3 Most Popular Types Wood Defects with Brief Discussion

Trees are a natural material and naturally acquire specific properties. Everyone prefers defectless, healthy, and wholesome wood for everyday use. All classes or species of trees have more or less the defect. These can be due to natural causes or soil defects. All these defects should be removed while collecting wood from the trees. We call it the wood defect if there are exceptions to the standard rules inside or outside the wood.

Due to wood defects, its beauty, durability, strength, and even practical value are reduced. However, if the wood is selected, it is possible to eliminate the defective woods from the beginning of tree growth to the use of wood at different times due to the irregular formation of tree cells for various reasons or naturally or artificially. The natural defect results from the irregular formation of the cob of the tree or any natural calamity (storm, lightning, fire, etc.). Artificial faults can be caused by carelessness when cutting down trees or due to conversion and use of wood or seasoning.

Due to the presence of water particles in the wood, the wood can be attacked by various insects or fungi, and the wood can rot and decay. Termites, moths, etc., also erode wood. Lack of wood preservation leads to decay or destruction. Therefore, by seasoning the wood correctly and using the necessary preservative coating, it is possible to protect the wood from all these erosions, decay, or destruction. The wood can be maintained for a long time.

Wood defects

Trees are a natural resource, grow naturally, and are shaped by soil, water and climate. As a result, changes are seen in the tree with different types of growth.

For example, the formation of branches, twisting of tree fibers due to wind or weather, abnormal growth of trees due to soil fertility, etc. Also, if there is carelessness while cutting the tree and there are defects in the drying work, there may be defects in the wood. There are two common types of defects in wood.

1. Natural defects, 2. Artificial defects

1. natural defects: The defect is called a natural defect when the plant grows during its lifetime.

  • Defects due to abnormal growth
  • Defects due to rupture to tissue
  • Defects due to wounds and injuries

2. Artificial defects: Defects caused due to drying, and the use of wood is called artificial faults.

  • Defects due to insect attack
  • Defects due to animal attack
  • Defects due to warping
  • Defects due to fungal attack
  • Defects due to checking slitting

Types of defects with sketch description

A. Defects due to abnormal growth: 

Many defects are observed in living plants due to abnormal growth. E.g.

  1. Rind gall
  2. Knot
  3. Grain
  4. Burr
  5. Compression wood
  6. Tension wood
  7. Constriction wood
  8. Interior wood
Rind gall

1. Rind gall: 

If the tree is injured during growth or due to various physical reasons, some part of the tree’s side grows abnormally on the trunk or branch. When there should be branches of the tree when the tree is cut down, the tree’s cutting place gets injured or injured, as a result of which the place becomes continuously swollen or growing in a crooked position. It is an abnormal growth of the tree.


2. Knot: 

It is a widespread defect in trees. The place where the branches come out from the stem of the tree The structure of that place is not like the original tree. A knot is formed due to the growth of cells there. Excessive pressure is applied to the area where it rains on the branched stems so that the cells in that area are more compact than in the latter, and the intestines become thicker and stiffer. Caution should be exercised when using git. There are two types of knots. E.g. A. Life knot and B. Dead knot.

life knot of wood
Life knot of wood
  • Life knot: It is the part of the tree branch that is intertwined with the stem while the tree is alive, and the branch receives nutrients from the stem even after death and is fully attached to the adjacent annual ring and is attached to the adjacent cell. Such knots are firmly attached to hard lateral wood. The color of the wood is brighter than the adjacent wood. It protects the continuity of the wood.
Dead knot of wood
Dead knot of wood
  • Dead knot: It is a part of a tree branch that is intertwined with wood but has no connection to the lateral cell. The consistency of the wood fibers is lost (Figure 6.3). They are loosely attached to the stem. After cutting the tree, all these joints become compressed and loose, and with a slight blow, it comes out of the wood. Dead knots are harmful to wood. A dead knot is very unsuitable for woodworking and reduces wood strength.

3. Grain: 

Wood grain is responsible for the strength, durability, beauty, etc. of the wood. As a result, the abnormal formation of the grain in the wood makes the wood weak. Grain can be of various types. E.g.

Spiral grain

Spiral grain: Usually, strong winds cause the tree to sway back and forth, causing the living seedlings to twist in the vertical part of the tree, and the effect can be felt even if the tree grows larger.

Diagonal grain
Diagonal grain

Diagonal grain: Although the wood is cut along straight fibers, when the fibers are not parallel to the wood axis (Figure 6.5), it is called diagonal fibers.

Waviness grain
Waviness grain

Waviness grain: In exceptional cases, the wood fibers are not straight or naturally aligned but curved or twisted vertically. It is challenging to operate a chisel on such fibrous wood, so care must be taken at work.

Cross grain: The fibers in the wood are not straight but horizontal. This destroys the durability and strength of the wood. Wood cannot be easily cut.

Up-set grain: If the tree breaks in the state of a sapling or too much pressure in the state of the sapling, then if the branch comes out again in this place, all the wood obtained from this branch and stem becomes scaly. When sawing wood, longitudinal fibers are cut, and the wood breaks under low pressure.

Twisted grain: If the tree is twisted or twisted for any reason while it is in a sapling state or the wind is blowing from one side, the sapling can also get twisted. This type of error is caused by the fact that every year new cells grow taller and larger than the previous cells, and new cells are scattered around the scaffold, and the cells are rolled either to the right or to the left. Rotten defective wood is challenging to cut and is useless to use. Much like twisted wood.

