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Comparative studies on the moisture performance and durability of wooden facades
2012 - IRG/WP 12-20492
Wooden claddings are traditionally used in many parts of the world. Also modern structures are frequently made from timber and timber engineering panel products. However, wood has to compete with other cladding materials and its durability needs to assure sufficient functional and aesthetic service life. Besides many other factors the durability of a wooden facade is dominated by its moisture performance on the one hand and the occurring moisture loads on the other hand. Within this study continuous wood moisture content measurements were conducted on three different test objects: 1. Combined facade-decking elements made from eleven different wood species relevant for the European market were exposed to the South and to the North in Hannover, Germany. Material-specific moisture performance was evaluated and compared with climatic parameters. 2. Three-years of measurements were carried out on the walls of a timber-made test house at the same test site. Measurements were made in different wood species, at different distances to the ground and in all four compass directions. 3. The effect of different roof overhangs on the moisture load of a wooden facade made from Norway spruce was studied on a test assembly in Tåstrup, Denmark. In addition to the moisture content measurements, wood temperature was recorded daily and relevant weather parameters were collected from meteorological stations nearby. To assess the respective moisture performance of the various materials and construction related parameters, the number of wet days was determined and a performance model was applied to all data sets. Based on a model for above ground decay the expected service life was calculated for different exposures, materials and design details. The highest moisture loads were found on the West facade, which is the weather side in Central Europe, followed by the North facade, where re-drying was inhibited due to limited solar irradiation. Furthermore the splash water zone was clearly identified, where moisture loads were increased and re-drying reduced due to lower wind speeds close to the ground. Finally, the moisture performance of the various timber species differed significantly. Thus, a wide range of service life estimates was deviated from the data sets.
T Bornemann, C Brischke, J-M Lück

Service life prediction of wooden components – Part 2: Impact of material, exposure and design details
2010 - IRG/WP 10-20440
Dose-response functions permit to estimate the moisture and temperature induced decay potential for any wooden building component and exposure, and thus the service life to be expected. In part 1 of this series dose-response functions were established as a result of double layer field trials carried out at 24 European test sites over up to eight years. Using them makes it no longer necessary to conduct field trials as long as decay actually occurs. They allow determining dose-time functions for a certain construction detail over shortened time periods (2 3 years). Within this paper we present the test set up of different studies aiming on quantifying the impact of material, exposure and design details on the service life to be expected for wooden components. Therefore long-term moisture recordings were applied to different wooden commodities, e. g. fence posts, pickets, decking, and facades. Furthermore, the impact of orientation, distance to the ground, and driving rain load on facade panels was studied. Finally dose-time functions will be recorded for ten different wood species used in horizontal and vertical orientation. First results from the various studies including preliminary service life estimation for various components are also presented.
C Brischke, B Lauenstein, M Bilstein, T Bornemann, A O Rapp

Wood preservatives: Field tests out of ground contact. Brief survey of principles and methodology
1976 - IRG/WP 269
This paper contains the following spots: 1.: The general need for field tests. 2.: Interests and limits of field tests in ground contact. 3.: Various methods in use for out-of-ground contact field tests. 4.: Fungal cellar tests are they an alternative to above-ground decay exposure tests? 5.: Conclusions.
M Fougerousse

A note on testing the efficacy of wood preservatives above ground
1995 - IRG/WP 95-20078
A number of test methods have been used to evaluate the performance of wood preservatives in above ground situations. These have included EN 113 tests following natural exposure weathering (NEWT), L-joint or T-joint tests, lap-joint tests, and decking tests. A new test referred to as the A-frame test has been developed and is under evaluation. This is based on a sandwich-type test in which a thin (3.5 mm) sample is exposed outdoors between two untreated samples on a rack or A-frame. The advantages and disadvantages of these types of tests are discussed in a short note.
G R Williams, J A Drysdale, R F Fox

Finite element analysis of boron diffusion in wooden poles
2003 - IRG/WP 03-40263
The problem of describing the migration of dissolved boron in wood is treated with special reference to the commonly used remedial treatment of wooden poles. The governing equations are derived and discussed together with some of the material parameters required. The equations are solved by the finite element method and finally, results showing the effect of different treatment strategies are presented.
K Krabbenhøft, P Hoffmeyer, C G Bechgaard, L Damkilde

