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Moisture content levels and decay of hemlock
1986 - IRG/WP 1287
As a model of decay conditions of wooden members in wooden houses, a decay test was set up in which samples of western hemlock (Tsuga heterophylla) under 4 moisture levels were examined. Each week the samples were weighed and if the weights indicated that their moisture contents were lower than the expected levels, distilled water was added. Every 8 weeks 3 samples from each condition were oven dried at 60°C for 48 hours, up to 48 weeks. After 48 weeks, 3 samples from each condition were oven dried every 16 weeks. The results obtained were as follows: After examining the samples for 96 weeks at 27°C, the mean weight loss of the hemlock samples kept at about 50-100% moisture content level was larger than those of the other levels. If the samples were dried every 8 weeks, the amount of decay in them was not significant. Decay was also not significant in the samples kept at approximately 20-30% moisture content level.
K Suzuki

Bending properties of treated western hemlock plywood
1996 - IRG/WP 96-40064
This study investigated the mechanical properties of western hemlock plywood after treatment with waterborne preservatives and redrying. Unlike previously reported results for southern pine plywood, western hemlock plywood was more sensitive to redrying temperature than to preservative treatment. Generally, western hemlock plywood was affected by temperature and other variables. Losses in mechanical properties were generally higher than for similarly treated and redried southern pine plywood. Treatment of the plywood with either acidic (CCA-type C) or alkaline (ACZA) solutions resulted in adequate preservative gradients. Western hemlock tended to be affected more by acidic solutions than by alkaline solutions. Based on this research, treated western hemlock plywood should not be redried at temperatures in excess of 60°C without applying some design stress reduction factor.
H M Barnes, A Khouadja, D E Lyon

Leaching of CCA components from treated wood under acidic conditions
1993 - IRG/WP 93-50004
The leaching of CCA components from treated wood under acidic conditions were investigated. Western hemlock treated with three types of CCA and two levels of target retention was subjected to leaching at four different levels of pH. After leaching tests, leached samples were subjected to laboratory decay and soft rot tests. The amount of CCA components leached was dependent on acidity of leaching solution, CCA formulation, and target retention. The leaching of CCA components at pH 4.0 or above was not significant even though a relatively low amounts of arsenic were leached. The resistance of leaching according to the type of CCA was in the sequence of CCA-Type C (oxide), CCA-Type C (salt) and CCA-Type B (oxide). The amount of leaching was increased with the increase in target retention. The reduction of biological effectiveness was not distinct for treated wood leached in acidified water of pH 4.0 or above. Based on the results of this study, it might be concluded that losses of CCA components at pH 4.0 or above were not great enough to cause public concern about environmental problems and reduction of biological efficacy in service.
Jae-Jin Kim, Gyu-Hyeok Kim

Termite-tunnels formation on the surface of termite-resistant wood species in field sites
2001 - IRG/WP 01-10400
In this report, termite-tunnels formation by the subterranean termite, Coptotermes formosanus Shiraki on the surface of termite-resistant wood species, namely, Hinoki (Chamaecyparis abtsu), Yoshino Hinoki (Chamaecyparis abtsu), Miyazaki Hinoki (Chamaecyparis abtsu), Hiba (Chamaecyparis abtsu) and Japanese cedar (Cryptomeria japonica) was conducted in field sites. Westernhemlock (Tsuga heterophylla), Douglas- fir (Pseudotsuga taxifolia) and Ryukyu pine (Pinus luchuensis) were used as the control. 62 The termite-resistant woods species were classified either as heartwood timber (H) or sapwood timber with a heartwood center (S) and also classified based on their prefecture of origin. Otherwise, the termite- resistant wood species for the termite test were examined in using the forms on the surface of all the termite-resistant wood species by the subterranean termite, Coptotermes formosanus Shiraki. It was found that even for termite-resistant wood species treatment with preservative chemicals is required.
Y Kadekaru, K Kinjo, S Yaga

Localized induction of hemlock brownstain by Ophiostoma piceae
1995 - IRG/WP 95-10106
Hemlock brownstain, a coloration disfiguring western hemlock and amabilis fir, causes economic loss in the high-value Canadian export lumber market. Recent work by the author has suggested that wood-sapstaining fungi can induce the formation of brownstain. Ophiostoma piceae, the most frequent staining fungus on western hemlock lumber in B.C., was chosen as a model to investigate fungal participation in the brownstaining process. A technique was developed to enable infection of thin sections and monitoring the induction of brownstain under a microscope. The results demonstrated the development of brown deposits in parenchyma cells penetrated by hyphae. Further research is underway to determine the chemical structure of the brown deposits developing in the presence of Ophiostoma piceae.
B Kreber

Relationship between the bending strength and the degree of termite attacks on western hemlock by Coptotermes formosanus Shiraki
1990 - IRG/WP 1434
For the examination of the relationship between the bending strength and the degree of termite attacks, Western Hemlock (Tsuga heterophylla Sarg.) was used. Sixty specimens (4.5 x 4.5 x 82 cm³) were attacked by termites at the culture room of Coptotermes formosanus Shiraki. The termites were introduced on the central parts (10 cm) of specimens. In the case of the 2 points loading, the bending moment is maximum at these parts. According to the results obtained from this experiment, both the modulus of rupture (MOR) and the modulus of elasticity (MOE) were showed significant against the weight loss (WL) of central parts of the specimens. MOR = 713 - 19.9 WL (n=60, r=-0.73**) MOE = 127800 - 1910 WL (n=60, r=-0.58**)
K Suzuki, T Tanaka

