SEASONING OF TIMBER

SEASONING OF TIMBER

       Removal of moisture from timber so as to be in equilibrium with moisture in surrounding atmospheric conditions, where timber is likely to be used is called as seasoning of Timber.

SEASONING METHOD

           Seasoning are two types

• Natural Seasoning
• Artificial Seasoning

Natural Seasoning

  They are two types

• Air Seasoning
• Water Seasoning

Air seasoning

      Air seasoning is best method of seasoning. In this method, water or the moisture is driven out from the timber by a very slow process out from the timber by a very slow process of evaporation. The object of seasoning is to ensure regular and uniform drying throughout the timber. In this process, the timber balks are stacked under a shed. The timber balks should be kept perfectly horizontal, to avoid twisting of timber during seasoning. The stack should be made on damp proof materials, perferably on cast iron, stones, concrete block etc. The stacks should be kept up from ground at least by 30 cm as shown finger.

Water Seasoning

   Water seasoning method, the logs are kept immersed in ponds or in running steams with the root ends upstream for three to four weeks. Maximum sap is washed out by this process. the logs should be kept entirely down under water by chaining them. Now after that these logs are kept under shed for free air circulation.

Artificial Seasoning

• Hot air seasoning
• Mc Nellis seasoning
• Seasoning by Boiling in Water
• Seasoning by Steaming

Hot Air Seasoning

        Hot air seasoning process, the timber are stacked in racks in a hot chamber heated with steam pipes on the floor. Within the hot chamber the timbers are subjects to a swifty moving current of air passing over the hot  pipes. The timber are kept there for about three days at a constant temperature of 90*C. The hot air absorbs sap or moisture content of the timbers. 

              The moisture-laden air is expelled from the upper part of the chamber and fresh dry air is introduced from the bottom. the process is also known as kiln-seasoning. It renders timber brittle and bleaches deep coloured timber.

  Mc Neills Seasoning

   This is believed to be the best process of artificial seasoning, as it has no adverse effect on the appearance and strength of timber. Timber seasoned by this method is rendered harder, denser and proof against dry rot. But, it is a costly method of seasoning timber. The time required varies with the nature of the timber, usually form 15 days to two months. In this process, the timbers are stacked in chamber with one-third air space and containing a large water surface to produce vapour by various hot gases as the products of combustion of fuel in the fireplace withing the chamber. thus, the timbers are subjected to moist warm atmosphere. The chamber is usually built with bricks. the greener the timber when first put into the chamber, better is the result of seasoning. 

Seasoning By Boiling In Water

         Water- seasoning can be hastended by using boiling water. The timber is kept immersed in boiling water for four hours. BY this process the strength and elasticity of the timber is reduced, althougth there is shrinkage. following the boiling, the timber should be dried slowly under a shed. This method of seasoning is expensive. 

Seasoning By Steaming

         This is similar to seasoning by boiling, but the timber dries soon after the steaming. Steaming prevents dry rot in timber, but it is expensive.