Seasoning Seasoning is the reduction of the moisture content of wood. Seasoning is also the controlled drying out of timber. About 50% of the weight of newly-felled tree is water

Seasoning Reasons for Seasoning: Seasoning helps to save the wood from splitting. Dry timber (< 20% MC) will not be attacked by fungi Dry timber is less likely to be affected by shrinkage or distortion After seasoning, timber will be lighter, harder and stronger. Seasoning produces timber that is easier to work with.

Seasoning 13% - (Australia)

Relative Humidity “The amount of moisture in the air at a given temperature, compared with the maximum amount of moisture the air could hold at that same temperature”. There is a certain amount of water vapour in the air at all times, depending on the weather, season, etc.

Moisture Content “The amount of moisture present in the wood is shown as a percentage (%) of the weight of the wood when dry” Wood is hydroscopic so moisture changes will affect it so it will soak up or let out moisture until it has reached a balance = Equilibrium Moisture Content (EMC).

Natural Seasoning Also known as Air Seasoning. Planks of green timber are laid down on battens and have a gap between them to allow air to circulate. Stickers or skids are the small pieces of wood that allow the air travel between the planks.

Natural Seasoning The stack should be: -Covered to prevent rain damage while the planks dry out. -On a clean dry site -All planks of the same species and similar sizes should be kept in the one stack -The ends of the boards should be protected from the sun to prevent excessive drying-out.

Natural Seasoning Advantages of Natural Seasoning -No expensive equipment required -Small labour cost once the stack is made -Not wasteful of energy Disadvantages of Natural Seasoning -Slow drying rate -Large area of space required -Dependant on the weather -Rate of seasoning cannot be carefully controlled -Only seasons to a MC of 18% - 22%

Kiln Seasoning The lumber is placed in large kilns (ovens) where temperatures, humidity and drying rates are controlled There are 2 types of kiln: -Compartment Kiln & Progressive Kiln

Compartment Kiln Timber is stacked similar to that in natural seasoning only it is on a trolley which runs on rails. The kiln is closed before steam jets in the walls, ceiling and floor release heated steam. The timber is allowed to heat up but not dry out.

Compartment Kiln The relative humidity of the kiln is reduced (controlled)while the heat is maintained. (This allows moisture in the wood to evaporate gradually) Fans circulate the air around the kiln. Air vents allow moist wet air out and fresh air in.

Progressive Kiln The progressive kiln is a continuous kiln. The timber goes through the various stages of drying as it moves through the kiln on a trolley. The drying process is the same as that for the Compartment Kiln.

Kiln Seasoning Advantages of Kiln Seasoning -Quicker due to higher temperatures, ventilation and air circulation -Achieves a lower moisture content -Provides greater degree of control during the drying process -Allows more precise rates of drying -Allows uniform circulation through the stack -Control over moisture content and rate of drying can be achieved -Artificial defects can be controlled Disadvantages of Kiln Seasoning -It is expensive -Requires supervision by a skilled operator -Is dependant on energy