Three Gram negative bacteria isolated from brownstained western hemlock were investigated for their capacity to produce hemlock brownstain. Brownstain was observed when infecting western hemlock with two bacteria. Oxygen was strongly indicated as being indespensable for the development of brownstain in infected samples. However, pH did not seem to influence the production of this stain.
Oriented strandboard (OSB) manufacturing technology has been advancing steadily during the past few years. Today, the industry can produce higher quality OSB at lower costs than ever before in the product's history. Research results have shown that drying costs can be reduced and strand quality can be improved through proper wood yard management, and that the production efficiency can be improved through various ways of optimizing the pressing and processing operations. OSB quality has been improved and board density has been reduced by using long and thin strands in panel face layers and relatively short and thick strands in the panel core. The press times have been reduced by using higher press temperatures and higher mat face-layer moisture contents. The degree of strand alignment has been improved by controlling the falling distance from the alignment heads to the top of mat being formed. Strands alignment has been further enhanced by arranging the alignment disc gaps in such a way so that narrower strands can be aligned through narrower gaps and directed towards core while wider strands can be aligned through wider gaps and directed towards the panel surfaces. Based on these technical advancements, OSB can be produced faster and at a lower density without sacrificing quality. Consequently, the OSB industry is in the position to improve panel quality without resorting to costly options such as increasing resin content and press time.
L'alignement précis des équipements de coupe est un moyen recommandé pour assurer la maximisation du rendement matière et de la qualité des produits manufacturés. Les tendances de l'industrie s'orientent de plus en plus vers l'utilisation de scies minces et vers une réduction maximale des dimensions-cibles. Il est essentiel pour la qualité des produits désirés que les préposés de l'entretien et de l'alignement des machines fassent un ajustement de haute précision. Le succès d'un alignement précis dépend en grande partie de la précision des outils utilisés pour accomplir ce travail. Un niveau de précision est calibré de façon telle à permettre de mesurer les déviations du nivelage par unité de millième de pouce. Ce livre propose des formules pratiques que l'expérience en milieu de travail peut mettre à profit. Les méthodes d'alignement s'appliquent à l'ensemble de la machinerie des centres de transformation: équarrisseuse-déchiqueteuse ("Chipper Canter"), scie de tête à ruban avec le chariot, scie de tête à rubans jumelés ("Twin Band"), refendeuse verticale, refendeuse à ruban horizontal, scie de tête circulaire avec le chariot et déligneuse à scies multiples ("Bull Edger").
As a result of its potential as an added-value, environmentally acceptable, high performance wood product, borate-treated lumber has attracted the interest of the Canadian forest products industry (Byrne 1990). One of the potential markets for borate-treated wood in Europe and North America is millwork. Currently millwork manufacturers use light organic solvent preservatives to provide durability to their products but there are a number of reasons why this situation may change in the near future. There are increasing pressures on uncontrolled emission of volatile organic solvents from treated wood and public concerns regarding some of the active ingredients now in use (Orsler and Holland 1993). The use of borate-treated wood eliminates both of these problems and may provide some additional advantages by eliminating batch processing in the manufacture of joinery. The one factor which is likely to have the greatest impact on the performance of borate-treated millwork is the mobility of the boron. Borate-treated wood is currently approved for use in exterior exposure in New Zealand provided it has a three-coat paint finish. Nevertheless there is concern outside New Zealand that redistribution of boron within the treated wood could lead to localized depletion and decay. An L-joint test of borate-treated wood was set up by Forintek to determine whether preservative depletion and subsequent decay is likely to be a problem. This report describes the performance results of this trial after six years and compares borate content of the L-joints initially and after five years exposure.
Discolourations of hem-fir, usually called hemlock brownstain, have become an economically important problem with the move towards increased kiln-drying of the wood species mixture and added-value products in which discolourations cannot be tolerated. These discolourations, clearly different from sapstain, can occur in several types and intensities and are a serious problem in high-value markets. Because little is known about their causes means for their control are still unavailable. Therefore fundamental research was initiated to elucidate the biology and chemistry of hemlock brownstain and to suggest control measures. A post graduate student was hired to undertake laboratory and field work as part of a Ph.D. program. The thesis subject was "the role of microorganisms in the phenomenon of hemlock brownstain". The thesis covers: a literature review; laboratory work to locate the stain and define its nature; a storage study of logs and lumber to monitor progress in development of brownstain; fungal isolation work and sap characterization studies; in vitro production of hemlock brownstain in wood and sap; and additional laboratory experiments to determine what factors influence the formation of the brownstain. In addition to the thesis research the role of bacteria in the formation of the stain was investigated in the laboratory and the ability of various chemicals, including fumigants, to prevent the stain was tested in small-scale field test. This report provides an overview of the findings and provides recommendations for future work. The experiments clearly demonstrated that a non-specific microflora can produce brownstain which led to the hypothesis that microorganisms could be involved in hemlock brownstain. Based on our knowledge of the coastal sawmilling industry a strategy of minimizing fungal infection and rapid handling of the tree breakdown into final wood products could probably be the best approach to help reduce the problem. In terms of future work we recommend that work to understand the mechanism of DDAC in mitigation of the browning take precedence in future work on hemlock brownstain.
This report compares international standards for particleboard, waferboard, OSB, MDF, hardboard as well as cement bonded wood composite panels. Property requirements are discussed and comparisons are made between countries. Formaldehyde emission regulations were surveyed in eighteen countries.
This report evaluates a new fluctuating pressure treating process, with a small pressure variation, that could be easily implemented into a treating plant with a control value. Coastal western hemlock being a relatively difficult species to impregnate was chosen as a suitable test species. Incised and unincised hemlock was used to relate to present industry practices.