Visualization of inorganic element distribution in preservative treated wood by SEM-EDXA
2001 - IRG/WP 01-40208
SEM-EDXA was found to be an effective way of visualizing inorganic element distribution in wood as it was possible to examine some inorganic elements at the same time and map the concentration differences in color. Japanese cedar sapwoods were impregnated by vacuum treatment with CuAz or by pressure treatment with CCA preservatives and then distribution of Cu, Cr and As elements in wood were examined by SEM-EDXA. For sapwood treated by CuAz, Cu element was more distributed in latewood tracheids near growth ring boundary, axial parenchyma cells (resin cells) and ray parenchyma cells. Sapwood treated by CCA seemed to have the same distribution of Cu as sapwood treated by CuAz. In resin cells, a lot of crystalline deposits were fringed with CuAz and CCA preservatives. This may indicate predominant interactions between preservatives and chemical constituents of the parenchyma cells.
H Matsunaga, R Matsumura, K Oda

Fungal colonization of CCA-treated decking
2003 - IRG/WP 03-10491
The identification of fungi isolated from CCA treated decking in Vancouver is reported. About two thousands locations were sampled from over sixty boards recovered from six decks. Wood chips from each location were placed onto four different types of media. Of the large number of isolates obtained, around 15% were obtained from the interior of the boards. The succession of colonization in CCA-treated decking; i.e. bacteria, mould, staining fungi, (soft-rot fungi), and basidiomycetes, was similar to that reported from untreated wood exposed above ground and from CCA treated wood in ground contact. The percent frequency of isolation around checks was higher than that from wood just below the treated surface. In the case of boards where decayed wood was observed during sampling, most decay was associated with checks. In this study, Gloeophyllum sepiarium and Gloeophyllum trabeum (tentatively identified) were the only decay basidiomycetes isolated from the inner wood of decayed decking. Other unidentified basidiomycetes were isolated from the treated surface of the boards, the check surfaces or the cut end of decking from both decayed and non-decayed boards.
S Choi, J N R Ruddick, P I Morris

Performance of non-incised CCA-treated hem-fir decking
1993 - IRG/WP 93-40004
The question of what preservative penetration will provide an acceptable service life for treated wood in residential above-ground applications is topical in North American standards committees. Non-incised CCA-treated nominal 2 x 4 inch² hem-fir decking with penetrations close to the proposed CSA O80 2 decking standard of 80% over 5 mm, has remained without decay after 10 years exposure in south western British Columbia. Material with minimal preservative penetration showed early signs of decay. In contrast untreated unstained material had reached a rating of 1.1 on a 0 to 4 scale (0 = sound) with 12% of boards needing replacement. These results support consideration of a reduced penetration requirement in the standards for CCA treated decking.
P I Morris, J N R Ruddick

Above-ground field tests undertaken in New Zealand
1995 - IRG/WP 95-20063
In addition to "standard" L-joints, above-ground test material exposed at the NZ FRI test site includes treated and untreated decking units, Y-joints, fence battens and weatherboards either with or without additional protection from surface coatings. The latter tests bridge the gap between "model" test assemblies, such as L-joints, and services tests. Most tests are of preservative-treated radiata pine using proprietary formulations which were approved for above ground use at the time when each test was established. Other tests are natural durability tests to determine the suitability of those species, in terms of durability and mechanical properties, for above ground use without preservative treatment. The first tests were established in 1952 and results from those and subsequent tests have been used during periodic amendments to NZ wood preservation standards and specifications. The purpose of the different tests is described as well as pertinent results from them to illustrate their value.
M E Hedley, D R Page, J B Foster, B E Patterson

Service life of pressure treated deckings of spruce in direct contact with the ground
1988 - IRG/WP 3463
For decking outdoors in Sweden, pressure treated Scots pine (Pinus sylvestris L.) is used, on account of its treatability. The feasibility of using instead the refractory Norway spruce (Picea abies Karst.) is tested in a field trial. The spruce decks were treated together with pine decks with an ordinary Bethell process. As yet, after more than four years of exposure, neither in the battens nor in the slats of the treated spruce decks any visible sign of decay has been observed. The status of the deckings is followed up with observations of the moisture content and with Pilodyn measurements of the depth of penetration of the striker pin. The pressure treated spruce material has a consistently lower moisture content and mostly also a lower penetration depth of the Pilodyn striker pin than other untreated material.
J B Boutelje, T Sebring

