Foreign inclusions, defects, wood defects - all these flaws sufficiently reduce the quality of the material. Naturally, such raw materials cannot be used for any construction purposes. For this reason, you need to know what are the disadvantages of wood, as well as which ones and how to fix it.
General description of defects
To begin with, it is worthwhile to deal with what is, in principle, classified as a wood defect. These are various kinds of flaws that arise on the material due to exposure to weather conditions, mechanical stress, the presence of biological pests or any other factors.
It is also worth noting that these flaws are not always necessary to eliminate, it all depends on the purpose for which the material is used. Of course, in woodworking, such defects degrade the quality and complicate the processing process. In woodcarving, for example, some flaws do not interfere with work at all, and according to artistic designs, they can also be part of the pattern.
For these reasons, anyone who plans to work with wood needs to know what defects the material may have, which ones are dangerous and which are not. To begin with, it is worthwhile to understand the general classification of wood defects:
- knots and cracks;
- defects in the shape and structure of the trunk;
- biological and fungal flaws;
- foreign inclusions or chemical color;
- mechanical damage, warping, etc.
It is important to note here that mechanical defects include not only those that were originally from the tree, but also those that may occur during processing, transportation, sorting, etc.
The first type of flaw: knots
First you need to decide what it is. Knots are parts of branches, or rather their bases, enclosed in wood. However, not all so simple. To date, seven different types of this deficiency are known. Types of wood defects:
- The first species is distinguished by its position. They can be plastic, that is, going to the surface of the board or bar. Can be edge, that is, located on the edge of the board, can also be edge or end. If the cross section of the knot goes through the entire cavity and is present at two ends at once, then it is cross-linked.
- They can differ naturally in their form. Distinguish round, oval or oblong.
- The degree of overgrowing also differs. They can be either overgrown or open.
- Separately, the degree of intergrowth also stands out. They can be either fully fused or partially. There are also dropdown types. This means that the knot is practically not connected to the surrounding wood.
- They can also be one-sided or through.
- Depending on the state of the wood, the state of the knots also changes.
Wood defects and defects for the quality of lumber are the worst enemies. Sometimes knots are pretty hard to tell. For example, the horn type is distinguished by the fact that the tree itself is healthy, but some areas are very saturated with tar and tannins. Due to the resin, they have a darker color, as well as increased strength. However, if you dry the product with such a flaw, the knot will simply fall out and a hole will form.
There may also be weakened knots. This means that around them the tree is still healthy, but now they themselves are already starting to rot. At this stage, the knot can still be quite solid and maintain its structure, but its color is already noticeably changed. The loose type of knot means that the material around is healthy, but a certain area either completely or partially has lost its structure and is already too soft. The last type is a tobacco knot, which has completely lost its hardness and structure, has acquired a rusty-brown color that resembles tobacco and, when touched, turns into powder almost immediately.
Second type: crack
A crack is the breaking of wood fibers along their location. Just like knots, they are divided into several types. They differ in their position, depth, width and type.
Such a wood defect as a crack can be of a metic type. This type is characterized by the fact that one or several cracks pass inside the trunk through its core in the radial direction, but do not affect the periphery. Most often, such cracks extend upward from the butt. In addition, during drying, they usually increase even more in size.
Frost cracks may occur. They are characterized by the fact that they also extend in the radial direction, but from sapwood to the very core of the trunk. There is a defect in wood called cracking shrinkage. This means that due to uneven drying of the material, cracks appeared that will increase, penetrating deep into the lumber.
Barrel-shaped flaws
In this case, all the flaws are natural in nature and arise in the process of improper tree growth. They can also be of several different types.
The first defect of wood of this species is called stiffness. This implies a sharp and disproportionate increase in the diameter of the butt portion of round lumber. Another drawback is the lack of availability. This means that wood, on the contrary, is unevenly and not according to the rules decreasing in size, or rather, in diameter. It is generally accepted that the normal drying of a tree is 1 cm per 1 m of lumber. If the value is exceeded, then this is a flaw.
Another unpleasant drawback is the growth. This is called a sharp thickening on a tree trunk. The shape and size of such growths can be very different. Most often, such a defect occurs in deciduous trees. Naturally, curvature also belongs to defects of wood of this kind. By this is meant the curvature of the axis of the lumber. Due to this drawback, the amount of waste is significantly increased during processing.
Longitudinal recesses in the butt part of the trunk are called roars. If you cut in this part of the wood, then it will look like a star, and the location of the tree rings will be wavy. Most often, lumber obtained from such a tree, almost all goes to waste. This is due to the fact that the material will warp too much, and the strength will be greatly reduced.
Tree structure
Quite often it happens that defects and defects of wood lie in its very structure. In addition, there are quite a lot of them.
Incorrect tilt of wood fibers may occur. This means that some fibers are not parallel to the longitudinal axis of the trunk. Such a slope may be of radial or tangential type, depending on which angle. The presence of such a disadvantage greatly complicates the process of splitting, as well as machining.
Another drawback is quite common in hardwood and is that the width of the annual layers of the tree is significantly and locally increased. The occurrence of such a problem leads to the fact that it is necessary to more thoroughly dry the lumber, and this is fraught with the appearance of cracks.
It also happens that the fibers are arranged in a helical arc with respect to the longitudinal axis of the material. This is called a cross-country. Here it can be noted that it can be either of natural origin or artificial, if the harvesting is not properly dried. Most often, when such a defect and wood defect occurs, it strongly warps it, which greatly complicates processing and increases the amount of waste. In addition, cutting such wood is much more difficult.
Sometimes there is such a thing as a resin pocket. It is found in coniferous wood. So called the formation of small cavities between the fibers of the material, which are filled with resin. Due to their occurrence, durability deteriorates and processing is difficult.
