MATERIALS FOR PRODUCTION — WOOD

Pre-technical — Subtopic: WOOD (Age: 14, Kenya)

These notes introduce wood: what it is, common local types, useful properties, how it is prepared and used in production (carpentry, furniture, buildings). Simple pictures and tests are included so you can try them in the workshop or class.

Learning outcomes

• Define wood and know where it comes from.
• Recognise softwoods and hardwoods and some Kenyan species.
• Describe important properties of wood and simple tests for them.
• Know how to season and protect wood and common defects to watch for.
• Know typical uses and safe working tips in the workshop.

1. What is wood?

Wood is the hard, fibrous part of a tree trunk and branches used as a building and production material. It is made of cells that grow in rings (growth rings) and fibres that give strength along the grain.

2. Types of wood (simple)

Softwoods — from cone-bearing trees (evergreens). They grow faster and are usually lighter and easier to work with. Common in Kenya: pine (Pinus) from plantations. Often used for construction framing, sawn timber, and cheap furniture.

Hardwoods — from broad-leaved trees. They are usually denser and harder. Kenyan examples include: mukau, mvule, and some mahogany species; eucalyptus is often used too (can behave like either). Hardwoods are used for strong furniture, doors and flooring.

3. Important properties and quick classroom tests

• Density / weight — heavy = usually harder and stronger. Test: lift two planks of same size; which feels heavier?
• Grain and straightness — straight grain is easier to cut and join. Look along the plank to see fibre direction.
• Hardness — a scratch test with a coin or nail: soft woods dent more easily.
• Moisture content — green (wet) wood is heavier and shrinks as it dries. Simple test: measure weight before and after air drying for a few weeks.
• Workability — how easily wood can be sawed, planed, chiselled or glued.

4. Seasoning (drying) wood

Freshly cut wood (green wood) contains a lot of water. Seasoning removes moisture so wood becomes stable and less likely to warp, crack or rot.

• Air drying — stack planks with spacers (stickers) in a dry, shaded place for several weeks or months. This is cheap and common in Kenya.
• Kiln drying — faster and controlled drying in a heated chamber (used in factories).

Tip: measure thickness before and after drying. Good workshop standard moisture content depends on use (indoor furniture ~8–12%).

5. Common defects and causes

• Knots — where branches were; weak and difficult to work.
• Warping (bow, crook, twist) — caused by uneven drying or growth stresses.
• Checks and splits — surface cracks from rapid drying or shocks.
• Rot and insect attack — caused by moisture and poor storage (termites, borers).

6. Preservation and protection

• Keep wood dry and raised from ground.
• Apply sealants, paint, varnish or oils to keep water out.
• Treated timber (pressure treated) resists insects and rot — used for outdoor work.
• Use borate treatments for protection against insects (follow safety rules).

7. Uses in production (what we make with wood)

• Furniture (tables, chairs, beds).
• Doors, window frames, and flooring.
• General carpentry and joinery (shelves, cupboards).
• Construction (roof trusses, formwork) — mainly softwood in Kenya.
• Crafts and musical instruments (small specialised hardwoods).

8. Tools & safe working

Common hand tools: saw, hammer, chisels, plane, try square, marking gauge. Common power tools (supervised): circular saw, drill, sander.

• Always wear eye protection, dust mask and hearing protection where needed.
• Keep fingers away from blades. Use push sticks with power saws.
• Clamp work securely before cutting or drilling.
• Store wood flat to avoid warping.

9. Simple class activity

Compare two small boards (one softwood, one hardwood):

1. Weigh each board, measure length × width × thickness and estimate density (weight ÷ volume).
2. Try to make a scratch with a nail: which dents more?
3. Leave one piece in shade and one in sun for a week — note any change (warping or cracking).

10. Short glossary

Grain

Direction of the wood fibres.

Seasoning

Drying wood to a stable moisture level.

Knots

Hard, circular parts where branches joined the trunk.

Prepared for Pre-technical learners (age 14) — safe workshop practice and simple experiments will help you understand the behaviour of different woods used in Kenyan production and carpentry.