The possible role of mobile CCA components in preventing spore germination in checked surfaces, in treated wood exposed above ground
2001 - IRG/WP 01-30263
Untreated check surfaces are often exposed in CCA-treated lumber of refractory species used above ground since, during weathering, some checks develop beyond the preservative penetrated zone. However, decay is seldom observed in these checks even after many years of exposure. It is hypothesized that minor amounts of mobile CCA preservative components redistribute during weathering into checks, and that this 'surface treatment' prevents fungal spores washed into checks from germinating and causing decay. A substantial amount of copper was found on the exposed check and end-cut surface in exposed wood through the current research, and whether spores are prevented from germinating by this amount of chemical is being studied.
S Choi, J N R Ruddick, P I Morris

Premature failure of treated timber in wharfs in Papua New Guinea, attributed to defects in design
1991 - IRG/WP 4158
The performance of timber in wharfs in Papua New Guinea has been monitored for a number of years. Premature failure of wharf structures was found in many cases to be due to defects in design rather than ineffective preservative treatment. Above-water timbers were found to be prone to severe checking followed by decay. Protection for the end grain of pile tops and the limiting of radial checking in them was found to be vital. Removable metal caps and stout metal bands sized to give a snug fit around the circumference of the pile were found to give the best protection. Major areas of decay or marine borer attack were most common where other structures were attached to the piles in such a fashion that the "envelope" of treated sapwood was breached. In order for treated timber to perform satisfactorily in wharfs, care has to be taken at the design stage. Any post-treatment machining should be undertaken with suitable tools and remedial treatment or protective measures will be required. A list of recommendations for the use of treated timber in wharfs in the tropics is given, relating to the preparation of wood, the construction of the wharf and the protection of vulnerable parts of the installed wharf. The question of good and bad design, and its effect on service life of wharf timbers requires further investigation. The author requests colleagues with information relating to this to contact him.
S M Cragg

Characterization of checks and cracks on the surface of weathered wood
2000 - IRG/WP 00-40153
The surface roughness of unweathered and untreated pine; unweathered copper chromium arsenate type C (CCA) - treated pine; weathered CCA-treated pine; and weathered CCA-plus-water-repellent (WR) - treated pine was evaluated by a stylus tracing method. Surface roughness parameters Ra, Rz, Rmax, Rk, Rpk, and Rvk were measured. Ra, Rpk, and Rvk were the most appropriate parameters for describing modifications on the wood surface. Ratios of the roughness parameters of the exposed (top) and unexposed (bottom) surfaces of the untreated, CCA-treated, and CCA + WR - treated wood samples were used to estimate the extent of the weathering damage on the exposed surface. The parameter ratios for the top and bottom surface were used to estimate the extent of the damage created by rain and sunlight on each piece of wood. This study shows that the stylus technique is appropriate to estimate the number and size of checks and cracks on wood surfaces after weathering.
D P Kamdem, Jun Zhang

Leaching of preservative components from pine decking treated with CCA and copper azole, and interactions of leachates with soils
2001 - IRG/WP 01-50171
Radiata pine decking was treated with CCA and copper azole preservatives to Australian H3 retention using conventional and modified Bethel schedules, and air-dried. Treated decking boards and durable hardwood controls were subjected to leaching in weather-exposed decks, and matching 19mm cubes were leached in extended AWPA E11-97 lab tests. Deck runoff and E11 leachate water was analysed after rain events and E11 change points. After 10 months, decks had lost up to 700mg Cu, 175mg Cr, 600mg As, 750mg B, 10 mg tebuconazole or 18000 mg tannin per square meter of deck, but flux rates had not yet reached zero for any component. Leaching from E11-97 blocks was much faster and greater than from the decks. Extending the leach period from 14 days to 50 days increased the amount of leaching by up to 40%. Even after 50 days, flux rates were measurable for most components. Deck leachates were applied to three soils using the draft OECD soil leaching column procedure. After elution, the soil was segmented and analysed. Although boron was more mobile than others, components tended to be retained in the topmost (first contacted) layer.
M J Kennedy, P A Collins

