Seasoning wood: Process, Types, Advantage

Seasoning wood: After cutting, when the tree is turned into lumber, there is a lot of watery part or sap in the wood, located between different wood cells. The watery part of sap in the wood causes decay in the wood, and the wood’s strength is lost. Wood is unsuitable for use by various fungi.

If you make any furniture or any other work with this juicy wood, it will cause cracks in the folds and create holes in the wood in a few days. You can use only the wood after extracting the sap from the wood, then the thing made of that wood becomes durable and intact. Therefore seasoning/drying of wood is required to keep the wood normal and usable.

Seasoning wood

The method by which it is possible to reduce or dry the water or sap, or moisture located in the wood cells and the cell wall is called seasoning wood. Wood sap needs to be controlled according to the difference and requirement in work.

Importance of wood seasoning 

Seasoning is done to dry the wood by removing the sap and water from the inside of the wood. It is also necessary to dry wood to achieve the following objectives.

  • The wood remains stable in the face of climate change as a result of seasoning.
  • The weight of the wood decreases from part to part.
  • Wood becomes robust, safe, and durable.
  • Prevent wood rot.
  • The wood is easy to work with, smooth, and easy to polish.
  • The wood-fibrous pattern, color-balance, and volume are reduced.
  •  Easily protect the wood from insects and spiders.

Types of seasoning wood/drying wood

There are various seasoning or drying wood methods, but only two methods are more prevalent for commercial purposes. E.g.

  1. Natural Seasoning/Drying 
  2. Artificial Seasoning/Drying 

1. Natural drying

Drying or seasoning that is usually done naturally is called natural drying. There are two types of natural drying, e.g.

  • Drying by air
  • Drying by water.
Wood Drying by air

 It is the traditional drying method among the conventional methods. It is commonly believed that the air’s heat comes in contact with the wood and turns it into water vapor inside the wood. In this method, the place is selected with a lot of shaded air to purify the wood, and the wood needs to be arranged so that the air can flow through the arranged pieces of wood and the pieces of wood are mostly exposed in an open place. 

So the wood drying in this method depends on the proper arrangement of the pieces of wood. Each piece of wood will be as wide or thick as possible. More space will be required for arranging the wood. The wood is arranged on a scaffold, as shown in figure. 

Air drying

According to the picture, the roof must be covered to protect it from sun, rain, and snow. It has to be paved under the scaffolding to protect from white ants and soil moisture so that it does not cause any damage to the wood. The wood is arranged on the scaffolding in such a way that air can enter inside each layer. Seasoning occurs due to ventilation, and the wood becomes dehydrated and dries slowly. This method takes about 12 months to 36 months to season the wood. 

Drying the wood in this way reduces the deformation of the wood. This method is the best of all the types of seasoning. In this method, you have to arrange a platform with some thick wooden blocks where the wood is arranged. The thick wooden blocks are called carriers. The wood is arranged on top of the carrier. A long strip of 3.6 cm wide and 1.25 cm thick timber is placed on the exterior timber at a spacing of about 6.8 cm to facilitate ventilation. This slice is called a sticker. Properly arranging the slice keeps the wood stays straight.

Wood stocks are made by placing planks and slices alternately. The wooden stock should be at least 4.5 cm above the floor or the ground. The height of the stock depends on the length and width of the wood.

For drying round wooden poles, logs or round wooden poles can be dried in open space by arranging rows one on top of the other about 30 cm above the ground or placing two horizontal poles on either side in the middle of each row. Since hardwood wood takes a long time to dry, the stock needs to be spaced more when sorting, and special care should be taken during drying so that fungi and insects do not attack the wood. Sometimes, you can get a good result by spraying the preservative solution on rows of stock of the wood by turning.

Water Drying 

This method is used for wood seasoning in most rural areas. It is the traditional method of wood seasoning in rural areas. In this method, the tree trunks’ bark is left in the form of logs and immersed in water for 3 to 5 weeks. The wooden logs are sunk in such a way that the sunlight does not get on the wood. As a result, the sap inside the wood is diluted and comes out and mixes with the water outside.

After the wood is lifted out of the water and arranged in layers under the tent, then it dries easily in the air. Figure 2.2). Seasoning can be done in less time with this method, even if some energy is reduced. In this method, the wood has to be wholly immersed in the flowing water or river water, or pond water for 2-4 weeks.

