Processing of Wood: Manufactured Board

Subject: Basic Technology
Class: JSS 3
Term: First Term
Week: 4
Age: 12-15 years
Topic: Processing of Wood
Sub-topic: Manufactured Board – Defects and Preservation
Duration: 60 minutes

Behavioural Objectives

By the end of the lesson, students should be able to:

1. Define manufactured boards and describe their types.
2. Identify common defects in wood and manufactured boards.
3. Explain the importance of wood preservation.
4. List and describe common wood preservatives.

Keywords

• Manufactured Board
• Defects
• Preservation
• Warping
• Preservatives

Set Induction

Start by displaying different types of manufactured boards such as plywood, chipboard, and MDF (Medium-Density Fibreboard). Engage students by asking if they’ve seen or used these materials before, and in what situations.

Entry Behaviour

Students should already have knowledge of basic wood processing and seasoning from the previous lesson.

Learning Resources and Materials

• Samples of plywood, MDF, and chipboard
• Whiteboard and markers
• Handouts showing types of defects in wood
• Videos on wood preservation techniques

Building Background/Connection to Prior Knowledge

Link the discussion to the previous lesson on wood processing, emphasizing the need for preserving wood and identifying defects to ensure durability.

Embedded Core Skills

• Observation and identification skills
• Problem-solving and critical thinking
• Communication skills

Learning Materials

• Samples of preserved and defective boards
• Infographics on wood preservatives
• Videos demonstrating wood treatment

Reference Books

• Lagos State Scheme of Work
• Basic Technology for Junior Secondary Schools
• Wood Science and Preservation Guide

Instructional Materials

• Printed diagrams showing common wood defects
• Preservative samples (e.g., varnish, creosote)

Content

I. Manufactured Boards

Manufactured boards are man-made wood products made by bonding wood fibers, veneers, or particles with adhesives. They are often used in place of solid wood.

1. Types of Manufactured Boards:
   • Plywood: Thin layers of wood veneers glued together.
   • MDF (Medium-Density Fibreboard): Made from compressed wood fibers.
   • Chipboard: Compressed wood chips bonded with resin.
   • Blockboard: Strips of wood sandwiched between veneers.
   • Hardboard: A dense board made from wood fibers under high pressure.
2. Advantages of Manufactured Boards:
   • They are more affordable than solid wood.
   • They are more resistant to warping.
   • Manufactured boards are available in larger sizes.

II. Defects in Wood and Manufactured Boards

1. Definition:
   Wood defects are flaws that affect the appearance, strength, or usability of wood and boards.
2. Types of Defects:
   • Warping: A distortion in the shape of the wood (e.g., bowing, twisting).
   • Cracking and Splitting: Separation of wood fibers due to drying.
   • Knots: Dark circular spots where branches once grew.
   • Decay and Rot: Caused by fungi or moisture exposure.
   • Insect Damage: Holes or tunnels caused by termites and beetles.

III. Wood Preservation

1. Definition:
   Wood preservation involves treating wood with chemicals or natural methods to protect it from decay, insects, and environmental damage.
2. Importance of Wood Preservation:
   • Prevents insect infestation and fungal growth.
   • Increases the lifespan of wood products.
   • Maintains the structural integrity of wood.
   • Reduces maintenance costs.
3. Methods of Wood Preservation:
   • Chemical Treatments: Applying preservatives like varnish, creosote, or paints.
   • Pressure Treatment: Injecting chemicals into wood under high pressure for deep protection.
   • Oiling: Using natural oils like linseed oil to protect outdoor wood.
   • Painting or Staining: Coating wood surfaces to protect against moisture.

Evaluation (Fill-in-the-Blank Questions)

1. __________ boards are made from bonding wood veneers together. (a) MDF (b) Plywood (c) Blockboard (d) Hardboard
2. One common defect in wood is __________. (a) sanding (b) warping (c) painting (d) knotting
3. __________ is a preservative used to protect wood from insects. (a) Oil (b) Creosote (c) Water (d) Dust
4. __________ is a dense board made from compressed wood fibers. (a) Chipboard (b) Hardboard (c) MDF (d) Plywood
5. __________ involves injecting chemicals into wood under pressure. (a) Air drying (b) Painting (c) Pressure treatment (d) Oiling
6. Warping refers to __________ in the shape of wood. (a) growth (b) distortion (c) decay (d) strength
7. __________ is caused by fungi in wood. (a) Rot (b) Knot (c) Warp (d) Twist
8. __________ boards are made from wood chips bonded with resin. (a) Blockboard (b) Chipboard (c) MDF (d) Hardboard
9. The process of treating wood to increase its lifespan is called __________. (a) conversion (b) preservation (c) drying (d) milling
10. __________ oil is used to protect outdoor wood. (a) Sunflower (b) Linseed (c) Corn (d) Castor
11. Defects in wood reduce its __________. (a) color (b) strength (c) price (d) availability
12. Insects such as __________ can damage wood by creating tunnels. (a) ants (b) beetles (c) flies (d) bees
13. __________ is a natural method of preserving wood. (a) Painting (b) Sanding (c) Oiling (d) Pressure treatment
14. A defect known as __________ appears as a circular spot where a branch once grew. (a) decay (b) knot (c) twist (d) warp
15. Wood that is __________ treated is more resistant to weather conditions. (a) chemically (b) poorly (c) naturally (d) lightly

Class Activity Discussion (FAQs)

1. What are manufactured boards?
   Manufactured boards are man-made wood products made from wood fibers or particles bonded together.
2. What is plywood used for?
   Plywood is used for furniture, construction, and interior paneling.
3. What causes wood to warp?
   Warping occurs when wood absorbs or loses moisture unevenly.
4. How can wood defects be prevented?
   Proper seasoning and preservation help prevent defects.
5. What is creosote used for?
   Creosote is used to protect wood from insects and fungi.
6. How does pressure treatment work?
   Chemicals are injected into the wood under high pressure to ensure deep protection.
7. What is the difference between MDF and chipboard?
   MDF is made from fine wood fibers, while chipboard is made from larger wood chips.
8. Why is oiling important for wood?
   Oiling protects wood from moisture and enhances its appearance.
9. What happens to untreated wood?
   Untreated wood is more prone to decay, insect attacks, and warping.
10. How does painting preserve wood?
    Painting creates a barrier that protects wood from moisture.

Teacher’s Activities

1. Introduce the topic by showing samples of manufactured boards and discussing their uses.
2. Lead discussions on common defects and ways to preserve wood.
3. Provide handouts and demonstrate simple preservation techniques like oiling and painting.

Learners’ Activities

1. Identify different types of manufactured boards from samples provided.
2. Discuss common wood defects and their causes.
3. Participate in a group activity to list ways to preserve wood.

Evaluation Questions

1. What are manufactured boards?
2. List three types of manufactured boards.
3. Explain what causes wood to warp.
4. Describe two methods of wood preservation.
5. What is pressure treatment?
6. How does oiling protect wood?
7. What are the advantages of using MDF over solid wood?
8. Why is it important to treat wood?
9. What is the role of creosote in wood preservation?
10. How can painting help protect wood?

Conclusion

The teacher will assess students’ responses and provide feedback, clarifying any misconceptions about defects and preservation in manufactured boards.