Interlocked grain: When a tree breaks during a storm or is severely injured while cutting a tree, the fibers inside the wood are turned upside down, and the fibers rise one on top of the other to form a new kind of fiber that looks a lot like strip weaving or hand fan weaving. This is the woven fiber.

4. Burr:

A particular type of chorionic gut wound is caused by the abnormal growth of dormant buds. These are bundles of corrugated wood fibers observed as large swollen joints on the stem (Figure 6.6). If there is a defect in the chopped wood, it is like a large swollen git on the wood, which is very valuable for making high-quality canines and home decor items.

Compression wood
Compression wood

5. Compression wood:

The wood of the softwood species, especially the Douglasfar, Pine, and Araucaria trees, has a darker color that resembles a red rod of a different color from the sapwood and looks a lot like manure wood. The wood on the trunk or branches of this type of tilted tree carries various structural features than usual. These are often called reaction wood. It is sometimes called Red Wood because it looks like a red rod. Since such wood originates on the compressed side of the tree, it is also called compressed wood.

6. Tension wood:

The texture, shape, and nature of compressed wood are similar to those of compressed wood. However, compressed wood grows on the branches of trees and the upper backs of sloping trees, and hardwood species, usually grown in tropical climates, are more likely to produce such wood. Seasoning causes the wood to shrink excessively and can cause the wood to twist and disintegrate.

7. Constriction wood:

When the vine on the tree’s trunk is patched, the trunk of the tree continues to grow. Then ERP wood is created. Due to creeper trees’ presence in this condition for a long time, the landscape of the trunk of the tree is reduced, and the system of this place becomes denser. Such wood is more wasted. The wood is not easy to use due to its grooves or holes.

8. Interior bark:

Due to the abnormal growth of some trees, the bark penetrates inside the stem, and a layer of wood surrounds the bark from all sides (Figure 5.6). Such an unusual structure and growth of wood occurs due to a special environment. Quite a few parts of the stem are seen to be this kind of defect. Such thick wood is not at all usable in thick or fence wood. However, the rest of the healthy and strong wood can be used by discarding the bark part of the big fence or thick wood.

B. Defects due to rupture of tissues:

Tree fibers become detached from each other, creating various cracks in the wood that can extend to some or all of the wood. If the tree is not cut down in time, the manure, the oil in the wood, the resin, the extract, and the moisture evaporates, causing the wood to crack and slowly come out. Such defects reduce the strength of wood and increase waste. Different types of cracks are discussed below. There are three types of cracks as-. A. Heart and star shanks, B. Radial shanks, C. Cup and ring shanks.

1. Heart and star shanks:

The shanks that arise from the marrow or center of a tree’s trunk and gradually progress to the circumference are called heart shanks. Again, when innumerable fissures are formed from the marrow, and the shanks together form a star, it is called a star shanks (Figure 6.9). When the cells in the center of the stem are compressed or dried up, and the tree swings from side to side in a storm, it causes heart shanks and star shanks.

Radial shank

2. Radial shanks:

This shank originates from a living standing tree’s perimeter and gradually expands towards the center (Figure 5.10). This type of fracture is caused by the contraction of the outermost part of the plant. Excessive heat, forest fires, etc., reduce the moisture in the tree’s outer cells, and the systems become detached from each other, causing cracks.

Cup shank

3. Cup and ring shanks:

The tree’s annual ring is formed, and these cracks extend from the particular part of the annual ring to the entire annual ring (Figure 6.11). This defect can cause the converted dry wood to split into several pieces along the edge and as a result of such cracks, the newly formed annual rings may become partially or wholly detached.

4. Hollow pith center:

Excessive aging of the tree dries out the various cells or sap of the tree pith, resulting in a hole in the wood pulp called hollow pith center.

C. Defects due to wounds and injuries: 

If any part of the stem is injured or any wound is caused during the tree’s growth, it gradually becomes a defect. Animals, birds, and people can break the bark of a tree, break branches in a storm, or injure a tree for various reasons. Below are the errors due to different types of wounds and injuries

  1. The covered part of pruned branches
  2. Exposed broken stalks
  3. Bark boils
  4. Alloys, dyes, ducts
  5. Mineral or metallic stripes, etc.

Pruned branches covered part: This type of defect occurs if tree branches’ pruning is not done carefully. Such defects weaken the wood and make the wood laugh at its mechanical properties.

Exposed broken stalks: The stalks of trees are broken in storms or winds, and the broken stalks are never filled. When filled, dead git or living git is formed. And when it is not filled, space is infested with fungi, and the wood rots or decays.

Bark boils: Removes wild animals or other animals’ bark and causes local wounds on the plant. The plant tries to heal the wound quickly through cell division. Due to the inclusion of an object in this time or condition, the wound site becomes swollen, called bark abscess. You may have to leave this space while working. This pairing results in dehydration of the wood and is infested by fungi at the wound site.

Basin, dyeing ducts: These originate from wounds created during plant growth. These are abnormal wounds on wood or tree trunks. Evergreen trees are found in different sizes of shale, which are filled with various liquid biochemicals. Resin is located like a tube in the stem And being long in size; and they cause severe damage to the wood.

Mineral or metallic stripes: Permanently zigzag or striped cuts of various colors are observed in the wood, termed as permanent tee of wood. These usually cause dark-colored stripes on the wood. This type of scarring is usually caused by the presence of minerals around the resin ducts. Moreover, many other types of stains are created in the wood. E.g., A. Foxiness, B. Dottiness, C. Druxiness.

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