Wood defects- these are deviations from the norm in the structure of the trunk, all violations of the physical condition. Defects include: knots, cracks, defects in the shape of the trunk, wood structure, chemical stains, fungal infections, biological and mechanical damage, processing defects and warping.

The most common defect is bitches– the bases of the branches that are present in the wood of the trunk. When cutting wood, knots appear on its surface different forms and types. Based on the shape of the cut on the surface of the wood, you can see round, oval and oblong knots, and according to the degree of fusion with the wood, they are further divided into fused, partially fused and unfused, or falling out. When cutting wood into boards, knots may have different position – seam, edge, rib, stitching– in the case of a longitudinal section of a knot, part of it extends simultaneously onto two edges of the same side of the board and end– when the knot ends up at the end of the board. According to the relative position of knots on lumber, they are divided into scattered– single or separated from each other at a considerable distance, group and branched.

According to condition The wood of the body of the knot itself is divided into: light healthy, dark healthy, healthy with cracks, rotten, rotten and “tobacco”, in which the rotten wood is completely or partially replaced by a loose mass of rusty-brown or whitish color. The presence of knots in wood leads to a decrease in strength, complicates its processing and gluing, and reduces quality (especially when their number and diameter are large). Unfused and rotten knots significantly reduce the quality of wood, and in some cases they make the wood unsuitable for making products (for example, boards).

Another type of wood defect is cracks, formed when wood breaks along the grain. Cracks occur in growing and felled trees. The first ones include metic, peeling and frost cracks, the second ones include shrinkage cracks.

Methic cracks have the greatest extent, which pass through the core of the tree trunk, and when the harvested wood dries, their size increases. In round pieces of wood, such cracks usually occur at the ends; in lumber or parts - at the ends and side surfaces.

When wood delaminates along the annual layer, peeling cracks form, usually at the border of a sharp transition from interlayer wood to large-layer wood, and are found in trees of all species. During drying of wood, the peeling crack increases.

When drying wood under the influence of internal stresses, shrinkage cracks. This type of cracks differs from others (metic and frost-breaking) in their shorter length and depth.

In boards, cracks can extend to the face, edge or end. Accordingly, they are called face, edge and end. Cracks, especially through ones, disrupt the integrity of the wood material and reduce its mechanical strength.

2. Defects in the shape of the trunk

The processing of wood of all species is often complicated by the following defects in the shape of the trunk: camber, ovality, growths, curvature and rumpiness.

Convergence expressed as a decrease in log diameter or width unedged boards, exceeding the normal run, which is equal to 1 cm per 1 m of assortment length. As a rule, it is greater in deciduous trees, especially in trees that have grown in open spaces, and along the length of the trunk - in the apical part. This type of trunk shape defect increases the amount of waste when sawing and peeling round timber and causes the appearance of radial inclination of fibers in the veneer. Ovality the trunk is an ellipsoidal cross-section of the end, at which larger diameter 1.5 or more times higher than the smaller one.

Wood processing is complicated by growths in the form of local thickening of the trunk various forms and sizes. Growths are formed as a result of tissue growth under the influence of various irritants - fungi, low or high temperatures, etc., as well as fires, mechanical damage and other reasons.

Rice. 2. Growths: a) smooth, b) lumpy

Smooth growths (Fig. 2a) often appear on pine and birch trunks. The annual layers in places of growths are usually wider than in the trunk. Lumpy growths, or burls (Fig. 2b), are formed mainly on the trunks of birch, walnut, as well as maple, black alder, ash, beech, poplar, etc. The wood in the burl zone has an irregular structure with a curled-wavy direction of the fibers and with dark-colored inclusions in the form of small spots, dashes and dots. When cut, mouthguards have a beautiful texture, so they are used as a material for artistic crafts and production of sliced ​​veneer.

Such a trunk defect as his curvature, also makes it difficult to use round timber and increases the amount of waste during sawing. The curvature of the trunk is the deviation of the longitudinal axis from a straight line, and it can be with one bend or complex - with two or more bends.

This type of trunk defect often occurs, such as stubbornness, which is expressed in a sharp increase in the diameter of the butt part of round timber, i.e. when the diameter of the butt end is 1.2 times greater than the diameter at a distance of a meter from this end. When sawing and peeling wood, the presence of such a defect leads to an increase in the amount of waste and, in addition, causes the appearance of a radial inclination of fibers in the veneer. The hardness of the round timber also makes it difficult to use round timber for its intended purpose and complicates wood processing.