Defects from pests and wood defects: a description of fungi
Many people know that during the growth of a tree, a fungus can appear inside its structure. Naturally, this is a drawback. The thing is that the fungus is the lowest form. This means that in itself it is not able to produce nutrients for its life. He gets them by sucking from a tree. Currently, all types of fungi are divided into two types: wood-staining and wood-destroying.
If we talk about the first group, then this can include those pests that cause fungal sound spots or sapwood mushroom stains. The second type of mushroom is even more dangerous, as the result of their effect on wood is rot. You can also add that some of the disadvantages are caused by the impact on the lumber of both types of fungus at once. The most favorable environment for their development is a temperature of 15-20 degrees Celsius and from 30 to 60% humidity. When exposed to a temperature of 60 degrees, the fungi die.
It is worth paying special attention to sapwood mushroom stains. It is important to note that this drawback does not affect the mechanical performance of wood. However, the appearance of the workpiece is greatly deteriorated. In addition, the presence of such fungi on lumber always causes defects when varnishing wood. That is, when you try to paint or varnish the product, the layers will collapse upon contact with fungi. Everyone is quite familiar with mold and rot. Here it is clear that in the presence of such flaws, the tree most often becomes simply unsuitable for use.
Elimination of knots and cracks
It is worth saying that in fact the formation of knots is not so scary as it might seem at first glance. Small fused knots will not cause any trouble at all. Large and poorly held ones are likely to fall out over time. After this, however, there will be a hole, possibly a through hole, which will have to be eliminated.
The sealing of defects in the wood in this case is quite simple. It is necessary to drill a hole in the workpiece, in the place where the knot fell, but at the same time make it several millimeters more. A “plug” is cut from a board with the same thickness and structure, inserted into the hole and glued with wood glue. It remains only to add that around some knots there may be something like a black line. This means that the wood is affected by rot, which will continue to spread. Such material is better not to use at all.
Cracks are defects of wood. There are various ways to eliminate them. So, there can be several ways to solve the problem. If the crack is small, then it can simply be planed or puttyed. If the crack is large enough, then currently in the market of building materials you can buy a special sealant that can be used to glue the workpiece. Naturally, this is not an ordinary sealant. The first thing that it differs significantly is its compressive strength. Due to this, during deformation of lumber under the influence of high temperature, the substance is not squeezed out of the crack.
Wormholes and pitching
Eliminating wood defects, such as wormholes and pitching, is also real. As for the first problem, these are the passages that woodworm insects make in the array. It is easy enough to detect their activity, as small holes will be visible on the surface.
The whole problem lies in the fact that the damage can be minor and then they do not interfere with the work, but can be quite serious, which will lead to a complete rejection of such a workpiece. Only a professional can determine what type of damage. If such holes are found in the lumber blanks, then it is better not to buy them at all. If they were found in the walls of, for example, a wooden house, then you must immediately call a specialist who can treat the structure with good antiseptics. You can not hesitate with this, since these insects reproduce very quickly.
Pitching most often occurs in those places where the wood was damaged by the tool. This greatly reduces its strength and degrades performance. It is impossible to get rid of this shortcoming in any way if it appeared. This means that you need to be careful when processing wood so that they do not appear at all. This will be the best solution.
Fungus elimination
The only sure way to protect wood from these pests is through antiseptic treatment.
It is very important to note that it is necessary to start covering the funds with protective equipment before transportation to the construction site. The thing is that under suitable conditions, in just a couple of hours, the surface may turn blue. This means that a fungus has appeared. He will not reduce the strength indicators, but the appearance will greatly spoil.
This defect can be eliminated if you use a special chlorine-containing composition as a bleach. To protect the wood during transportation, special "transport" antiseptics are used. Their validity period is from 2 to 8 months, but they cost quite cheaply.
It is necessary to use compositions for protection with a sufficiently long period of validity after the materials have been delivered to the site or the structure has already been erected. It is important to note that preforms must be well cleaned and dried before they can be processed. Another important point is that the subfloor or logs, which often come in contact with moisture, need increased protection against fungus. Here you need to use a hardly washed away preservative antiseptic.
The downside will be that the structure of the lumber will acquire a greenish tint, but there is no better protection. If this is not done, then the boards will simply rot and there will be no protection from this anymore. Another important point is that not only the facade of the building is worth processing. It is necessary to carry out the same actions for protection inside the building, otherwise all work to protect the outside will be in vain.
Mechanical imperfections and foreign inclusions
It also happens that defects occur when drying wood. This is called warping. This means that during sawing, drying, cutting, or storage, the workpiece has greatly changed its original shape. Because of this, the processing of wood is very difficult, since its shape usually becomes too curved. In general, mechanical damage - these are the flaws that already arise as a result of human interaction on wood blanks.
These include defects that occur during cutting. Burns may appear on the wood, the cutter may accidentally cut the workpiece in an unnecessary place, etc. The presence of such defects greatly complicates the work of the cutter, since during processing it will be necessary to leave more material for allowances. Naturally, this increases the amount of waste and reduces the amount of suitable material. Wood processing defects most often lead to the fact that you have to abandon its use.
As for foreign inclusions, this implies the presence of stones, sand, glass, nails and other things inside the workpiece structure. Although it is fair to say that with the exception of nails, everything else has to be encountered quite rarely. The presence of such inclusions entails not only a complication of the processing procedure, but also a risk of ruining the tool during operation. In addition, the presence of inclusions such as nails causes a color change around their location. Usually this leads to the fact that such areas simply have to be cut.
As you can see, there are a lot of defects in wood processing. However, some of them can be eliminated quite easily, and the appearance of some can simply be prevented. For these reasons, this material is still common and widely used.