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7.4 Deficiencies in the quality of timber This submodule contains: • • •
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concepts (introduction and theory of the deficiencies in the quality of timber) explanation of concepts (description of particular wood defects) (however in other submodules it can contain also Instructions etc – how it suits particular theme) examples (photos and drawings of particular defects of timber – in this case) (in other modules it can contain description and use of tools, methods etc – how it suits particular theme) activity - online exercise http://toolsforskills.eu/drymos/ (other modules can contain further reading, links, FAQs, …)
CONCEPTS (Submodule 7.4 Deficiencies in the quality of timber) The quality of timber is undoubtedly the main criterion to decide how to use timber as well as particular financial evaluation of timber. One of the basic indicators of the quality of wood is the number of defects and their size (scope). Ability to recognize defects and assess its potential impact on woodworking (further processing of timber) is therefore necessary for any working with wood. Knowledge of the issues is crucial for anyone who is engaged in wood processing as well as buying or selling timber. The term "defect" is artificial, created by man purposefully. In nature there are no defects. Term was introduced, in order to express the suitability or unsuitability of the material for the required application, and assign it to the corresponding price. Thus can easily happen that what is in one wood industry considered as a defect, it may be for another purpose use welcome priority. The aim of this of material is to improve and deepen the knowledge about timber defects for owners, forest managers, forest land managers for optimizing the yield of wood assortments to reach competitiveness in the domestic and international timber markets. The aim of this submodule is to provide rich visual material which tries to capture the variability of defects.
Classification of characters for qualitative assortment of round-wood timber With regard to the practical qualitative assortment of round-wood timber, the timber characteristics (defects) are divided into two groups: A/ growth characters incurred during tree growth or incurred as an impact of abiotic and biotic factors in its lifetime, B/ characters mainly caused by logging and storage as a result of breaching technological procedures and/ or extending time of wood supply.
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Terms and definitions for each defect according EN 844-2 to 12. A/ growth characters
width of annual ring
sweep spiral grain taper eccentric pith double pith ovality reaction wood compression wood
knot
epicormic back eye resin pocket tumor cancer rose furrow curly grain bulge nodule barber chair scar T recess foreign body bark pocket buttress shake, crack
B/ characters mainly caused by activities in logging and storage check crack end shake starry Splits (checks) not passing passing penetrating by production
one directional more directional
shear
compression wood tension wood
blue stain
standard knot covered knot partly covered knot uncovered knot loose knot unsound knot blind knot group knots
undercut (notch) tapping cut dote brown coloration - streakiness mould fungal decay
insect attack
shallow attack deep attack
ring shake heart shake frost crack caused by lightning 3
Decay
false-heart brown heart (Quercus) wet heart (Abies) black heart (Fraxinus)
hard rot soft rot white rot brown rot sapwood rot heart rot
EXPLANATION OF CONCEPTS (Submodule 7.4 Deficiencies in the quality of timber) Characterization and measurement of growth characters Width of annual ring The annual ring is equivalent to one year's growth timber of growth period of tree. It is measured in millimeters, both part of the growth ring, i.e. lighter spring wood usually darker and denser summer wood. Sweep It is a deviation from the longitudinal axis of round timber. Unidirectional sweep is characterized by only one bend, multidirectional is characterized two or more bends in one or more planes.
Measurement of unidirectional sweep
Measurement of multidirectional sweep
It is expressed in centimeters per meter. The most common measurement of surface round timber. It is calculated as the ratio between height of the curve at the point of greatest sweep, in centimeters and the distance between the extremities of the bend, in meters to one decimal place.
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In multidirectional sweep is theoretically divided into imaginary cuts of several parts, either straight or with unidirectional sweep. Then they measured individually. Individual sweep is expressed in centimeters per 1 meter of length and shall be recorded separately.
Spiral grain It is a spiral course of fibers around marrow. It is expressed in centimeters per meter. It is measured determining the distance in centimeters (to the nearest centimeter) per meter length of towards growth fiber and line parallel to the axis of the cavity in the whole length.
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Taper The gradual reduction of the thickness of stem is depending on the height of the timber or is depending on the length of logs. The thickness is measured at each end of timber at least 5 cm from each end (in case butt log is measured at 1 m from the bottom forehead). Taper is expressed in centimeters for 1 m of length as the difference thicknesses between points of measurement. If the point (s) of measuring is significant irregularity of growth than it is measured at a distance of 5 cm from these place.
Eccentric pith The Marrow, which is located at a significant distance from the geometric center of the cross section logs. Is measured distance of pith from the geometric center of the lower end or the thinner end. It is expressed in centimeters or percentage of the thickness of the corresponding end. 6
Ovality It’s a shape of the cross-sectional area with a significant difference between the larger and smaller diameter. It measures the maximum and minimum cross-sectional thickness of at least one meter from the bottom of the lower end. It is expressed in centimeters or as a percentage of maximum thickness in percent.