3. Defects in the structure of wood

When processing wood, defects in the structure of wood often occur due to the incorrect structure of the trunk. The following types are distinguished: structural defects of wood:

1) cross-layered, or fiber inclination, which is the deviation of the fibers from the longitudinal axis of the trunk;

2) list– continuous or local in the form of a sharp thickening of the wood of the late annual layers;

3) curliness– sharply wavy or tangled arrangement of wood fibers (wood blanks with such a defect are used in the manufacture artistic products, furniture, axes and various crafts);

4) curl– local curvature of the annual layers near knots or shoots (wood with such a defect is used in furniture production and artistic crafts);

5) resin pockets. Found in wood coniferous species, especially in spruce, are cavities between the annual layers filled with resin;

6) tarred– a section of coniferous wood, richly impregnated with resin;

7) double core– two cores in one cross section of the log, which are formed at the bifurcation of the trunk;

8) stepson– stunted and dead second apex, which is usually located at an acute angle;

Rice. 3. Defects in the structure of wood: 1 – types of fiber inclination: a – tangential inclination in round timber; b – local; 2 – heel: a – solid; b – local; 3 – fibrous curling in birch; 4 – one-sided curl; 5 – pocket; 6 – double core in a pine trunk; 7 – stepson; 8 – dry side; 9 – pine cancer; 10 – germination: a – open; b – closed; 11 – false nucleus: a – rounded; b – star-shaped; c – lobed

9) dry side. Occurs as a result of damage to the bark of a growing tree in the form of a dead section of the trunk;

10) germination. It is an overgrown wound, usually filled with remnants of bark and dead tissue;

12) false core which resembles a real nucleus, but has a more heterogeneous structure and less correct form, stands out as a dark, unevenly colored zone in the central part of the trunk, separated from the sapwood by a dark and sometimes light stripe, appears from the action of fungi, severe frosts, as a reaction to wounds and for other reasons, while the wood of the false core is more fragile and less durable, and appearance, as a rule, worse;

13) internal sapwood– the presence of several annual layers in the heartwood, which are similar in color and properties to sapwood, and it has reduced resistance to decay and increased permeability to liquids;

14) watershed– wood defect in the form of areas with high humidity as a result of the action of bacteria, fungi, penetration of rainwater through wounds or from oversaturation of the soil with moisture.

4. Fungal infections

When cutting wood, in some cases, mushroom sound spots– abnormally colored areas of the kernel that are formed in growing trees under the influence of wood-staining or wood-destroying fungi. In felled wood, further development of this defect stops. Fungal core spots are observed on the ends in the form of spots of various sizes and shapes of brown, reddish-gray or gray-violet colors. This defect causes: a decrease in impact strength, an increase in water absorption and permeability, a deterioration in the biostability and appearance of wood; the strength under static load remains almost unchanged, and the structure of the affected wood is preserved.

When storing wood on damp sapwood, mold often appears - mycelium and the fruiting of mold fungi on the surface of the wood in the form of separate spots or a continuous coating, and the wood is stained in various colors. Mold does not affect the mechanical properties, but deteriorates the appearance of the wood; after drying, it is easily removed, leaving dirty and colored spots.

In felled wood there are often formed sapwood mushroom stains– abnormally colored areas of sapwood under the influence of wood-destroying fungi that do not cause the formation of rot. Sapwood mushroom stains do not affect the mechanical properties of wood, but worsen its appearance and increase water resistance. By color, blue is distinguished - in the form of a gray color of sapwood with bluish or greenish tints and colored sapwood spots - in the form of orange, yellow, pink and brown color of sapwood. Fungi that stain sapwood can destroy glue and paint coatings.

In felled wood during storage in the warm season as a result of the development of bio chemical processes with or without the participation of mushrooms, a defect occurs such as browning. Browning of wood manifests itself in the form of abnormally colored brown areas of hardwood various shades. Browning is observed on the ends in the form of spots of various sizes and shapes, and on the side surfaces - in the form of elongated spots, stripes or complete damage to the sapwood, while the appearance of the wood deteriorates and the strength and hardness are slightly reduced. To prevent browning of wood, lumber is steamed.

Great harm applied to wood rotten formed under the influence of fungi. Rot is distinguished by the color and structure of the lesion - variegated sieve, white fibrous; and also by type - sapwood, soundwood and external rotten.

Wood affected by rot is a source of fungal infection for various wooden structures. Rot

develops gradually and has three stages: in the first, only the color of the wood changes; on the second, the wood partially changes structure and hardness under the influence of rot; on the third, the wood completely loses its strength and hardness. Depending on the stage of development of the rot and the size of the lesion, the quality of the wood can significantly decrease.

5. Chemical stains, biological damage and warping

In the process of wood processing, a phenomenon such as chemical coloring of wood is often encountered - abnormally colored areas in cut wood that arise as a result of chemical and biochemical processes.

In most cases, it is associated with the oxidation of tannins. Typically, such areas are located in the surface layers of wood - at a depth of 1–5 mm.

