SEASONING OF WOOD

SEASONING

Seasoning is the controlled process of reducing the moisture content (MC) of the timber so that it is suitable for the environment and intended use. Wood will dry naturally so seasoning helps us to control the process and keep the timber more stable and more useful. Prevents splitting Prevents a lot of fungal and insect attacks It is less lightly to distort or warp later After seasoning timber is easier to work with, because it is lighter, harder and stronger.

Objectives of Seasoning:

Following are the objectives of seasoning of wood

Reduce the shrinkage and warping after placement in structure. Increase strength, durability and workability. Reduce the tendency to split and decay. Make it suitable for painting. Reduce its weight to transport and handle.

TYPES OF SEASONING

Natural Seasoning: When timber is felled, it is removed from the forest and placed in open air to remove the water contents in it. Square timber does not split so much as the round one. When beams are to be used the full size of tree then. It would be good preservative against splitting to bore them from one end to another end.

TYPES OF NATURAL SEASONING

Air seasoning:

Air Seasoning With this process the timber is roughly sawn to size and stacked using spacers called stickers, with the timber stacked in the open air. Vertical spacing achieved by using timber battens

(25mm) of the same species. The piling sticks should be spaced close enough to prevent bowing (600 to 9 00 mm centers) this allows the free movement of air. The stack should be protected from the direct influence of the elements. The ends of the beams must be painted to prevent splitting.

Water seasoning :

A wood treatment process in which lumber is soaked in water prior to air drying. In this method wood is layed down on water about a fortnight then it is taken out to dry in air situation. Now the dry air will remove the moisture content from it.

Artificial Seasoning:

In this method timber is seasoned in a chamber with regulated heat, controlled humidity and proper air circulation. Seasoning can be completed in 4 to 5 days only. The

Different methods of seasoning are:

Chemical Seasoning:

In this method, the timber is immersed in a solution of suitable salt.Then the timber is dried in a kiln. The preliminary treatment by chemical seasoning ensures uniform seasoning of outer and inner parts of

timber.

Electrical Seasoning:

In this method high frequency alternate electric current is passed through timber. Resistance to electric current is low when moisture content in timber is high. As moisture content reduces the resistance reduces. Measure of resistance can be used to stop seasoning at appropriate level.

Kiln Seasoning:

Kiln is an airtight chamber. Timber to be seasoned is placed inside it. Then fully saturated air with a temperature 35°C to 38°C is forced in the kiln. The heat gradually reaches inside timber. Then relative humidity is gradually reduced and temperature is increased, and maintained till desired degree of moisture content is achieved.

The kiln used may be stationary or progressive. In progressive kiln the carriages carrying timber travel from one end of kiln to other end gradually. The hot air is supplied from the discharging end so that temperature increase is gradual from charging end to discharging end. This method is used for seasoning on a larger scale.