It will be very harmful to wood if partially submerged. Good results are obtained by keeping the thick side of the log facing the current of water. When the log is completely immersed in water, the juice inside it mixes with the water and comes out of the cell. The log has to be taken out of the water and left in a shady open place for some days to dry completely in air and heat. It is essential to mention that keeping the wood submerged in water for a long time reduces the wood’s durability and strength and creates brittleness. As a result, wood should not be submerged in water for long.

2. Artificial seasoning/drying

The process of drying sap from wood in a short time by artificial means is called artificial seasoning. Artificial drying needs for quick utilization of wood. Artificial drying procedures can be done in a variety of ways. E.g.

  • a) Kiln seasoning
  • b) Hot seasoning
  • c) Seasoning by boiling water
  • d) Steam seasoning
  • e) Smoke drying seasoning
  • f) Mc-Needles method of seasoning
  • g) Combined natural and artificial seasoning, etc.
a) Kiln Seasoning of wood

A special type of trolley used for drying wood is called a kiln. This method is called the Kiln seasoning method, as the wood is dried in the kiln. In this method, various devices are connected in a room, and these devices create moisture. It is possible to control the heat and airflow with these devices.

During seasoning, care should be taken to ensure that the wood’s sap does not dry out too quickly. This is because cracks in the wood can occur when the wood dries quickly, and the upper part of the wood will be hard. This method is costly. Ordinary traders can’t do wood seasoning in this way.

There are two types of the kiln. E.g.

  • 1) Compartment Kiln
  • 2) Progressive Kiln

1) Compartment Kiln

The enclosed house or room is called a compartment kiln in which the wood is dried by arranging the wood in a special type of trolley, and this method is called the compartment kiln method. The house or chamber is made up of various devices such as boiler steam pipe, fan heating coil, and control system. It is possible to control the heat, humidity, and airflow inside the room by the devices. It is a costly method. The size of this room is 20′-0 “X8’-0″ X8’-0” for one line trolley. If it is a two-line trolley, then the size will be 20′-0 “X16’-0″ X8’-0”.

Compartment Kiln
Compartment Kiln

Compartment kilns are usually made of steel or brick. The trolleys are mounted on the railway line. They can be easily moved in the compartment by the line. The wood on the trolley is spun vertically and arranged in layers. Three feet intervals maintain at each level of the wood kiln’s strip. In this way, the wood can be stacked up to 6 inches below the ceiling of the chamber or room to ensure that one strip falls on top of the other.

At least 1 foot of space should be left around the room. After arranging the wood in this way, the boiler heats the air in the room through the steam heating coil, and the stream is carried out in all the rooms through the fan when the steam goes out with another line.

In this way, the heated air and moisture enter the wood cell, and the juice inside the cell starts to come out, and the wood dries in the air. There is a stream and wind control system through which the stream and wind can be increased and decreased, and the wood is seasoned smoothly and beautifully.

The kiln is heated to 10,000 Fahrenheit (3600 C) when the wood is inserted into the compartment. Then the temperature is gradually increased to the required amount.

2) Progressive kiln

The shape of the kiln is like a tunnel. It is also called the tunnel kiln. It has doors at both ends. There is a heating coil at one end and a chimney at the other end to get the moisture out. As a result, one end of the coil is hot, and the other end is cold. Arranged small trolleys or carts with wood are gently inserted into the cold end of the tunnel. The dry end of the kiln has a fan arrangement by which hot air flows from the dry end to the inside of the kiln.

This process reduces the moisture of the wood and makes it dry. The process continues until the wood is fully seasoned. When the seasoning is complete, the trolleys are taken out one by one at the hot end. In this tunnel, 8-10 trolleys of wood can be dried. The size of this tunnel is usually 8-12 m long and 1.4-3 m square.

Progressive kiln
Progressive kiln

In this method, 600-700 centigrade temperature will apply for drying wood. 11″-21″ (2.5 cm-5 cm) softwood thick planks or boards 4 to 7 days and three months to 6 months in naturally dry 2.5 cm-5 cm hardwood thick planks or boards can be dried in 8 to 12 days.