Evaluation of teak sawdayst Tectona grandis L Fil as a potential source to obtain a natural wood preservative in Colombia
2004 - IRG/WP 04-30356
Plantation Teak (Tectona grandis L. Fil) has been tested as a possible source of natural wood preservatives due to the known excellent durability of old-growth teak wood. Field tests (ground proximity termite and above ground simulated decking exposures) were established in Colombia in April 2003 at two different test sites with different climates (Tropical Dry and Rain forest). Teak heartwood extracts were obtained using Soxhlet extraction with chloroform-methanol and methanol-ethanol as solvents, for two different mixtures at three different concentrations. Sapwood stakes of Patula pine (Pinus patula) and Globulos eucalyptus (Eucalyptus globulus) were vacuum pressure impregnated with these extracts, and control stakes were impregnated with CCA Type C and ACQ Type D at two nominal retentions (1 and 4kg/m3). The test sites have been found to be very active for both decay and termites. After only 9 months exposure termite attack has been observed from four species (Nasutitermes, Heterotermes, Triangularitermes, Velocitermes), and several basidiomycetes fungi have also been isolated from the test samples (Trametes, Schisophyllum, Poria). The results show that up to 100% of the samples have been subject to fungal attack, although in most samples only superficial trace attack has occurred in the exposure period. In contrast, termite attack has been rapid, primarily on the eucalyptus samples, which are suffering substantial degradation.
A Castillo, Y Cabrera, A F Preston, R Morris

Colonization of treated and untreated ponderosa pine exposed in Hilo, Hawaii
1995 - IRG/WP 95-20068
The rate of decay in above ground exposures is largely controlled by rainfall and temperature, factors which can be used to construct a climate index of decay hazard in above ground exposures. Developers of new biocide formulations have utilized this knowledge by establishing test sites in sub-tropical regions such as the Gulf Coast of the United States. More recently, field sites have been located in regions with even higher climate indices with more severe risks of decay. One such site is Hilo, Hawaii which receives nearly 4000 mm of rainfall per year and has near optimal temperatures for microbial growth. Previous field trials have shown that untreated control L-joints fail in as little as one year at such sites, but the organisms associated with these failures and their interactions in the deterioration process remain poorly understood. It has been suggested that results from such tests may be poor indicators of chemical performance under less severe exposures. To address this issue, the fungal flora colonizing wood was assessed in L-joints and deck boards exposed above ground in Hilo, Hawaii. The samples were either untreated or treated with 0.5% triazole 1, 0.5% tributyltinoxide, 0.5% 3-iodo-2-propynyl butylcarbamate, or 0.25% triazole 2 in mineral spirits or water. Selected samples were removed periodically and cultured for the presence of decay fungi. While basidiomycetes were not prevalent among the initial colonizers, they became increasingly abundant after 18 months of exposure. Among the fungi isolated were Trametes versicolor, Fomitopsis meliae, Schizophyllum commune, and Antrodia sinuosa. These fungi are also found under more temperate exposures suggesting that data from tropical sites represents a similar, albeit more accelerated, progression of decay organisms. Further studies on the decay capabilities of selected isolates are underway.
C M Freitag, J J Morrell, K J Archer

Biodetioration and strength reductions in preservative treated aspen waferboard
1983 - IRG/WP 2195
Experimental aspen waferboards, bonded with liquid or powdered phenol formaldehyde resins and treated by various methods with a wide selection of preservatives, were tested for fungal resistance in accelerated laboratory trials. Mold growth on the surface as well as weight and strength losses due to the actions of decay fungi were determined. Testing of board strength after decay in high and moderate-hazard exposure conditions required modification of decay tests used for solid wood. A range of protection was noted with no preservative system exceeding the efficacy of the inorganic salt formulations. Averaged over all treatments, strength loss and weight loss are well correlated. Field exposures of effective treatments are underway.
E L Schmidt, H J Hall, R O Gertjejansen, R C De Groot

Inorganic preservative levels in soil under treated wood decks after 8 years natural exposure in Borås, Sweden
2005 - IRG/WP 05-50233
Inorganic preservative components (Cu, Cr and As) were measured to a depth of 150 mm under deck structures made with Scots pine lumber treated with several different wood preservatives and installed in Borås Sweden 8 years ago. Higher contaminant levels were observed mainly under the drip lines and in the top 50 mm of soil. Under CCA treated decks, soil arsenic concentrations increased from background levels of about 3.5 mg/kg to 6-15 mg/kg in this zone. Copper and chromium levels were only slightly elevated above backgrounds of about 10 mg/kg and 3 mg/kg respectively. Copper levels were also only slightly elevated under decks treated with Tanalith E, Impralit KDS and Wolmanit CX-S. The Wolmanit CX-8 treated wood had concentrations averaging about 45 mg/kg in the top soil layer under the drip line while the Kemwood ACQ treated deck had concentrations above 100 mg/g in this zone.
P A Cooper, Y T Ung, M-L Edlund, J Jermer

