SeasoningSeasoning

SeasoningSeasoning is the is the reductionreduction of the of the moisture contentmoisture content of of wood.wood.

Seasoning Seasoning is also is also the controlled the controlled drying out of drying out of timber.timber.

About 50% of the About 50% of the weight of newly-weight of newly-felled tree is water felled tree is water

SeasoningSeasoning Reasons for Seasoning:Reasons for Seasoning: Seasoning helps to save the wood from Seasoning helps to save the wood from

splitting. splitting. Dry timber Dry timber (< 20% MC)(< 20% MC) will not be will not be

attacked by fungi attacked by fungi Dry timber is less likely to be affected by Dry timber is less likely to be affected by

shrinkage or distortion shrinkage or distortion After seasoning, timber will be lighter, After seasoning, timber will be lighter,

harder and stronger. harder and stronger. Seasoning produces timber that is easier Seasoning produces timber that is easier

to work with. to work with.

SeasoningSeasoning

13% - (Australia)

Relative HumidityRelative Humidity ““The amount of The amount of

moisture in the air at a moisture in the air at a given temperature, given temperature, compared with the compared with the maximum amount of maximum amount of moisture the air could moisture the air could hold at that same hold at that same temperature”.temperature”.

There is a certain There is a certain amount of water amount of water vapour in the air at all vapour in the air at all times, depending on times, depending on the weather, season, the weather, season, etc. etc.

Moisture ContentMoisture Content

““The amount of moisture The amount of moisture present in the wood is present in the wood is shown as a percentage shown as a percentage (%) of the weight of the (%) of the weight of the wood when dry”wood when dry”

Wood is hydroscopic so Wood is hydroscopic so moisture changes will moisture changes will affect it so it will soak up affect it so it will soak up or let out moisture until it or let out moisture until it has reached a balance = has reached a balance = Equilibrium Moisture Equilibrium Moisture Content (EMC)Content (EMC)..

Natural SeasoningNatural Seasoning

Also known as Also known as Air Air SeasoningSeasoning. .

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

Natural Seasoning Natural Seasoning The The stack stack should be:should be:

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

Natural SeasoningNatural Seasoning Advantages of Natural Advantages of Natural

SeasoningSeasoning-No expensive equipment -No expensive equipment required required -Small labour cost once the -Small labour cost once the stack is made stack is made -Not wasteful of energy -Not wasteful of energy

Disadvantages of Natural Disadvantages of Natural SeasoningSeasoning-Slow drying rate -Slow drying rate -Large area of space required -Large area of space required -Dependant on the weather -Dependant on the weather -Rate of seasoning cannot be -Rate of seasoning cannot be carefully controlled carefully controlled -Only seasons to a MC of 18% - -Only seasons to a MC of 18% - 22% 22%

Kiln SeasoningKiln Seasoning

The lumber is placed in large kilns (ovens) where The lumber is placed in large kilns (ovens) where temperatures, humidity temperatures, humidity andand drying rates drying rates are are controlled controlled

There are 2 types of kiln:There are 2 types of kiln:

--Compartment Kiln & Progressive KilnCompartment Kiln & Progressive Kiln

Compartment KilnCompartment Kiln

Timber is stacked Timber is stacked similar to that in similar to that in natural seasoning natural seasoning only it is on a trolley only it is on a trolley which runs on rails. which runs on rails.

1.1. The kiln is The kiln is closedclosed before steam jets in before steam jets in the walls, ceiling and the walls, ceiling and floor release heated floor release heated steam.steam.

2.2. The timber is allowed The timber is allowed to to heatheat up but not up but not dry out.dry out.

Compartment KilnCompartment Kiln

3.3. The relative humidity The relative humidity of the kiln is reduced of the kiln is reduced ((controlledcontrolled)while the )while the heat is maintained. heat is maintained. (This allows moisture (This allows moisture in the wood to in the wood to evaporate gradually) evaporate gradually)

4.4. Fans Fans circulatecirculate the air the air around the kiln. around the kiln.

5.5. Air Air ventsvents allow moist allow moist wet air out and fresh wet air out and fresh air in. air in.

Progressive KilnProgressive Kiln

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

Kiln SeasoningKiln Seasoning Advantages of Kiln SeasoningAdvantages of Kiln Seasoning

-Quicker due to higher temperatures, ventilation and air -Quicker due to higher temperatures, ventilation and air circulation circulation -Achieves a lower moisture content -Achieves a lower moisture content -Provides greater degree of control during the drying -Provides greater degree of control during the drying process process -Allows more precise rates of drying -Allows more precise rates of drying -Allows uniform circulation through the stack -Allows uniform circulation through the stack -Control over moisture content and rate of drying can -Control over moisture content and rate of drying can be achieved be achieved -Artificial defects can be controlled -Artificial defects can be controlled

Disadvantages of Kiln SeasoningDisadvantages of Kiln Seasoning-It is expensive -It is expensive -Requires supervision by a skilled operator -Requires supervision by a skilled operator -Is dependant on energy -Is dependant on energy