As the practice of wood processing shows, chemical stains only change its color and shine, while the other properties of wood remain unchanged. With intense natural coloring, the appearance of the wood deteriorates, but as it dries, chemical coloring gradually fades.

If the technology for storing freshly cut timber is violated, the wood is subject to biological damage in the form of wormholes - passages and holes made in wood by insects and their larvae (beetles, butterflies, termites, etc.). Optimal conditions for the life of these insects – a temperature of +18–20 °C and a relative air humidity of 60–80%. Wormholes vary in penetration depth: superficial (no more than 3 mm deep), shallow (no more than 5 mm in round timber and no more than 5 mm in lumber) and deep. Moreover, they can be non-end-to-end and end-to-end, i.e. extending onto two opposite sides boards.

A superficial wormhole does not affect the mechanical properties of wood, but shallow and deep ones violate the integrity of the wood and reduce the mechanical properties.

At long-term storage with a violation of technology, a so-called rotting wormhole can form in wood, which is caused by house pests that can develop on dry wood - furniture and house grinders, house beetles, termites. In this case, the number of deep passages is large, and the wood inside them turns into a rotten mass with high content drill flour.

When drying or moistening, as well as during mechanical processing, as a result of anisotropy of shrinkage - swelling and internal stresses in wood - a phenomenon such as warping in the form of a change in the form of the assortment. Warping of lumber occurs different types: longitudinal along the surface, complex, longitudinal along the edge, transverse, and also like a wing (wing-likeness) (Fig. 4). The nature of the warping depends on how it was cut from the log. Warping reduces the quality of lumber and wood products, complicates processing and cutting, increases the amount of waste and generally makes it difficult to use wood.

Rice. 4. Types of warping: a – transverse across the face; b – longitudinal along the surface; c – wingedness

The phenomenon of warping is most often observed in lumber obtained by processing birch.

6. Foreign inclusions, mechanical damage and defects in machining

In a number of cases, during the processing of wood, foreign inclusions are found in the form of a foreign body of non-wood origin - nail, wire, metal shard or stone. An external sign of such a defect may be local swelling and folds of bark in the wood, a dent, or a hole. Such inclusions make it difficult machining wood and often cause damage to cutting tools - cutters, circular saws, cutters, etc.

Mechanical damage and defects in machining can be of different nature and different origins.

Sometimes you come across charred wood. Charring of wood is the result of damage by fire, changing its shape, making it difficult to use and causing loss of wood.

Carra– this is damage to the trunk during tapping, which causes tarring of the wood.

Obzol is a part of the side surface of a log that has been preserved on edged board or parts, which reduces the actual width of the board and makes it difficult to use.

When processing wood with a cutting tool, risks on its surface, waviness– non-flat cut or irregularities in the form of arc-shaped elevations and depressions as a result of cylindrical milling of wood.

Poor-quality wood processing leads to the appearance of surface hairiness in the form of the presence of incompletely separated fibers and mossiness - the presence of tufts of incompletely separated fibers and small wood particles. Zarub– local damage to the wood surface with an ax. Gash– local damage to the wood surface with a cutting tool (saw). When harvesting and processing timber, problems arise flakes– lateral cracks extending from the end of the round timber. In similar work, it often turns out breakouts– recesses with uneven surfaces as a result of local removal of wood under the influence of tools or machinery. When processing wood with a cutting tool against the grain, various mechanical grips are often observed, which leave dents– depressions on the surface formed as a result of local compression of wood, as well as scratches– surface damage in the form of a narrow long depression.

As a result of the gouge cutting edge tools are formed scallops– areas of the untreated surface in the form of a narrow strip protruding above the treated surface.

When sanding the surface of wood, sometimes a defect such as sanding– removal of part of the wood below the level of the treated surface.

With increased friction of cutting tools during wood processing, a defect such as burn wood in the form of a darkened area of ​​the treated surface.

The above wood defects reduce the quality of processing, affect gluing, finishing and veneering of the material or the entire product, in some cases worsen the appearance and violate the integrity of the wood, impair mechanical strength and complicate use.

This article will introduce one of the most important resources used in construction - wood. Wood is the inner part of a tree, located under the bark. Wood is widely used in industry and everyday life. Its high hardness, density and strength are key factors. But in the selection of quality material there is whole line defects, which means wood defects.

Let's focus on the main ones:

Wood defects shortcomings, features and defects of wood, both the entire trunk and its individual sections, which are various deviations from the norm, are named. Existing deviations reduce the quality and value of wood and limit its practical use.

Primary and secondary wood defects

Typically, defects are formed when a tree grows in unfavorable conditions, when the trunk is damaged by pests (wood grinders, bark beetles, etc.) or fungi, or when the fibers are rotting (see figure). These are primary wood defects that occur during the overall growth process of the tree.

