Seasoning of Timber – Methods of timber seasoning

Seasoning of timber or simply Timber seasoning is the process of drying timber or removing moisture or sap, present in a freshly felled timber, under more or less controlled conditions

Reasons for Timber Seasoning

  1. Freshly felled timber contains moisture 100 to 200% of its dry weight.
  2. A well-seasoned timber contains moisture about 10-12% of its dry weight.
  3. Seasoning should be the first step for the efficient utilization of timber.
    Objective and Advantage
  4. To minimize the tendency of timber to shrink, warp and split.
  5. To increase strength and to make timber more stable.
  6. To make timber safe from the attack of fungi and insects.
  7. To reduce the weight for transport purposes and handling.
  8. To improve the working qualities of timber.
  9. To avoids the defects in timber.
  10. To make it durable.

Method of Timber Seasoning

There are two methods for seasoning of timber.

1. Natural Seasoning of Timber

By natural process, the timber is seasoned. As compared to the artificial seasoning method, this method is time-consuming.

A. Air Seasoning

Sawn timber is stacked in a dry place about 30cm above floor level with longitudinal and cross pieces arranged one upon another, leaving space for the free circulation of air. A pitched roof covering is used to protect from direct sunlight.

Advantages Of Air Seasoning

  • Simple, easy and cheap
  • Less chance of damage.

Disadvantages Of Air Seasoning

  • The process is very slow (takes about 2 to 4 years.)
  • Large space is required.
  • It blocks the capital for a quite long period.
  • It is difficult to reduce the moisture content at our desired job.
  • Timber may get attacked by insects and fungi during the seasoning period.

B. Water Seasoning

Logs of wood are completely immersed in a running stream of water. By this process, the sap, sugar, and gum, etc. are leached out of the wood and replaced by the water. The logs and then taken out and left to dry in an open place.

Advantage Of Water Seasoning

  • It is quick to process than natural air seasoning
  • All the organic food materials present in the sapwood are washed off; the wood is less liable to be eaten away by a worm or to decay by dry rot.

Disadvantage Of Water Seasoning

  • This process reduces the elasticity and durability of the timber.
  • The timber becomes brittle.

2. Artificial Seasoning of Timber

Artificial Seasoning of timber are:

A. Kiln Seasoning

Timber is seasoned under controlled temperature and humidity conditions with proper air circulation and ventilation system. The moisture content of timber should be kept between 10 to 12 % of its dry weight.

Advantages Of Kiln Seasoning

  • Moisture content can be reduced as per requirements.
  • Well seasoned in a short span of time.
  • Less liable to shrinkage and no chance for the attack by insects and fungi.
  • Immediately used when required.

Disadvantages Of Kiln Seasoning

  • Costly and requires skilled labour.

B. Chemical Seasoning (Salt Seasoning)

Timber is immersed in a solution of salt. It is then taken out and then seasoned in an ordinary way. The interior surface of timber dries in advance of exterior one and chances of formation of external cracks are reduced.

C. Electrical Seasoning

This method works on the principle that Heat is produced when poor conductors are placed in the field of high frequency. The wooden plants are made to pass through an induction coil producing field of high frequency.

Due to the electrical induction effect, the moisture content in timber gets evaporated in a uniform way, which results in the superior quality of timber. This is an expensive process which is used to manufacture process of the plywood.

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