Surface checking of CCA-treated radiata pine decking timber exposed to natural weathering
2000 - IRG/WP 00-40165
A field trial was established at four locations in Australia to assess the effect of CCA and CCA-wax treatment on the checking (cracking) of radiata pine decking timber exposed to natural weathering. Untreated decking timber and timber that had been pressure treated with water acted as controls. After 1 year's exposure the number and sizes of checks occurring in treated timber and controls were assessed. Timber treated with CCA-wax had fewer checks, which were significantly smaller in size than those in CCA treated timber and the untreated controls (except for check length in untreated timber). Checking in CCA treated decking timber resembled that occurring in water treated controls in that checks tended to be larger (longer and wider) and fewer in number than those found in untreated (exposed) boards. This finding tends to suggest that the pressure treatment process may have influenced the susceptibility of wood to check during exterior exposure. The difference in check number and size between CCA treated and untreated controls was, however, statistically insignificant. The effect of the different treatments on checking was consistent across the four exposure sites. The implications of these findings for the development of preservative formulations that reduce the checking of wood during exterior exposure are discussed.
P D Evans, P J Beutel, C F Donnelly, R B Cunningham

Impact of leachates from CCA- and copper azole-treated pine decking on soil-dwelling invertebrates
2002 - IRG/WP 02-50183
This study assessed the short-term effects on non-target soil invertebrates of leachates from a naturally durable hardwood and timber treated with two copper-based wood preservatives. Natural rainwater leachates from kwila decking, and radiata pine-decking treated with CCA or copper-azole, were collected and applied on mown lawn soil in Brisbane, Queensland. The soil study consisted of 5 treatments: an independent control (replicates untreated), wet control (replicates treated with rainwater only), CCA, copper azole and kwila-extractive leachates. Two applications of each treatment were made. Soil samples were collected before application and then twice after the first application (3 and12 days) and 3 times after the second (3, 8 and 12 days). Soil arthropods were extracted from soil cores using Tullgren funnels. Frequency analysis and multivariate techniques were used to analyse the data for treatment effects. Soil invertebrates were dominated by mites (84%), which were identified to family level. We did not detect any difference in the density of mites except in the kwila-extractive leachate, where mite density increased significantly. However, there were detectable differences in mite community structure between all treatments, indicating differential effects of the treatments on the soil arthropod community.
N Crumière, A House, M J Kennedy

Preliminary observations of the effect of growth ring orientation on the surface checking of flat sawn Southern pine decking
2005 - IRG/WP 05-20313
Checking in decking timber is a serious defect and methods of reducing its severity are required to ensure that wood can compete with alternative decking materials. The first aim of this research was to test the hypothesis that flat sawn Southern pine decking boards with growth rings oriented concave to the exposed surface will develop less severe checking when exposed outdoors than similarly exposed boards whose growth rings are oriented convex to the surface. A second aim was to examine the effects of wood type and three different types of fasteners on checking of boards. Five small decks were constructed each containing Southern pine decking boards with different growth ring orientations and manufactured from wood cut from close to the bark or nearer the centre of logs. Each decking board was fixed to the underlying sub-frame using 3 different types of fasteners, two of which were designed to permit flexural movement of the boards. The decks were exposed outdoors and after 6 months exposure the number and sizes of checks in the boards were assessed. Checks were significantly fewer in number and smaller in boards whose growth ring orientation was concave to the exposed upper surface than in boards whose growth rings were convex to the surface. There was no significant effect of wood type (inner or outer wood) and fastener type on the checking of boards. Orientation of flat sawn boards with growth rings concave to the exposed surface is a simple method of reducing checking of Southern pine decking boards. Further research is required to confirm these preliminary findings using preservative treated timber decking boards exposed for longer periods of time.
K Urban, P D Evans

Leaching of Copper from ACQ treated wood exposed above ground
2004 - IRG/WP 04-50219
The leaching of chemicals of ACQ Type C treated wood exposed above ground for 16 months was studied. Commercially treated Hem-fir boards (Tsuga heterophylla Raf. and Amabilis fir Forb) of 37.5 mm by 87.5 mm were used. The amounts of chemical leached monthly by the rainfall were determined and the leachate was collected and analyzed. Also, the environmental factors influencing the leaching were studied. The results showed that the first four months of exposure caused the greatest loss of copper (ranged 296.12 mg/m² - 593.37 mg/m²). From the fifth month onwards, the amount of copper leached begins to decrease. After 16 month of exposure, the percentage of copper leached was 3.95% from the weight uptake and 4.96% from the volume treated. The environmental factors influencing the leaching were time of exposure, volume of leachate collected, sun hours and temperature.
P A Chung, J N R Ruddick