Mechanical defects of wood. Processing defects

Deviations from the ideal structure occur during logging, for example, poor-quality felling and an incorrectly chosen direction of tree fall, causing the butt to split. During the processing process, mechanical defects in wood are revealed - these are processing defects. They are distinguished in the following types: wane, risks, and damage of a local nature, for example with a saw, is called a cut, waviness, fluffiness, mossiness, scuffing, gouges. A torn end is characterized by the presence of small indentations, tufts or small particles of wood, or burrs on the end of the part. Mechanical defects also include: flake, chip, dent, grinding, occurs fringe continuous and intermittent - ribbons of bundles of fibers or wood that have not completely separated on the edges of the parts, burns.

Lumber products change shape when stored, dried, moistened or sawed. These changes are classified as warping and have different degrees (see figure).

Lumber is also subject to defects - rot, cracks, wormholes, which are secondary defects that arise during storage and use of wood.

Features and defects of wood are divided into 9 groups of defects. The main ones:

1. knots;
2. cracks;
3. trunk shape defects;
4. structural defects of wood;
5. chemical stains;
6. fungal infections;
7. biological damage;
8. foreign inclusions, mechanical damage, processing defects;
9. warped.

Knots on a tree trunk

Bitches- This is the first of the groups that bears the main variety-forming defect, combining two types: knots and eyes. The woody content of the knots has a finer structure of the annual layers and a dark color; they are the base of the branches, which are enclosed in the wood of the trunk itself. Happens as a species open knot, so overgrown knot.

Overgrown knots They have no varieties and are found exclusively in round materials.

Defects associated with the shape of the trunk

Trunk shape defects growing trees are distinguished in the following types:

1. conciseness;
2. backbone (ribbed and rounded);
3. ovality;
4. growth;
5. curvature (complex and simple).

Curvature(see figure) is a versatile or unilateral curvature of the trunk along its entire length. There are simple and complex (several bends in different directions) types of curvature, which make sawing difficult and produce a lot of waste.

Zakomelistost(see fig.) when sawing gives Not quality material, the appearance of a large number of cut fibers. This is a thickening of the butt of the trunk in relation to the entire trunk.

Royki– this is a ribbed butt, when cut transversely at the end of the trunk it looks like a star-lobed arrangement of annual fibers. This material is highly warped and has reduced strength.

Growths on the trunk are accompanied by curling of the wood, which is more common in deciduous trees - this is a local sharp thickening of the trunk.

Surges most often found on the butt part of the trunk. Accompanied by smooth growths on the surface. Mouth guards expressed in a more prominent form, arising in places of dormant buds, look in the form of drops.

Wood structural defects

Defects in the structure of wood (see figure) are divided into the following types: roll; fiber inclination; traction wood; curl; curliness; pockets; eyes; core, double and mixed core; germination; stepson; cancer; dry side; tarred; false nucleus; internal sapwood; spotting and cross-layering. Let's look at the main types.

Cross-layer characterizes the different direction of deviation of the fibers from the axis of the tree. The lateral load of such wood is poorly perceived. Curlyness refers to a type of fiber inclination - a wavy arrangement of fibers. Curl– this is the curvature of the local character of the annual layers.

Kren occurs more often in coniferous wood, changes in structure occur in compressed areas of the trunk and branches. These are arched areas that form in curved trunks or obliquely growing trees. There is a displacement of the core during cross cutting. This defect contributes to the warping of boards and beams, reducing the strength and uniformity of the material structure.

Double core clearly expressed when cross-cutting a log. The tree trunk in this place most often has an oval shape. Between the cores it is usually observed germination in the form of overgrown bark. This deficiency leads to cracking, processing difficulties and increased wood waste.

Internal sapwood expressed at the end of the trunk in the form of several or one ring-layers of different widths, having a lighter color than the core of the wood. This group of annual layers in the core of wood has the properties, structure and color of sapwood. This defect is characteristic of deciduous trees, often found in ash and oak.

False core is the inner part of the trunk with a dark color in different shades. Shapes include round, lobed, star-shaped and eccentric. The darker color of the false heartwood differs from the sapwood.

Pocket is a cavity filled with gums or resins located inside the annual layers. Such resin pockets reduce the strength of wood, spoil the surface and are not amenable to gluing and finishing.

At curliness wood fibers are placed wavy, especially at the butt of the tree. This material is highly valued when molding sliced ​​veneer, but the processing process itself is difficult to handle. This defect is characterized by the formation of growths and swellings at the root part of the trunk.

Sprouting called a defect in a separate area that appears as a result of mechanical damage (tarring, mushroom spots). In this case, not only the appearance deteriorates, but finishing becomes more difficult.

