut from beetle-attacked trees, and equivalent non-bluestained lumber were collected from 14 different sawmills in the B.C. Interior. This was delivered to the Forintek Vancouver laboratory for conditioning and processing into test specimens. The specimens were allocated, in equal proportion from each mill, between tests of mechanical, dimensional stability/permeability, gluing, and finishing properties. The results are presented here and in three associated reports.
This is the first compilation of work on the properties of beetle-transmitted bluestained wood. Overall, the research indicates that this wood can be used, without compromising performance, for structural, furniture, and preservative-treated end uses.
A factsheet summarizing the findings produced for customers of bluestained wood is included in the appendix to this report.
