You may know what wood is and where it comes from, but what you may not know is how it is obtained. If so, stick around and we’ll explain everything you need to know about wood procurement and processing.
The process to obtain wood in 7 steps
The process of wood procurement or transformation covers from the commercial exploitation of forests -the raw material- to the production of wood in the form of planks that will eventually be used as a basic material in carpentry and construction.
Now, let me explain each of the 7 phases.
Phase 1 to obtain wood: Logging
This is the first step of the whole process to obtain wood and it takes place in forests, where the tree is cut down from its base using chainsaws or mechanical saws.
The age of the tree is fundamental for this procedure: if the tree is felled when it is very young, the wood will be excessively soft. On the other hand, when the cutting is done on a very old tree, there is a greater risk that the heartwood will be diseased or even rotten. To better understand what we are talking about, read the article on basic timber concepts.
Felling should be done in an orderly and sustainable manner so that the trees have time to mature and provide good-quality wood. Remember that trees need decades to reach adulthood.
In addition, indiscriminate logging is what has caused the end of forests and has left many species on the verge of extinction, as in the case of mahogany.
Sustainable logging methods
For this reason, sustainable logging methods should be used:
Partial logging
This procedure consists of dividing an entire forest into plots that are felled on a rotational basis, in order to cut the trees that are most suitable for felling (the oldest ones) and let the younger ones reach maturity.
Seedling trees
The idea of this method is to find out if the trees in the forest have seeds that can develop easily, that is, seeds capable of producing new trees.
Then, if the seeds are good, the felling process can go ahead as long as some trees are left scattered throughout the forest to help the species reproduce.
Selective logging method
In this process, trees are felled and transported according to their size, maturity, and quality.
This increases costs since the process must be done by spreading the equipment and personnel throughout the forest, while only the best trees are sought for cutting; however, this wood preserves the environment in which the trees grow and ensures that those that are still very young have time to mature.
Conservation of the tree mass
The aim of this method is to cut only large trees that have already reached their growth limit or are very close to reaching it; at the same time, other smaller trees that are known not to grow much more are cut down because their trunks are twisted or have a defect in the fibers that prevent them from reaching a normal size for their age, that is, they will no longer have a normal height.
This reduces the number of trees in the forest and thus decreases the competition for nutrients, water and light among the trees that are still standing, making them grow better.
Pruning of branches
Another technique used is to cut certain branches so that the tree uses all its resources to produce more wood in the trunk, and the uncut branches are enlarged.
Phase 2 for obtaining timber: Forest pruning process
This phase is carried out by eliminating the branches located on the trunk of the felled tree by using tools such as saws. This is done to improve the quality of the wood.
This is why you must not confuse industrial pruning with gardening pruning, which is carried out on trees that have not been felled, and seek other objectives such as greater fruit production by the plant.
However, although it may seem simple, this process is very important because if the pruning is poorly done due to lack of experience or if it is done at the wrong time, it is very likely that the wood quality will be affected. Problems such as the following will surely appear.
Flaws caused by poor forest pruning
The 2 most common are the knots and the quinoa bags.
Let’s start talking about knots. First of all, remember that knots are only detrimental to wood as long as they generate gaps and loss of continuity in the material.
However, if they do not affect the structure of the wood, that is, if they are healthy knots, they are considered decorations since they add a natural design to the material.
In contrast, we have knots that are harmful to wood. Here we’ll see how they are classified
Classification by knot condition
Dead knots
These knots are the remains of branches that have not been cut properly.
They are formed by dead wood tissue that will give the wood a bad appearance in the future and will make it more difficult to work. They can change their surface since dead knots go in the opposite direction to the wood fibers, causing them to lose strength.
Live knots
Live knots appear when a branch received some kind of damage while the tree was still standing, such as an insect attack or a mechanical impact that caused a scarring process.
Then, when the healed branch is cut off marks appear on the trunk. These marks appear as patches of wood much darker than the rest. Therefore, they detract from the aesthetics of the tree and are quite difficult to remove, change the texture of the wood, diminish its workability and increase the resistance to cutting by saws.