Curl– this is the curvature of the annual layers due to the influence of trunk knots or shoots. They can be one-way or end-to-end. This defect reduces strength, so it is not used in the manufacture of parts that carry additional load. Defects such as resin pockets, tar and heel are characteristic of the group of coniferous species.

spotting- these are strips colored differently than the entire body of the trunk, which do not affect the hardness of the wood. Spotting appears during tree growth.

Grinding This is a section of softwood material that is heavily impregnated with resin. Places are darker in color. Resin has no effect on strength and is less susceptible to rotting, but makes the overall finishing of the material and painting more difficult.

Chemical coloring of wood

Chemical wood stains- these are unnaturally uniformly colored areas in wood that arose as a result of the development of biochemical and chemical processes, in most cases this is associated with the process of oxidation of tanning components. usually found in upper layers wood When the material dries, they most often fade.

Fungus can grow in wood

Fungal lesions- this is a group of defects that occurs with the participation of fungi, which can either cause the destruction of wood or not at all affect its strength, but have the property of changing color.

There are only 6 types of such fungal infections: mold, mushroom sound spots, sapwood mushroom stains(color spots – dark and light, deep, superficial and sublayer), browning(lateral and end), rot And hollow.

Mold has the appearance of a continuous coating or stain on areas of the wood surface. It appears during damp storage of timber and colors the surface of the wood pink, black and other colors, which depend on the color of the mycelium and spores.

Fungal sound spots do not reduce the strength of wood, they arise in the core of the tree under the influence of wood-destroying and wood-staining fungi. Identified in various types– rings, holes, a continuous affected area in the center of the trunk, often extending to the periphery.

Sapwood mushroom stains– these are areas of colored sapwood affected by a wood-staining fungus that does not cause rot in felled wood. It is noted in the form of stripes, elongated spots or entire surface lesions. These colors are characteristic of coniferous species. Fungi cause blue, greenish or gray coloration. Light colors do not mask the wood texture, dark colors of sapwood color it dark colors and mask the texture. Deep sapwood colors penetrate into the texture to a depth of more than 2 mm, and sublayer colors are located at some distance from the general surface.

Browning affects deciduous trees with a brown color. In felled wood, biochemical processes occur that reduce the hardness of the wood. The brown color during end browning originates from the end and goes along all the fibers. Lateral browning begins from the side surface and spreads towards the center of the timber.

Rot- these are areas of wood that are abnormal in overall color, which may or may not reduce the hardness of the material, arising from the influence of wood-decaying fungi. The first stages of fungal infection do not change the quality and value of the wood, but only change the color of some areas.

It has several varieties, distinguishable by color and structure: variegated sieve, brown fissured, white fibrous.

The types are distinguishable in the following types: sapwood (soft and hard), external rotten and sound.

Variegated sieve rot is characterized by reduced hardness and variegated color. Such wood retains its integrity for a long time, later it becomes soft and splits. Brown cracked rot causes cracking of the material along and across the fibers. White fiber rot attacks lignin and cellulose and discolors the wood in a marbled pattern. When severely damaged, it easily splits and crumbles.

The type of sapwood rot has pinkish-brown or yellowish-brown hues in softwoods, and a marble-like pattern in hardwoods. The hard type of this rot is close to the same hardness as the surrounding wood. Soft sapwood rot has reduced hardness.

External rotten rot occurs both in the sapwood part of the timber and in the core. This brown, cracked rot occurs during improper and long-term storage under the constant strong influence of wood-decaying fungi.

Core rot occurs in the core of a tree during growth and is characterized by reduced hardness. The first stages of such rot do not affect mechanical performance. Appears in the form of elongated spots or stripes.

Biological damage

Other and rare

Foreign inclusions imply the presence of a foreign body in materials that is not of wood origin (nail, stone, wire, metal fragment). Externally, this presence can be determined by the following signs: folds or swellings of the bark, dents, holes, changes in the color of the surrounding wood. Such defects require additional processing of the timber.

Defects in harvested wood are defined throughout the world as certain, detectable defects in the trunk. These defects can generally limit the scope of required use of the workpieces and reduce the grade of lumber. Certain defects can be detected even during the first external, careful examination. Some disadvantages of wood completely minimize the possibility of its further intended use, others only limit it.

All defects of the external and internal parts of the tree can be divided into natural, that is, those that arise during the growth stage, and those that form after production processing or storage of wood.

Natural defects of a tree gradually or quickly develop under the influence of causes of different nature and time of influence, this is unsuitable conditions weather in the area of ​​growth, random external impacts, unfavorable activity of insects and microorganisms, the aging process of wood.

The identified deficiency may affect the entire lumber differently. Some defects, such as rot along the entire trunk, are considered unconditional, that is, these defects will prevent you from using the wood where necessary. Other defects, for example, curls and knots located in a certain place, on the contrary, are highly valued by craftsmen.

