What are the benefits of kiln drying?

• Dimensional stability and less risk of distortion
• Fungi and moulds cannot survive on dry timber
• Improved penetration of preservatives
• Smoother finish after machining
• Improved performance of finishes such as paints and stains
• Improved insulation
• Improved strength
• Lighter weight

The presence of water in wood

Under ordinary conditions, all wood contains some water, and the amount of water contained in wood at a particular time is known as its moisture content.

The moisture content (MC) of a piece of timber is the weight of water contained in that timber expressed as a percentage of its own weight.

MC % = (Weight of water/Oven dry weight) x 100

MC can be more than 100% and frequently is. Freshly cut plantation grown pine may consist of something like one and a half-parts water to one of wood substance. MC in this case would be 150%.

Green-off-saw timber from hardwood saplings may have a moisture content of about 100%. While the moisture content of mature hardwoods may be in the region of 50%.

Water is the conductive fluid of the living tree. It takes minerals from the soil to the leaves where they are used in the production of sugars and starches - the food of growing trees.
This watery solution is known as sap, a term which is sometimes confused with resinous exudations. However, sap is actually water containing a comparatively small amount of dissolved material, mainly salts. These mineral salts are conducted up to the leaves via the sapwood, and the sugars and starches move in solution through the inner bark back to the roots, nourishing the living cells on the way.

The heartwood, or zone of non-living wood cells, also contains a considerable amount of sap, but no appreciable movement of this sap takes place in the heartwood zone.

Why Season Timber?

In most cases the moisture content of timber in service is in the vicinity of 10-15%. This is a long way removed from the green-off-saw moisture condition mentioned above and, obviously, a considerable amount of drying has taken place.

Whenever timber dries, it shrinks, and seasoning is undertaken mainly to "pre-shrink" timber. This prevents unacceptable changes in size occurring after installation. water from timber so that the amount of water in the timber is in balance with the moisture in the atmosphere.

Timber seasoning is defined as "drying timber to a moisture content suited to the condition and purpose of use".

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