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Wood Working 101

Lesson 2 – Seasoning Timber

Timber Seasoning

After a tree was cut down and/or processed the timber must be seasoned prior to being used. Seasoning timber is the process by which moisture content in the timber is reduced to specific level, typically around 15%.

By reducing moisture content properties of the wood are changed making the wood stronger, increased elasticity, more durable, less prone to rot and decay, lighter, easier to machine with, reduced warping, etc…

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Timber Seasoning

Natural seasoningNatural seasoning is the process in which timber is seasoned by subjecting it to the naturalelements

Artificial seasoningExposing timber to alternative mechanical drying methods.

Natural Seasoning – Water SeasoningWater seasoning is the process in which timber is immersed in water flow which helps to remove the sap present in the timber. It will take 2 to 4 weeks of time and after that the timber is allowed to dry.

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Natural Seasoning – Air SeasoningIn the process of air seasoning timber logs are arranged in layersin a shed. The arrangement is done by maintaining some gapwith the ground. The logs are arranged in such a way that air is circulated freely between logs. By the movement of air, the moisturecontent in timber slowly reduces and seasoning occurs. Even though it is a slow process it will produce well-seasoned timber.

Artificial Seasoning – BoilingSeasoning of timber is also achieved by boiling it in water for 3 to 4hours. After boiling the timber is allowed to dry. For large quantity of timber boiling is difficult so, sometimes hot steam is passed through timber logs in enclosed room.

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Artificial Seasoning – ChemicalTimber is stored in suitable saltsolution for some time. The salt solution used has the tendency to absorb water (diffusion) from the timber. So, the moisture content is removed and then timber is allowed to dry.

Artificial Seasoning – KilnIn this method timber is subjected to hot air in air tight climate controlled chamber. The hot air circulates in between the timber logs and reduces the moisture content. The temperature inside the chamber is raised with the help of heating coils. When the required temperature is obtained moisture content and relative humidity gets reduced and timber gets seasoned.

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Combined SeasoningIt is very common practice to combine natural and artificial seasoning when drying timber. Generally, timber is allowed to natural air dry for a few months, then is placed in a kiln for a few days or weeks to finish the drying process.

Natural vs. Artificial Seasoning

Natural SeasoningAdvantages• Less expensive• Large volumes

Disadvantages• Takes a very long time (months to

years)• No control over the process

Artificial SeasoningAdvantages• Full control the process and better

quality• Very short drying time (days to weeks)• High heat will dry sap, kill fungi,

parasites, bugs, etc…

Disadvantages• Very costly• Difficult to process large volumes

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Equilibrium Moisture ContentAfter wood has been seasoned, the wood needs to stored so it can be acclimatize to its environment. This is done to establish an Equilibrium Moisture Content of the timber…that is to say the moisture content of the timber is the same as the surrounding environemnt.

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