Defects formed under mechanical influence on harvested wood are usually called processing defects. The quality of all wood can be negatively affected by storing harvested tree trunks or storing them incorrectly. The grade of the material depends on the defects identified by specialists, so the defects are determined according to GOST 2140-81.

Learn more about the types of wood defects in the video:

Rotting

Rotting is understood as a negative process expressed by the decomposition of wood fibers. Rotting occurs due to certain activities of mold, fungi and pathogens with a destructive effect. Rotting can occur even while the tree is growing; identifying such defects reduces the value of the raw material, since it implies damage to its layers and the development of various wood diseases.

Mainly, the development of putrefactive processes is promoted by higher than normal humidity. Rot in wood affects its environmental friendliness and reduces the quality of workpieces in production to three points or less.

In the initial stage of its development, rot is determined by the appraiser by the changed color of the wood and by a decrease in its strength. Then gradually the affected area is destroyed and transformed into dust. Often, after cutting down a tree, a completely internal rotten part of the wood is discovered, although outside there may be no changes.

Rot in the core is caused by the development of certain microorganisms that penetrate into the middle part of the trunk through wounds and knots. Thus, pathologically altered wood is not suitable for making the necessary lumber, but often, after some additional processing, it is used to create artistic products that are unique in appearance.

Dry rooms and a good ventilation system protect the harvested wood from rot. Harvested lumber is subjected to processing with special antiseptics and impregnations.

Different types of wood rot

Defects of wood. Defects are violations of the correct structure of wood and natural damage in the conditions of its growth, storage and operation. Defects disrupt the uniformity and integrity of lumber, reduce the strength of wood, increase its warping and cracking, complicate mechanical processing of wood, increase the amount of waste, and worsen the appearance of products.

Bitches there are open and overgrown (depending on whether they extend onto the side surface of the round assortment or not); round, oval, oblong (depending on the cross-sectional shape on the surface of the assortment) (Fig. 3.10); seam, edge, edge, end, stitched (depending on the position in the assortment); scattered, grouped, branched (depending on the relative location); fused, partially fused, unfused, falling out (depending on the degree of fusion with the wood); healthy (light and dark), healthy with cracks, rotten, rotten, tobacco (depending on the condition of the wood of the knot: tobacco knots indicate the presence of heart rot in the wood, since in round timber the rot can be hidden and not extend to the ends); one-sided and through (depending on whether they intersect through the flat assortment or not).

Cracks(Fig. 3.11) there are metic (radial cracks directed from the center to the periphery of the trunk), simple and complex metic (depending on whether traces of the crack remain at the ends of the assortment in the same plane or not); frosty (radial cracks directed from the periphery to the center of the trunk), accompanied by the formation of characteristic growths on the trunk; shrinkage cracks (radial cracks that appear during the drying process), differing from metic and frost cracks in their shorter length and depth; peeling (arc-shaped or annular cracks between the annual layers).

Convergence- narrowing of the trunk exceeding 1 cm per 1 m of length.

Zakomelistost- a sharp increase in the diameter of the butt part of the trunk; It can be round and ribbed.

Growth- sharp local thickening of the trunk.

Curvature the trunk can be simple and complex.

Kren- apparent thickening of late wood of coniferous species in the compressed zone of the trunk, curved or inclined tree. The similarity between heelwood and latewood is purely external, since heelwood has a completely different anatomical structure. There is a local roll, which affects one or several annual layers, and a continuous roll, which covers half or more of the cross-sectional area of ​​the trunk.

Fiber inclination - non-parallelism of the fibers of the longitudinal axis of the assortment .

Curly - twisted or random arrangement of wood grains . There is a wavy and tangled curl.

Double core- presence of two cores in the assortment .

Resin pocket - a cavity inside the annual layer filled with resin.

Germination - overgrown deadness of a section of the trunk. There are open and closed sprouts.

Chemical stains arise in felled wood as a result of chemical and biochemical processes associated in most cases with the oxidation of tannins. Chemical colors are uniform in color and are usually located in the surface layers of wood with a thickness of 1...5 mm). As the wood dries, they often fade to a greater or lesser extent. The chemical colors include the following: produbina - reddish-brown or brown color of the subbark layers of driftwood of species whose bark is rich in tannins (spruce, oak, willow, etc.); tanning drips - brown spots in the form of drips on the surface of assorted species, the wood of which is rich in tannins; yellowness - a light yellow color of the sapwood of driftwood of coniferous species that occurs during drying. Chemical stains do not affect the physical and mechanical properties of wood, but intense colors spoil the appearance of products.

Mushroom sound spots and streaks - areas of abnormal coloration of the core (real, false and mature wood) without reducing the hardness of the wood, which appear in a growing tree under the influence of wood-destroying fungi (the first stage of damage). They do not significantly affect the mechanical properties of wood, but they spoil the appearance and increase the water permeability of wood.

