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 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.
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.
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.
In some western hemlock lumber pieces “brownstain” develops as the wood dries. Brownstain is deleterious to high-value appearance-grade stock because it reduces shop and better grades of hemlock to paint grade. The stain varies in color and can be superficial or subsurface. The incidence of subsurface brownstain, usually as a striped discoloration termed “zebra” stain has been seen more frequently with the increased kiln drying of western hemlock. When brownstain is subsurface, planing allowances have to be larger than desired, resulting in wasted fibre. A 1995 Forintek research project indicated that water storage of logs resulted in more surface brownstain during air drying than dryland storage but the numbers of logs were insufficient to determine if there was a significant difference. The project reported here was set up to investigate further whether storage influenced the development of brownstain and whether it occurred during kiln drying.
Three hundred cubic metres of hemlock logs were freshly cut, 60 m3 sent to a sawmill for conversion and the rest split between dryland and water storage. After two, four six and eight the stored logs were sawn in batches of 60 m3 into 100mm squares. These were examined individually before and after kiln drying and potential and observed brownstain marked of the faces. The squares were then planed and the extent of subsurface brownstain assessed.
Wet areas were apparent in both sapwood and heartwood of freshly sawn hemlock squares but were not useful in predicting the site of potential brownstain. Kiln drying gave the wood a toasted appearance in some of the drying runs which was removed by even the lightest planing. The most predominant form of brownstain was subsurface zebra (striped) stain which developed only during drying. Before planing, the presence of zebra stain was usually detectable as a shadow at the surface of dried lumber. This stain was up to 3 mm beneath the surface and therefore up to 3 mm had to be removed by planing to reach non-discolored wood. Zebra stain occurred only in the sapwood, usually the inner sapwood alongside the heartwood. The stain follows this zone along the boards. The zebra stain was more likely to be visible on edge-grain than on flat-grain, possibly reflecting moisture movement out of the boards. Some logs showed more zebra stain than others and appear to be predisposed to the stain. Both water and land stored logs, for short and longer terms, developed brown stain. Grey stain was also present but less common, and appears to be part of the natural character of hemlock wood. In general the longer the log storage time, up to 8 months, the less brownstain resulted, but based on the current information, changes in log storage type specifically to reduce development of brownstain are not justifiable.
In this work the lumber with the drier surfaces, which developed the least brownstain, was from the material that had been stored longest and included both water and dryland stored logs. There is an indication of interaction between log drying, storage time, air and kiln drying of lumber and the development of surface or sub-surface brownstain. Further investigation of these interactions may help to devise methods of reducing the incidence of hemlock brownstain.
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.