This method is more useful, and it is necessary to use this method in all cases where heat-resistant wood cannot be naturally dried to the required extent.

b) Hot Air Seasoning

This method is beneficial for drying small pieces of wood. The pieces of wood are arranged in a closed room. The stream is then converted into warm air using a fan with the required heat through the boiler and flowed into the room. As a result of this warm airflow, the wood cell wall’s moisture is first blown away. As a result, the juice inside the cell gradually dries up. During this practice, the constant temperature inside the room is kept at 1200 Fahrenheit. In this method, all the wood dries evenly.

c) Seasoning by Boiling Process 

In this method, the wood is boiled in boiling water in a large vessel-sized pool called Vet with the open upper end made of steel and the lower end’s heating tube. As a result, the sap inside the wood becomes liquid, and the wood is taken out of the pan and slowly dried in the air. In this way, wood can be dried quickly. The 2.5 cm thick plank can be dried in just 1 hour. This method is quite useful for small pieces of wood. This method reduces the shrinkage of the wood, so the cracks are less. The wood suitable for veneer cutting is dried in this method.

d) Steam Seasoning

In this method, the wood is arranged in a confined room and heated with steam. The amount of pressure varies from 10.8 to 12.3 kg per square centimeter (150-160 pounds per square inch). In this method, the juice of the cells inside the wood comes out with steam. In this way, the wood has to be dried in normal air about 4 to 6 hours after steaming. In this way, wood can be dried quickly, and fungus does not attack and rot. The wood does not shrink too much. As a result, curvature and cracks are less—however, the elasticity and strength of wood decrease.

e) Smoke Drying Process

In this method, the wood is hung, burnt, and dried under the gentle heat and smoke of the fire that is made using rice husk, rice straw, wood powder, etc. Due to the gentle heat and smoking, the sap inside the wood comes out, and the outer surface looks damp. Gradually this moisture evaporates, and the smoking produces a charcoal adhesive on the wood core wall, which sticks to the wood cell wall making the wood more durable. In this method, when skilled hands dry the wood, it becomes more durable. This method reduces the cost of drying wood but is not suitable for large areas.

f) Mc-Needles Process of Seasoning

In this method, the wood should be arranged in an enclosed room in the statuary so that air can circulate it. Then the artificial way is to drive between gentle heat and gas chambers. Gas is produced by burning dried wood powder, rice husk, rice straw, etc. This method is the best among the artificial drying methods.

g) Combined Natural and Artificial Drying 

The wood can be dried properly in a combination of these two methods. First, natural insulation reduces the moisture content of the wood by 25-30%. The rest can then be absorbed through the shuffling method.

Advantages and disadvantages of seasoning

Advantages of Natural Drying
  • In this method, the cost is less.
  • This method has less risk of wood damage.
  • There is no danger of the wood twisting.
  • Cracks in wood are less.
  • There is no danger of wood being bent.
  • There is less risk of wood rot or infection without fungus.
  • Wood is more durable and reliable.
  • All parts of the wood dry evenly.
  • Seasoning does not require much attention.
  • Seasoning can be done in any weather.
Disadvantages of Natural Drying 
  • More time is required.
  • The capital is retained for a more extended period.
  • It is not possible to control the moisture of wood finely.
Advantages of Artificial Drying
  • In a very short time, the wood can be utilized by moistening the desired wood
  • Wood germs are destroyed.
  • Wood cracks and hardness defects are reduced.
  • Insects, spiders, insects can not easily damage the wood.
  • Wood is more robust and more durable.
  • The shrinkage of the wood is less.
  • Large pieces of wood can be refined in less time.
  • Wood can be dried according to the required humidity.
Disadvantages of Artificial Drying
  • It is expensive to season wood in this method.
  • The strength and elasticity of wood decreases.

The amount of moisture in wood for different purposes is given below in percentage rate-

Name of work

  • Exterior work
  • Roof and floor timbers
  • Ordinary internal joint such as furniture

Moisture (%)

  • 16
  • 14
  • 12-14

How to recognize the seasoning wood

  • Seasoning wood is light in weight.
  • If you tap, the wood will make tons of noise.
  • The number of cracks in the wood will be less.

How to recognize the non-seasoning wood

  • The wood will be heavy.
  • The wood will be juicy.
  • When wood is pressed, it will feel soft, and streaks will come out.

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