Hello friends, In this article, I am going to tell you about the ” Seasoning of timber” so, I hope you will get full knowledge about it.
Wood:- It is the oldest structural material. It is still almost employed in almost every field of construction. Wood suitable for use of structural material is called timber.
What is seasoning of timber?
As fresh timber which is obtained from trees contains about 30 to 40% sap or moisture. This sap is very harmful to the life of the timber.
Therefore, it is necessary to remove that sap, in other words, the timber is to be dried. This process of drying timber is known as “Seasoning”. That sap is removed by applying some special methods which have described below.
Objective of seasoning of Timber
1. To allow timber to burn readily if used as fuel.
2. To decrease the weight of timber and thereby to lower the cost of handling and transport.
3. To impart hardness, stiffness, strength, and better electrical resistance to timber.
4. To make timber easily workable.
5. To make timber fit for receiving treatment of paints, preservatives, varnishes, etc.
6. To make timber safe from the attack of fungi and insects.
7. To make timber suitable for gluing i.e. effectively joining two members of timber with the aid of glue.
8. To reduce the tendency of timber to crack, shrink and warp.
9. To maintain the size and shape of the components of the timber articles which are expected to remain unchanged in form.
10. To increase the resisting power of timber against decay.
Methods of Seasoning
Seasoning of timber can be carried out by two methods are;
1) Natural seasoning:- It is the oldest method of seasoning. Non technical person can also be done this method.some natural seasoning are;
a) Air seasoning:- This is as yet the most common process of seasoning used through the world. In this process, wood sleepers, planks and scantlings etc cut from the wood logs are stacked in open air.
b) Water seasoning:- In this process log of wood is kept completely immersed in running steam of water, the sap from a cell can be easily washed out, and replaced by water. When such logs are taken out and placed for air seasoning, it takes comparatively less time to become dry.
The timber logs can also be placed in a stagnant water if running water is not available near by in such case, the water should be replaced every week. Placing the logs in water also saves them from unequal shrinkage.
Advantage of natural seasoning are,
- It is highly economical.
- It requires little supervision.
- It is applicable to thicker as well as thinner section.
Disadvantage of natural seasoning are;
- It is very slow process.
- keeps valuable land and timber blocked for larger periods, and hence in some cases may economical.
- Moisture content can’t be below a certain limit (16-17%).
- Seasoning isn’t always uniform in all the section of timber.
2) Artificial seasoning:- Artificial seasoning are the quick process of seasoning and moisture content can be controlled. The popular method of artificial seasoning is kiln seasoning.
a) Kiln seasoning:- In this process timber is seasoned under controlled temperature and humidity condition with proper air circulation and ventilation system. The rise in temperature should be such that the timber retains originals strength and elastic properties.
Humidity controls the warping and cracks of timber. Circulated air causes the uniform drying of timber and ventilation reduces the excessive heat. Due to uniform drying in control way, any moisture content can be obtained from this method.
But timber obtained is of inferior quality than that from natural seasoning. This is quick process but costly. It requires skilled manpower. It takes 4 to 5 days for complete seasoning in normal condition.
b) Chemical seasoning:- In this method, the timber piece to be seasoned is treated with a chemical solution like sodium chloride, sodium nitrate.
In other words, chemical seasoning enables the timber to dry first from inside. It is definitely an advantage as it prevents the risk of cracking of outer cell.
c) Seasoning by boiling:- This is also quickly method of removing sap from with in a cell. The timber is to be seasoned is immersed in water and the water is heated to boiling temperature.
It is kept boiling for 4 to 5 hours. The sap is washed out by this process. On placing in air such treated timber dries quickly.
d) Electrical seasoning:- It is of theoretical use only. Dry wood is not conductor of electricity. But high alternating current is through apiece of green timber, heat generated is enough to dry out the moisture of the cells which do conduct some electricity.
The technique involves costly equipment and even the consumption of electricity is high that the process is uneconomical.
So, friends, I hope this article about ” various types of Seasoning of timber” remains helpful for you.