Back to: BASIC TECHNOLOGY JSS3
Welcome to class!
In today’s class, we will be talking about Wood. Enjoy the class!
Introduction to Wood Processing
Wood is obtained from trees that grow around us. It serves as a raw material in producing wood products.
It is important to note that wood cannot be used to produce the materials needed domestically and industrially if it does not pass through the necessary stages of being processed.
NOTE: Wood that is suitable for engineering work is called timber.
What is Timber?
Timber can be defined as a piece of wood used for various domestic and industrial woodwork. Trees that provide timber are usually trees with a big trunk. These trees grow fast in the southern region of Nigerian because of the heavy rains and the long period of rain in the region annually.
Qualities of a good timber
- The fibres of a quality timber should be straight.
- Its colours should be uniform. E.g. a dark colour indicates strength and durability.
- A quality timber should smell sweet.
- A good timber must be free from any of the defects either natural or artificial defects.
Processing of wood production
Wood processing is done in the following ways:
- Wood conversion
- Felling of trees
- Wood seasoning
- Wood preservation
Felling of trees:
This is the act of cutting down trees in the forest. Felling of trees is done with the aid of chain saw. The tree is then cut into pieces of different required lengths and sizes. The branches are cut and arranged neatly, rather than trying to move the whole trunk in one piece.
This is the process of applying chemicals on wood to prevent insect and fungi attack. Wood is usually attacked by insects and fungi. They probably attack wood because of the starch and glucose in it.
Preservatives help to protect wood against termite, insect and fungi attack.
NB: The chemicals used to prevent the insects and fungi from affecting the wood is called preservatives.
Examples of preservatives for wood are creosote and chlorinated phenols.
Types of wood preservatives
- Water-soluble preservatives: These are the chemicals that can be mixed thoroughly with water only.
- Tar oils: The distillation of coal tar with kerosene gives birth to a blackish-yellow solution called creosote. It smells like carbolic acid. It is used on wood surfaces to protect it against insects and fungi.
- Solvent preservatives: These are the chemicals that can be mixed thoroughly with evaporating liquids only.
- Borate preservative: Boric acid, oxides and salts (borates) are effective wood preservatives and are supplied under numerous brand names throughout the world.
- Potassium silicate-based preservatives: They are a surface application with a minimal impregnation for inter use.
Methods of applying the preservatives
- Painting: This method involves the brushing of the preservative on the surface of the wood. Penetration is very minimal using this method.
- Cold immersion method: This method is slightly different because in this case the solution is not heated. The wood can be fully immersed or only the butt ends.
- Pressure treatment method: This is the process in which the plank is placed inside an enclosed metal cylinder. In this process, the preservatives are being forced into the plank under high pressure.
- Spraying method: This is the use of a spraying machine to apply preservatives in the form of pigments of stable metallic oxides in paints to the wood surface.
- Open tank method: This method involves an open tank or drum containing the heated preservative to a high temperature of 2000 F and the wood soaked into it.
Properties of good timber preservative
- Safe to handle.
- It must be easy to apply to wood.
- It must not have a damaging effect on the timber.
In our next class, we will be talking about PROCESSING OF WOOD – Wood conversion. We hope you enjoyed the class.
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What about growth of trees
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