Relating CCA fixation to leaching of CCA components from treated products
1995 - IRG/WP 95-50045
The relationship between chromium fixation in CCA-C treated wood, as determined by CrVI analysis of solution expressed from treated wood and the leaching of Cu, Cr, As and CrVI in a simulated rain test are evaluated for dimension lumber (2"x6") and pole sections. Leachate concentrations after 2 hour exposure to a misting spray (about 300 mm cumulative rainfall) decrease rapidly with increased degree of fixation. For jack pine lumber, the concentration of contaminants in the leachate approaches the levels found in completely fixed material long before the chromium fixation is complete. Copper and arsenic levels in the leachate reach relatively low values at chromium fixation levels of 90% and higher and chromium levels at 95% and higher fixation levels. For red pine pole sections, the trend was similar except that higher levels of chromium fixation were required to minimize leaching rates. The results confirm that fixation procedures such as the chromotropic acid and other CrVI detection methods are conservative and following them guarantees that leaching losses are minimal.
P A Cooper, R MacVicar, Y T Ung

Preliminary Observations of the Effect of Kerfing on the Surface Checking and Warping of Flat Sawn Southern Pine Decking
2007 - IRG/WP 07-20360
Checking and warping of decking timber are serious defects and methods of reducing their severity are required to ensure that wooden decking can compete with alternative decking materials. Kerfing is effective at reducing the checking and distortion of square cross-section lumber, and the checking of roundwood. In the past it has also been applied to preservative treated decking boards, however, there is no information on whether kerfing reduces the surface checking or warping of treated boards. In this study one, two or three kerfs were sawn to depths of 10, 13, or 20 mm into the underside of 140 mm (width) x 40 mm (thick) southern pine decking boards. Kerfed boards and matched unkerfed controls were exposed to natural weathering for 1 year and the surface checking and distortion of boards was measured. The aim was to determine whether sub-surface kerfing of decking boards could reduce the surface checking and distortion of boards, and the kerfing treatment (kerf number by depth) that was most effective at reducing both the checking and distortion of boards. Kerfing reduced the cupping of boards exposed to the weather, but had no significant effect on twist, or bow. Both the single and triple kerfs were effective at reducing the cupping, whereas the double kerfs were ineffective. There was a positive correlation between kerf depth and reduction in cupping, and the kerf sawn to a depth of 20 mm was particularly effective at reducing cupping. Kerfing had no statistically significant effect (p>0.05) on the surface checking of boards, although in most cases checking of boards containing kerfs was greater than that occurring in the unkerfed controls. Further research is needed to confirm these preliminary findings.
R Ratu, J Weizenegger, P Evans

Development of a Weatherometer to Accelerate the Surface Checking of Wood
2008 - IRG/WP 08-20388
There is significant interest in developing preservatives that are better at preventing wood from checking. Currently, however, there is no accepted test methodology for accelerating the development of checks in wood samples so information on the effectiveness of treatments at restricting checking can be obtained more quickly. This paper describes the development of a new type of weatherometer (Accelerated Check Tester) and associated weathering cycles to accelerate the surface checking of wood. The device permits the testing of realistic-sized decking board samples that are oriented horizontally and restrained by fixings. It uses computer-controlled water spray and infra-red heating systems to expose samples over a 5 day period to wetting and drying cycles. Desiccated air is also blown across the surface of samples to further increase the effectiveness of the drying cycle. The Accelerated Check Tester operated continuously and trouble-free for 24 weeks during an experiment, which examined the effect of different weathering cycles on the checking of southern pine and western red cedar decking samples. Samples exposed in the Accelerated Check Tester developed large numbers of checks, some of which were quite big, particularly those in southern pine samples. Weathering cycles that increased the severity of drying by increasing drying time or temperature did not significantly increase checking. Similarly, the inclusion of a freezing step in the weathering cycle had little effect on checking. In contrast, samples subjected to a cycle that included exposure to ultraviolet light developed significantly more and larger checks than samples subjected to any of the other cycles. Checking was much more pronounced in southern pine samples than in western red cedar samples. The Accelerated Check Tester should be a very useful tool for obtaining information on factors that affect the checking of wood. Furthermore, it could also allow companies developing wood preservatives and associated water repellent additives to rapidly obtain information on the ability of treatments to restrict checking and so shorten the development time for new wood protection systems.
R Ratu, P D Evans

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