Classification according to the size of the knot
Bird’s eye knot
These knots have a diameter smaller than 5 millimeters.
Small knot
These knots have a diameter between 5 and 15 millimeters.
Medium knot
Diameter between 15 and 40 millimeters.
Large knot
Diameter over 40 millimeters.
Classification of knots according to their shape
The knots will take a form according to the direction in which the wood is cut in relation to the trunk and the wood fibers.
Herringbone shape
When the wood has been cut in a radial direction to the trunk.
Round shape
When the cut was made tangential to the trunk.
Oval shape
When the cut was made in an intermediate direction between the tangential and radial axes.
Now let’s talk about the other problem derived from defective pruning: Kino bags.
Kino bags
These are accumulations of resin in the trunk of the felled tree that, if they become detached, leave holes and stains on the wood.
Besides all of the above, keep in mind that the more knots and Kino bags are found in a plank of wood, the lesser quality they will have and the lesser their commercial value will be.
Phase 3 to obtain the wood: Transport
This phase encompasses all the necessary procedures for moving the cut and pruned logs until they are sent to the sawmills, which are the facilities where the timber is left to be stored or sawn.
During this process, specialized machinery is used to transport forestry material; trucks with modifications to their chassis so that they can support the weight of the logs when they are stacked. Backhoes are also needed as they are often required to make way for the trucks to enter the logging site.
In addition, equipment is needed to move the logs and put them inside the transports:
- Stands
- Chains
- Cables or ropes
Once the logs have been stacked and are ready for transport, they are moved by road, rail or water depending on the logistical conditions of the country where the process takes place. For example, transport is done by land in most countries, but in others, it is preferred by sea because it is a more cost-effective option. In short, transportation varies from country to country because the regulations are different.
Phase 4 to obtain the wood: debarking
The purpose of this phase is to free the trunk from any substance or object that could damage the wood, such as stones or bark residues. In addition, this process has another very practical use as it extends the useful life of saws, bandsaws, and other tools that are in contact with the wood.
Likewise, the debarking process serves as:
- Facilitator of sawing.
- Control of pests in the bark.
- Accelerator of drying.
We must also take into account that this is the first phase that is done directly in the sawmill. There, an industrial tool called a roller chain, which has metal blades arranged as teeth that remove the bark from the trunk, is used. This machine is in charge of the whole process.
Finally, the bark and branches that were removed will be used for other applications such as the production of medicinal products, among other uses.
Phase 5 to obtain wood: Log splitting or sawing
This phase begins by automatically sorting the logs according to their diameter to ensure the best performance in the transverse and longitudinal cutting lines so as to obtain square pieces of wood.
The cutting quality is everything; the slightest deviation, even a few millimeters, can cause curvatures in the wood that prevent the pieces to be assembled. For this reason, every cut is checked to ensure that the dimensions are correct.
Types of woodcutters
Woodcutters are usually available in three different versions in a home environment.
Hand pump
It is a hydraulic jack that squeezes the piece of wood from one end by injecting columns of pressurized air. At the other end, the piece of wood is pressed against a metal wedge, causing the piece of wood to break into smaller pieces.
This is the most economical option, but it is a time-consuming process designed for cutting smaller amounts of wood.
Electric cutter
It is similar to the manual pump; however, instead of being activated manually, this tool is powered by a motor that generates tons of pressure by means of a hydraulic ram that falls on top of the piece of wood. Thus, the pressure splits the piece into smaller parts.
Obviously, it is more practical and faster than the manual option, but it is much more expensive and relies on a source of electrical power, battery, or generator.
Gasoline-powered cutter
It works in the same way as the electric cutter but it is powered by a gasoline engine. In addition, it can break larger pieces of wood.
Industrial woodcutter
In sawmills, woodcutters are much larger machines powered by extremely powerful engines. These machines are capable of cutting huge pieces and, by means of computers, it is possible to size the pieces.
