Seasoning of Timber

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Seasoning of Timber

• Grade 8

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Seasoning logs
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What is seasoning of timber

• When a tree is cut down the wood contains a large
  amount of moisture. It would not be wise to use
  the wood in this wet state. The moisture must be
  dried out and the controlled process of doing so
  is called seasoning.

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How does moisture affect timber?

• The water will affect timber in many ways, for
  example
• Strength properties will be reduce
• Fungal attack is over likely
• The timber is vulnerable to some species of wood
  destroying insects
• There excessive weight due to the amount of water
  present
• The surface finish is unsuitable to receive
  either paint or polish
• Adhesives will have minimal holding properties

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Methods of seasoning

• There are two methods of seasoning
• air seasoning, sometimes called natural
  seasoning,
• kiln seasoning.

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Air seasoning

• The easiest way, but not the most effective
  method of seasoning timber, is to stack it
  outside. The timber is laid out as seen in the
  diagram below. It is normally placed in a hut /
  building, with two sides open to allow air to
  circulate. The roof and two other sides keep the
  timber relatively dry. The circulation of the air
  slowly dries the timer. However, this techniques
  does not give a precise moisture content. This is
  because air circulates freely and carries
  moisture, depending on the weather and the time
  of year.The spacing sticks keep the seasoning
  boards a short distance apart. The air flows
  between each of the seasoning boards, allowing
  them to dry slowly. In this way warping is kept
  to a minimum.The seasoning time varies
  depending on the thickness of the wood boards and
  the time of year. Usually three to four months
  for 25mm softwoods. The time is doubled, for wood
  twice as thick. Hardwoods of 25mm thickness
  require about six months and up to at least a
  year for 50mm boards.

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Air seasoning
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Air Seasoning- Advantages

• Advantages of Air Seasoning
• No expensive equipment needed
• Small labour cost once stack is made
• Environmental friendly-uses little energy

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Air Seasoning- Disadvantages

• Disadvantage of Air Seasoning
• It takes much longer than kiln seasoning
• Large area of space reqired for a lot of wood
• it is notable to produce timber not dry enough
  for use in the dry, centrally heated air of
  modern buildings

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Kiln Seasoning

• In this method the wooden pieces are kept on huge
  trolleys and then it is placed inside the hot
  chamber of a furnace known as kiln. In this way
  wooden pieces are kept in a controlled
  atmospheric conditions for two weeks. The time
  depends upon the type of wood and initial
  moisture content. Blowers are also used. It is a
  quick drying method and the moisture is reduced
  to 10. Since seasoning is done at a lesser time
  through artificial means so the quality of wood
  is inferior in comparison to seasoned wood
  through natural seasoning.

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Kiln Seasoning
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Kiln seasoning
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Kiln seasoning

• Advantages of Kiln Seasoning
• It is dries quickly
• It can be controlled
• Achieve a lower moisture content
• Defects associated with drying can be controlled

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Kiln seasoning

• Disadvantage of Kiln Seasoning
• It is an expensive method
• Requires supervision by a skilled operator
• Uses a lot of energy

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summary