Core rot- areas of abnormal coloration of the core (real, false and mature wood) with reduced wood hardness, which appear in a growing tree under the influence of wood-destroying fungi (second stage of damage). Heart rot significantly deteriorates the quality of wood up to its complete technical unsuitability.

Mold- mycelium and fruiting of mold fungi, which most often appear on damp sapwood during timber storage. Mold appears as a surface coating of blue, green, black, pink or other colors. Mold does not affect the mechanical properties of wood, but deteriorates its appearance.

Sapwood mushroom stains - abnormal coloring of sapwood without reducing its hardness. This defect occurs in felled wood under the influence of wood-staining fungi that do not cause the formation of rot. Therefore, the mechanical properties of wood do not deteriorate, but its appearance deteriorates and water permeability increases.

Browning- brown color of sapwood different shades, varying intensity and uniformity. Browning occurs in felled wood as a result of the development of biochemical processes and causes a slight decrease in the strength of the wood.

Sapwood rot - abnormally colored areas of sapwood without or with a decrease in wood hardness. Sapwood rot occurs in dead, dead and felled wood under the influence of wood-destroying fungi and spreads deep into the wood from the ends and side surfaces.

External rotten rot - areas of abnormal color, structure and hardness of wood that appear in timber during long-term storage under the influence of strong wood-decaying fungi. External rotten rot is characterized by a brown color of various shades and a fissured prismatic structure. Affected wood easily falls apart and is ground into powder. Affected wood is a dangerous source of fungal infection for various wooden structures.

Wormhole - passages and holes made in wood by insects. If the wormhole comes out on two opposite sides of the assortment, then it is called through.

Wood defects. Mechanical damage of artificial origin is called defects. Wood defects include foreign inclusions (stones, sand, wire, nails, metal fragments, etc.); mechanical damage by tools and mechanisms during its harvesting, tapping, transportation, sorting and processing (bark peeling, hacking and sawing, punishment, flake, chipping and tearing, gaff punctures); charring; cut bevel - non-perpendicularity of the end of the longitudinal axis of the assortment; wane - a section of the side surface of the trunk, preserved on edged lumber(Fig. 3.16); zakorina - a section of bark preserved on the surface of the veneer; cutting defects are risks (traces of teeth of saws, knives, etc.), waviness (non-flat cut), hairiness and mossiness (tearing of individual fibers), veneer ripples (different levels of wood fibers), burrs and gouges, fringe (tufts of incompletely separated fibers on the ribs of the assortments), burn (from friction with a cutting tool); warping - curvature of lumber products during sawing, drying or storage.

Lumber is widely used in construction and finishing, but it can have various defects and defects. Of course, you always want to choose the highest quality material, beautiful and reliable, that is, ideal. But in order to make such a choice, you should at least imagine what kind of defects lumber may have, and what you should pay attention to when choosing them. Today we will tell you about possible defects wood and finished lumber.

Let us note that defects in lumber can be divided into two main types - natural, that is, related to defects in the wood itself, and those that appeared during wood processing, in the process of creating lumber, that is, depending on the human factor. In Russia, the special GOST 2140-81, developed back in 1981, is currently still in force. This GOST includes all visible wood defects.

The most common defect in lumber is the well-known knots. Actually, this is a part of the tree that ended up inside the trunk, which did not have the best effect on its quality and appearance. Although sometimes knots can even decorate the cut of a tree, experts try to avoid such options. There are many types of knots that can end up in lumber:

1. Round, oval, oblong.
2. Depending on their location in the sawn wood, knots can be edge, stitch, edge, face, or end.
3. There are through knots, passing through the entire lumber, and one-sided knots.
4. Branched, grouped and scattered knots over the entire surface of the lumber.
5. Knots that are not fused with the surrounding wood, fused or partially fused knots.
6. Rotten, tobacco, decayed and healthy branches.

It is worth noting that not all of the above types of knots have a catastrophic effect on the quality of lumber. For example, if a knot is completely healthy, fused with the rest of the wood, then it stands out only externally and will not affect the quality of the lumber. But a stitched knot, that is, a knot that penetrates the entire edge or face, extending onto two edges, is very bad. Experts also consider group knots, that is, those located close to each other, to be very harmful to the quality of lumber.

The second common defect in lumber is cracks. They represent a break in the wood; cracks are much more common along the fibers, rather than across them. In small assortments, it is not practical to distinguish cracks by type; they are considered a single defect. In large assortments, the following types of wood breaks can be distinguished:

• These are radial cracks inside the trunks. Most often found in beech, larch and pine. They can reach 10 meters, often the crack runs from the butt to the living crown. Methic cracks are not visible on the side surface of round pieces of wood, but they can be noticeable on the ends of lumber. There are simple metic cracks and complex ones.