Therefore, the logs are cut in the form of planks that are dimensioned for the commercial uses that are required.
Commercial wood forms
At the end of the sawing process, the main commercial forms of wood are obtained. These are the most common.
Strips
Long, square, or rectangular-shaped cuts of wood.
Planks
Imagine that you have a lath but it is visibly longer and thicker, this piece of wood is known as a plank.
Moldings
Moldings are made from battens and are also long but usually have more varied shapes. They are widely used in decorating and in the manufacture of furniture and doors.
Solid boards
These pieces of wood are flat and rectangular. Regular lumber boards are made from solid boards.
Sheets
These pieces are made up of very thin laminates that cover lower-quality pieces of wood.
Phase 6 to obtain the wood: Drying
The purpose of this process is to reduce the humidity present in the wood so it can be worked. Do you remember the concept of humidity?
Just in case we are going to remind you.
Moisture is the water vapor in the air and wood absorbs or releases moisture depending on its environment.
This is important because wood changes in consistency and above all lose strength the more humid it gets. So to work with wood you need it to be dry, but remember that technically any wood with a humidity of 12% or less is dry wood.
Now, let’s see what you get out of the drying process:
- Minimize the risk of wood changing its dimensions.
- Prevent the wood from being attacked by insects, fungi, and bacteria, i.e., the useful life of the material is extended.
- Reduce the humidity percentage to a value less than or equal to 12%.
- Reduce the weight of the wood, to save transportation costs.
- Increase resistance.
Types of wood drying
Now, let’s take a look at the types of drying available.
Natural drying
Once the wood is cut, it is stored in a place sheltered from rain, direct sunlight, and humidity. The arrangement of the wood must ensure that there is a good flow of air in the storage place so that the evaporation of water is more effective.
However, the main drawback of this method is that it takes too long to complete; from months to years depending on the wood.
Artificial drying
Unlike the natural process, this drying method gives excellent results in a short time but it is much more expensive as it requires equipment that is only available in industrial facilities.
An example of such equipment machine such as drying chamber in which warm, dry air currents are injected over the wood. Likewise, devices such as drying chambers that operate with steam.
Mixed drying
There is a third drying option that consists of mixing the two methods just mentioned.
For example, there are pieces of wood that have been left to dry naturally for a few months and are then transported to industrial plants where the process is accelerated by means of drying chambers.
Although this mix of methods is more economical than artificial drying alone, it is costlier than natural drying since resources must be made available for transporting the pieces. Therefore, the drying technique will depend mainly on economic factors.
Phase 7 to obtain wood: Planing
The planing is the last step in the process of commercial wood procurement and consists of eliminating any irregularities in it so that its final appearance is the best possible. In other words, planing is the step in which the wood is “polished” and given a good finish.
Irregularities are eliminated by means of processes such as the reduction and extraction of wood sheets with the objective of leveling and obtaining the necessary measurements so that the pieces can be used for the purposes for which they were designed.
Types of wood planing
Industrial planing
Done in the sawmill with an industrial planer, a machine that has steel blades arranged in sheets of wood that is used to cut very thin slices of wood “smoothing” the surfaces of strips, boards and other commercial presentations.
This is a fast and standard smoothing that has all the pieces that have just left the sawmill.
Manual planing
On the other hand, the manual process is carried out with a tool called a planer, which is an adjustable blade attached to a base by which it is held and its function is the fine cutting of the wood. The planer can be made of wood, which is lighter; of metal, which is more economical; or electric, the most expensive one.
This planing is usually done in a carpentry workshop; its objective is to give a personalized finish to the wood pieces that will be used to make furniture or more elaborate pieces.
The most important thing is that manual planing will depend on the type of wood, that is, the same technique is not always used and it is really an art that takes many years to master.
As you can see, the wood goes through a long and complex process from the time it is in the trunk of a living tree until it leaves the sawmill in the form of a plank or any other common form of presentation.
Now, you know how wood is sourced so you’re ready to get the one that best suits your projects.
See you next time.