Double pith The most commonly accrete of two thin stem during tree growth. Both pith of growth rings form an irregular course. The occurrence of this character is recorded without measurement.
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Reaction wood Wood with different anatomical characteristics, forming mainly on inclined or bent parts of the stems and branches when the tree is trying to return from an inclined position to the initial position. Tension wood is reaction wood that forms on top of branches and inclined or bent trunks of deciduous trees. Compression wood is wood that forms on the bottom of the branches and the inclined or bent trunks of coniferous trees. The occurrence of this character is recorded without measurement.
Compression wood Manifests itself as a reddish-brown coloration condensed structure of the wood going along the annual rings. The occurrence of this character is recorded without measurement.
Knot Knot is part of overgrown branches into wood which is the most frequent and an important quality feature of wood. 8
Standard knot It bulges without signs of rot.
Covered knot It is a knot which is accreting on the sectional area of at least three-quarters of its circumference with the surrounding wood. Partly covered knot Is the knot which is the accreting on the sectional area more than one quarter and less than three-quarters of its circumference with the surrounding wood.
Uncovered knot Is the knot which sees at the round surface of timber. Loose knot Is the knot, which is not strongly fixed with surrounding timber.
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Unsound knot The knot is damaged by rot.
Not blind knot It is a knot which is accreting on the sectional area of at least quarters of its circumference with the surrounding wood. Blind knot Is the knot which not sees at the round surface of timber.
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Group knots Knots are placed so that between adjacent knots is not the normal continuance of fibers. It conforms as the distance between two successive knots is less than the width of the timber, or less than 150 mm, if the width of the timber exceeds 150 mm.
Epicormic Is the bough or its part that is visible at the round surface of timber. Generally is formed when there is a sudden illumination of part stem. Measurement of knots that are visible at the round surface of timber is measured in millimeters as the smallest diameter knots.
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Back eye Is the black knot in size up to 5 mm. The occurrence of this character is eye recorded and is measured in millimeters.
Resin pocket Coniferous species - lenticular cavity in wood which contains or contained resin. Broadleaves can have resin pockets like cavity in growth rings filled by gummy material.
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Tumor Larger lignified nodule with wavy fibers that create characteristic texture of wood. Measured the length of the nodule at the round surface of timber in meters to two decimal places or as a percentage of the length of the cut or tree-length log.
Cancer Is the accrual on the surface of logs or cavity which was formed by the strong growth of fungi or microscopic fungi on the surface of living tree. Measurement is performed as the measurement of the tumor.
Rose Is concentrated corrugation of bark which indicating the internal character usually knot. The occurrence of this character is recorded without measurement.
Furrow Is expressed as longitudinal corrugation or depressions on the surface of logs in generally darker. The occurrence of this character is recorded without measurement.
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Curly grain Create fibers with fixed irregular curvature. The occurrence of this character is recorded by measuring the surface of the logs in meters to two decimal places, or as a percentage of the length of the cut.
Bulge Create local bulge on the round surface of timber which generally indicates the presence of covered knots. It measures the amount of bulge (corrugation) in millimeters above the rounded surface of the cut-out. It can also measure the length.
Nodule It lug around a group of epicormics, dormant buds or branches. The occurrence of this character is recorded without measurement. Barber chair Is a character on the round surface of broadleaf round timber with thin crust (usually beech) oval-shaped curve indicating internal character – covered knot. The occurrence of this character is measured as the height of the arc of implied oval base in millimeters and the incidence of recorded character.
Scar Surface lesion completely or partially overgrown. The occurrence of a character is recorded without measurement.
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T reces The longitudinal scar incurred in a tree during growth which is at the end of round timber and appear in the shape as letter T. The occurrence of a character is recorded without measurement. Foreign body Occurrences of bodies with different origin in timber (metal splinters, nails, wires, ropes, rocks, etc.). Detecting visually or with the detector. Bark pocket Is occurring in whole or in part ingrown bark. Full overgrow is visible only to the crosssection round timber. Partial overgrow is visible as a furrow on round surface of the log. Overgrow is measured as a length in meters to two decimal places.
Buttress It protruding ribbed thickening at the bottom of the stem. It measures the difference cant buttress roots above the ideal cylinder head recess in millimeters.
Shake, crack Is cracking by splitting timber along the fibers. Crack by fragmenting wood is a major feature influencing the technical use of wood. 15
Ring shake It is a circular crack that passes year-on rings, directed deep to log and causes serious and significant reduction in the quality and technical use of wood.