After 18 years, preservative dipping and brush treating continue to provide protection to shingles of western wood species
1997 - IRG/WP 97-30156
The presence of residual preservation in dip-treated and brush-treated shingles of various species from the western United States was assessed 18 years after installation using Aspergillus bioassays. The performance of western redcedar (Thuja plicata) was compared to western hemlock (Tsuga heterophylla), sugar pine (Pinus lambertiana) and western larch (Larix occidentalis). Untreated shingles of all four species were seriously decayed, while those receiving topical treatments continued to maintain their appearance. Bioassays from the shingles indicated that residual pentachlorophenol and chromated copper arsenate were still present on both upper and lower surfaces. The results illustrate the benefits of topical treatments for protecting wood in above ground exposures.
T C Scheffer, D J Miller, J J Morrell

Specifying preservative-treated resistant timber: Conforming to European Standards
2001 - IRG/WP 01-20235
The most common construction timbers used in the UK are of low natural durability and, generally, resistant to preservative treatment. These include species of spruce, hemlock and fir. However, their characteristically limited and non-uniform uptake of preservatives may still confer sufficient protection to give satisfactory durability performance in terms of biological resistance. This paper describes the results of a study investigating the protective efficacy of treatments defined according to the approach in European Standard EN 351-1 when penetration and retention values are used in timbers showing non- uniform treatment characteristics. The data show that variation between batches of samples is high for preservative uptake, retention and penetration. The biological data have given indications that this leads to differences in performance effectiveness. However, the bioassay method developed does not in its present form, sufficiently discriminate between treatment/species combinations.
E D Suttie, A F Bravery, T B Dearling

Three-year field test of preservative-treated Canadian species in Korea
2014 - IRG/WP 14-30646
The purpose of this study was to generate field performance data in Korea on Canadian softwood species preservative-treated to Canadian standards. Two field tests of preservative-treated Canadian softwood species, one in ground contact and one above ground, were installed in Jinju, Korea in November 2010. Western hemlock and white spruce were incised and pressure-treated with alkaline copper quaternary (ACQ) or copper azole (CA), based on the Canadian CSA O80 Series-08 standards. End-matched material for ground contact exposure only was also installed in September 2011 at a field test site in Canada. After three years of exposure in Korea and two years in Canada, no decay was found in preservative-treated samples at either test site, while in untreated material decay, and particularly termite attack in Korea, were well advanced.
Jieying Wang, Jong Bum Ra, P I Morris

A Treatability Study of Western Wood Species with Water Based Azoles and Insecticides Using Buffered Amine Oxides
2016 - IRG/WP 16-40766
The use of Western U.S. Wood Species remains small in today’s global wood product market when compared to the use of other commercially available softwoods. One reason that other fiber sources, those that may be less naturally durable or exhibit slightly inferior mechanical properties, are utilized is ease of treatment. In an attempt to ensure adequate penetration in commercially important and difficult-to-treat Western Wood Species such as Douglas fir, Hem fir, and 100% Heart Redwood, the use of deep incisions is standard practice. The development of solvent-free, Water Based Buffered Amine Oxide Treatment Systems (known commercially as TRU-CORE® Technology) for use in wood preservation has allowed significant modernization of the application and preservation process for these species. Important to the future growth of Western Wood Species may be the elimination of incising. When the Buffered Amine Oxide Treatment System technology is utilized it has been demonstrated that non-incised difficult-to-treat species are fully penetrated in the sapwood and heartwood. The buffered amine oxides allow for a chemically based infusion process that is capable of delivering key wood protectants completely throughout the wood. This water based system imparts a minimal amount of added moisture into the wood during the process, so there is no need to dry after treatment. To date, there are over 50 commercially successful Buffered Amine Oxide Treatment Systems. In 2015, over 4,000,000 m3 (1.695 billion board feet) of wood was treated with the Buffered Amine Oxide System.
R W Clawson Jr, C N Cheeks, K A Cutler

Durability of thermally modified western hemlock lumber against wood decay fungi
2022 - IRG/WP 22-40954
The chemical modification of wood is gaining popularity as a treatment to increase wood durability in the United States. Further standardization and testing of thermally modified North American species is needed to optimize the production of thermally modified products from regionally available resources. This work measures the impact of thermal modification of western hemlock lumber durability against decay fungi for a single treatment process. Western hemlock lumber was thermally modified using a cycle with temperatures ranging from 80-170ºC and was cut into standard 19 mm blocks for testing according to AWPA method E10. Performance of thermally modified wood was measured against two brown rot fungi, Rhodonia placenta and Gloeophyllum trabeum and one white rot fungus, Trametes versicolor over an 8, 12 and 16-week incubation period. Unmodified western hemlock wood, untreated southern pine and copper azole-treated southern pine were included for comparison. Thermal modification resulted in a slight improvement in durability against Gloeophyllum trabeum, but not Rhodonia placenta compared to untreated western hemlock which caused 50.3% and 52.2% mass loss in thermally modified western hemlock after 16 weeks, respectively. T. versicolor caused a 21.2% mass loss after 16 weeks, but this value was not statistically different than untreated western hemlock (p=0.46). For comparison, copper azole-treated southern pine showed only an average of 0% and 15% mass loss when exposed to G. trabeum or R. placenta for 16 weeks, respectively. Together, these data indicate that while there may be some protective effect of thermally modifying western hemlock, further development of treatment processes are needed to improve the durability of thermally modified western hemlock. This study describes durability testing of thermally modified, Tsuga heterophylla (western hemlock) wood using an American Wood Protection Association (AWPA) E10 soil bottle test (AWPA 2020). The test used 19 mm blocks cut from the thermally modified and control western hemlock lumber that was left over following bending strength tests. The test compared the decay resistance of thermally modified western hemlock with untreated western hemlock, untreated southern pine, and southern pine treated with copper azole to UC3B retention levels against two brown rot fungi and one white rot fungus.
G Presley, J Cappellazzi, I Eastin