We get wood from trees. Trees can be found in the forest, farms, gardens, and along the streets. The longer trees are left the bigger and taller they grow. When there are well grown, they are ‘fell’ and taken to the Saw-Mill where they are cut into marketable sizes.
Wood is one of the commonest used materials because it is light, strong and be worked upon easily. Wood is used in making furniture and cabinets. Wood is used in building construction too.
Types of wood
The two main types of wood and their differences are:
|1||This is wood from dicot angiosperm trees.||This is wood from gymnosperm trees.|
|2||They usually have broad leaves.||They have needle-like leaves|
|3||Hardwoods are mostly deciduous.||Softwood trees are coniferous.|
|4||Hardwoods tend to be slower growing.||Softwood trees grow fast.|
|5||Hardwoods tend to be found mixed with a variety of other species.||Softwood usually grows in huge tracts of trees which may spread for miles.|
|6||The seeds of softwood are naked.||The seeds of a hard wood are enclosed.|
|7||Examples include maple, balsa, oak, elm, iroko, opepe, mahogany, and sycamore.||Some examples include pine, redwood, fir, cedar, and larch.|
The major parts of a tree
Root: this holds the tree firmly to the ground. The main function of the root is to hold the tree and absorb water and minerals from the soil.
Trunk or stem: this part acts as a support for the branches, which it raises as high as possible towards the light. It is from the stem or trunk that we get our timber.
The leaves: the leaves are the most important part of a tree. The leaves carry out respiration, photosynthesis and plant transpiration.
Branches are the side shoots that originate from the bud.
Annual Tree Rings record the tree’s age.
The crown is the part of the tree that consists of the leaves and the branches at the top of a tree.
The cambium makes new cells during the growing season that eventually become part of the inner back (Phloem)
The sapwood (Xylem) is the youngest layer of wood that transports water and minerals up to the branches and the leaves.
The inner bark (Phloem) carries nutrients and sugar from leaves down to the tree to its branches, trunk, and roots.
Heartwood is the inner core of dead wood that supports the tree.
CLASS ACTIVITY: describe the following parts of a tree:
The Structure of Wood
Wood is made up of a number of tiny-like units called cells. These cells are called Fibres or Tracheids. They vary in length, but the strength of the wood primarily depends on the thickness of the cell walls
Features of wood
As shown in the diagram above, when a tree is felled the cross-section will show the Pith, the Back or Curtex, the Sapwood, the heartwood, the annual rings, the cambium Layer, and the Medullary Rays
Class Activity: Describe the following parts of the cross section of a tree:
1. The cambium layer:
3. Heart wood:
4. Medullary Rays:
5. The Annual Growth Ring:
6. The Pith:
7. The Bark or Curtex:
Wood Processing:- Wood processing is the process it takes to fell a timber tree in the forest, take it to a sawmill then process it into timber planks. Wood can be fell from two different areas, which are the free area and the forest reserved area. The wood can be transported to the sawmill through Lorries, river or rail.
Wood Conversion is the cutting of splitting of wood into marketable sizes.
Wood Seasoning is the removal of water or moisture content in wood.
Method of wood seasoning:
1. Artificial Seasoning: through the use of ‘kiln’
2. Natural seasoning: through air drying.
Reasons for seasoning wood:
1. It makes the wood more durable
2. It makes the wood lighter in weight
3. It reduces the moisture content
4. It makes the wood more stable
5. It minimizes or prevents attacks from water, bacteria and fungi.
Calculation of the Moisture Content of wood
The moisture content of the timber can be calculated using the formular:
Moisture Content (M.C) = (weight of wet wood – weight of dry wood) x 100
Weight of dry wood
Example: A piece of timber weighed 120kg before drying and 100kg after drying. Find the moisture content of the timber.
Wet Wood = 120kg
Dry Wood = 100kg
M.C. =(weight of wet wood – weight of dry wood) x 100
Weight of dry wood
M.C.= (120 – 100) x 100
M.C. = 20%
1. A piece of timber weighed 88kg before drying and 70kg after drying. Find the moisture content of the timber.
Mention 10 uses of wood.
This is a process of treating wood with chemicals called preservatives to prevent insects’ attack and therefore prolong the service life of the wood.
Methods off Applying Preservatives:
- Injecting under pressure.
- Dipping and stepping.
- Hot and cold open tank treatment.
Types of preservatives:
1. Tar oils
2. Water borne
3. Solvent type
1. What is wood?
2. What is the main source of wood?
3. What are 6 distinctive differences between softwood and hardwood?
4. What are the major parts of a tree?
5. How can the cross section of a tree be drawn and label it correctly?
6. What are the parts of the cross section of a tree?
7. What is wood processing?
8. What is wood conversion?
9. What is wood seasoning?
10. What are the two major types of seasoning?
11. Why is wood seasoning recommendable?
12. How can you calculate the Moisture Content of a piece of timber that weighed 120kg before drying and 100kg after drying?
1. What is metal?
2. What are the three main types of metal?
3. What is Metal Processing?
4. What is a furnace?
5. How can a furnace be described?
Author: Precious Ikpoza