What is Seasoning of Timber? Various Methods of Seasoning of Timber

Seasoning of timber is defined as the process of drying out water from "wet" or "green" timber. Drying the moisture out of timber or wood enhances its properties in terms of strength and durability. 

The moisture content is timber can be calculated as the ratio of the weight of water contained in a piece of timber compared with the weight of the actual woody substance in the same piece. It is expressed in percentage as:

Moisture Content of Timber = [Weight of Water/ Weight of Wood Substance ] x 100

How Timber Dries

Methods of Seasoning Wood or Timber

The two methods used for seasoning timber are:

1. Natural Seasoning
2. Artificial Seasoning

1. Natural Seasoning of Timber

Natural seasoning employs natural resources like air or water to season the timber. Based on this, there is water seasoning and air seasoning.

1.1. Water Seasoning of Timber

In water seasoning, the timber is immersed in water flow which helps to remove the sap present in the timber. The time period for water seasoning of timber is between 2 to 4 weeks. After this, the timber is allowed to dry and used for construction activities.

Fig.2. Water Seasoning Timber

1.2. Air Seasoning of Timber

Air seasoning or air drying is one of the satisfactory methods used for seasoning. The principle used in air drying is to have as much airflow over the timber to allow it to dry efficiently. In order to provide proper circulation of air and to allow all parts of the material to dry, they are arranged in a stack. The layers of the boards are separated by using small sections of timber called as strips/stickers.

Air Seasoning Timber
Image Credits: Woodcraft Supply

2. Artificial Seasoning of Timber

Artificial seasoning of timber was developed to solve the issue of time consumed by natural seasoning. This method seasons the timber within 4 to 5 days. The different methods of artificial seasoning are:

2.1. Seasoning by Boiling

Seasoning of timber by boiling method is the fastest method in the artificial seasoning of timber. This method provides seasoned timber within 3 to 4 hours. After boiling the timber, it is taken for drying.
When a large quantity of timber is there to season, hot steam is passed through a timber log that is stacked within an enclosed room.
Timber seasoning by boiling method improves the strength and elasticity of the timber material. But it is an expensive method.

2.2. Chemical Seasoning

Chemical seasoning stores the timber in a salt solution for a particular duration of time, The salt absorbs the water from the timber and hence, the moisture from the wood is removed. The timber is then allowed to dry.

2.3. Kiln Seasoning

Kiln seasoning of timber involves allowing hot air to pass through an airtight chamber with timber stacked. The temperature inside the chamber is increased using heating coils. After the required temperature is reached, the moisture content and the relative humidity of the timber reduces and finally gets seasoned. Kiln seasoning is costly but provides quality seasoned timber.

Kiln Seasoning

2.4. Electrical Seasoning

Electrical seasoning of timber involves subjecting timber to high-frequency alternative currents. The resistance of timber against electricity is measured at every internal time. The process stops when the resistance required is reached. This method is rapid but uneconomical.

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