1 - simple metic; 2 - cross-shaped metic

• Peeling cracks. They represent breaks in the annual layer of wood and are found in all tree species. A crack is an arched or annular crack not filled with resin.

• Frosty cracks. As the name implies, they appear during a sharp drop in temperature in winter and spread radially into the depths of the trunk.

• This is the case when the cause of the crack is human intervention. Such cracks occur during drying of wood as a result of drying stresses. They are smaller in length and depth and usually appear on the ends of lumber due to uneven drying.

It is also customary to distinguish between end cracks, lateral cracks, deep cracks and not, through cracks, closed cracks and diverged cracks. The appearance of cracks significantly reduces the strength of the wood; in addition, fungi, mold, and moisture can penetrate into the lumber through the cracks. Therefore, breaks, especially deep and clearly visible ones, are considered a serious defect.

GOST also indicates the presence of defects in the tree trunk itself, which can ultimately affect the quality of lumber, make its preparation more difficult, and consumption much more significant. The following trunk defects are distinguished:

• This is a decrease in the diameter of the tree from the butt to the top. In general, this is a normal phenomenon, because the trunk is always thinner at the top. But if the diameter decreases by more than a centimeter for every meter of height, this is already a defect.

• Compulsiveness. One of the types of camber is that the trunk is noticeably wider at the bottom. The backbone can be rounded and ribbed.

• Ovality. The shape of the end of round lumber in the form of an ellipse is also considered a defect.

• Growths, that is, thickenings of the trunk, can be lumpy or smooth.

• Curvature. It is noticeably more difficult to work with a curved trunk, and the bends can be simple or complex.

The indicated trunk defects can ultimately cause a radial inclination of the fibers in already prepared lumber and veneer.

There are also many defects in the structure of wood:

• Tangential fiber inclination, which is informally called natural cross-bed. In this case, the wood fibers are arranged either at an angle or in a spiral. Cross-layering can cause warping and increased longitudinal drying.

• or radial inclination of fibers. It can occur due to improper cutting of generally normal timber or due to the curvature of the trunk and burrs.

• Kren. These are changes in the structure of branches and trunk, characteristic of coniferous species. It is expressed in darkening and thickening of the annual layers, leads to the appearance of cracks, reduces the strength of the wood and interferes with its processing. The appearance of the lumber also deteriorates.

• Wide layering. Too wide tree rings, such wood is softer, it is fragile.

• Too thick, sharply enlarged annual rings are expressed in hairiness, sometimes the wood changes color. May lead to cracks, warping, and mossiness.

• Curlyness. The wood fibers are arranged randomly and tortuously. This material is fragile and more difficult to process. But in finishing lumber, twisting is even valued for the unusual appearance and structure of the tree.

• Curls on annual layers. They reduce the strength of the wood; the curls can be through, that is, extending onto both sides of the lumber.
• Eyes. They can be dark and light, clearly visible and not very visible, scattered and grouped. In general, these are traces of dormant buds that never became shoots. Eyes are not usually considered a serious defect.

• This is a cavity that appears between the annual layers and is filled with resin. It is inconvenient that the resin flowing from such pockets stains the instrument and spoils the surface of wooden products.

• Wrong core wood, offset or double.

1 - displaced core; 2 - double core

Wood wounds include dry side, sprouting, and cancer. All these are serious lesions that affect both the appearance of the wood and its quality.

1 - open cancer; 2 - closed cancer

During wood processing itself, in addition to the cracks that we wrote about above, the following defects may occur:

1. Change in wood color. This can happen if hardwood is dried at too high a temperature. high temperature. Often, a burn can even occur on the tree.
2. Changing shape. Of course, during drying the wood will still change its shape, but you can ensure that the changes are minimal. To do this, you should strictly adhere to the drying technology and act carefully.
3. Tarting. If there were resin pockets or the wood itself was resinous, then the resin at a high temperature - above 60 degrees - would simply flow. Overall on technical properties Wood resining will not be affected.
4. Cell shrinkage. We note again that you should not dry wood at temperatures above 60 degrees, as this will have a detrimental effect on its properties.
5. Warped. It can occur not only during drying, but also during improper storage and sawing.

In addition, tanning and chemical processes can cause wood to become abnormally colored. This phenomenon is called chemical coloring, physical properties the wood does not change, but the appearance is seriously affected.

Fungal infections of wood and biological damage, such as wormholes, are very harmful. In addition, defects in lumber may appear during transportation as a result of careless handling, improper cutting and processing. This is also a human factor.

Mechanical damage to lumber, for example, nicks, scratches, punctures, chips, tears, dents, snatches, often occurs during manual processing. Automation of the process and the use of special devices when cutting and sanding wood help to avoid such problems.