Heart shake It radial crack at the forefront based of pith. Crack length is measured from the direction marrow the circumference of log in millimeters. Can be expressed as a proportion of the thickness of the cut as a percentage.
Frost crack Is larger radial crack length caused by frost in the growing tree, which takes place longitudinally from the sapwood towards the pith. Crack length measured in inches, or as a proportion of the length of cut-outs as a percentage.
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Caused by lightning Arises by flash. Its burst longitudinal fibers directed towards the sapwood the pith. It is measured as frost cracks.
Decay It is timber decay by fungi or other microorganisms which causes a decrease in the hardness of the gradual loss of substance and strength and often leads to a change in texture and color. Hard rot The initial stages of decay, characterized by stripes or spots changed color and general texture and strength properties of timber are still largely changed little.
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Soft rot Is caused by rot of fungi or micro-organisms which attack cellulose and hemicellulose and significantly impair the strength properties of timber - often arises on wood which is in contact with soil or water. Strength properties of timber are changed.
White rot It is rot caused by fungi in an advanced stage which break down cellulose, hemicellulose and lignin usually accompanied by a light-colored timber.
Brown rot It is rot caused by fungi that break down cellulose and hemicellulose, leaving brown crumbly remains unaffected lignin - is characterized by dark cracks along and across the fibers. Sapwood rot Rot is occurring in the sapwood.
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Heart rot Rot is occurring in the heartwood.
False-heart Unhealthy red or brown colored false sharply defined heart in the shape of circles, flame or a starfish on the foreheads (ends) in generally beech logs.
Brown heart (Quercus) Flame form at an early phase of decay is expressed by changing the colors of the heart timber to brown.
Wet heart (Abies) Is a change of the natural color of timber that will not change any of its technical characteristics. Black heart (Fraxinus)
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Abnormal dark brown to black coloration of heartwood of ash. It may not be indicative of decay and does not change in technical properties of timber. Rot of heart is measured as the smallest area affected by decay, expressed in centimeters or as a proportion of the surface of end log. Sapwood rot is measured from the circumference of the log towards the marrow in centimeters or as a proportion of the surface of end log. Upon the occurrence of rot on an oval contaminated log is measure the length of the log in centimeters.
Characters mainly caused by activities in logging and storage Split (check) Incorrect use of harvesting and storage technology of the timber and infringement of deadlines production and supply of wood are resulting of cracks which have the effect of reducing the quality of timber.
Check It is short, narrow and shallow crack.
Crack Is the crack which is occurring on the round area of stem and can go up to the end shake. End shake Is the crack on the end of log.
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Starry It is grouping two or more of heart shakes
Not passing check It is occurs on the end of log and not passing to its oval side. Passing check It is occurs on the end of log and passing to side of the log.
Penetrating check It is occurs on the end of log and passing to both sides of the log.
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Production check It is an ongoing longitudinal check at the butt of round wood which is caused by breach of right technology of cutting trees. The length of check is measured from pith towards the end of the log in millimeters. Production check is often resulted in a significant change of classification to lower quality timber.
Shear It is cause holes in the end of log after torn fibers. It was caused by inappropriate management of the main cut, failure to observe a key or fall tree in the deflected direction.
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Undercut It is visible as a chock at the lower end. Undercut was created to determine the fall tree and unless it is very deep and does not constitute proper directional cutting, devalues butt cut, it cause a loss of mass.
Tapping cut Stripped bark in lower part of the stem of coniferous species with notches for obtaining resin. Has the effect of reducing the quality of butt of round wood. Dote
The initial phase of decay characterized by stripes or spots changed color, firmness and texture of the timber are still unchanged - it occurs after cutting of improper or prolonged storage.
Brown coloration – streakiness The color changed as flame brown spot occurring after cutting.
Mould Is a fungal growth with corrugated or silty appearance that occurs on the surface of the logged timber and stored in a humid environment. 23
Blue stain The color changed from light blue to black due to mushrooms - usually occurs in sapwood of specific trees of improper storage and shipment of wood extending in growing period and humid weather.
Fungal decay Is occurrence of sporophore of fungal decay caused by long-term incorrect storage of timber. Incest attack Shallow attack Is insect attack to a depth of 3 mm with pronounced feed mark of corridor in the structure of the wood.
Deep attack Is insect attack to a deeper than 3 mm with feed mark of corridor in the structure of the wood.
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Mechanical damage of timber Is occurs in damaged parts of butt. It cause skidding, abrasion of bark and surface parts of the wood structure.
EXAMPLES – included in the explanation of concepts as pictures and drawings (Submodule 7.4 Deficiencies in the quality of timber)
ACTIVITIES, FURTHER READING, LINKS, FAQs (Submodule 7.4 Deficiencies in the quality of timber) http://toolsforskills.eu/drymos/
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