Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 2nd Term
Week: 2
Age: 15 years
Duration: 45 minutes
Subject: Wood Work
Curriculum Theme: Vocational Studies
Previous Lesson: Timber Preservation and Reasons for Preserving Timber.
Topic: COMMON TIMBER PRESERVATIVES AND USES
Subject Matter: types of timber preservatives, application of preservatives, handling preservatives

Specific Objectives

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

Cognitive Domain:

Define timber preservatives.
List common types of timber preservatives.
State different methods of applying timber preservatives.
Mention safety precautions when handling timber preservatives.

Affective Domain:

Appreciate the importance of preserving timber.
Observe safety measures while working with preservatives.

Psychomotor Domain:

Demonstrate the proper application of timber preservatives.
Show correct handling procedures for timber preservatives.

Work cooperatively during practical demonstrations.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Technology (Woodwork Section)
State Unified Scheme of Work for Senior Secondary School Wood Work
Wood Work for Senior Secondary Schools by A.O. Olaitan et al.

Instructional Materials

The teacher will teach this lesson with the aid of:

Samples of timber preservatives (e.g., creosote, wood guard)
Timber samples (treated and untreated)
Gloves
Brush
Safety goggles
Apron

Rationale for the Lesson

This lesson helps pupils understand how to protect wooden structures and items from decay and insect attacks. It enables them to extend the lifespan of timber, which is important for both personal projects and vocational skills development.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of different types of timber and their properties from previous lessons.

Lesson Content/Board Summary

COMMON TIMBER PRESERVATIVES AND USES

Definition of Timber Preservatives

Timber preservatives are chemical substances applied to wood to protect it from decay, fungi, insects (like termites and borers), and marine organisms. They help to extend the service life of timber.

Types of Timber Preservatives

The following are common types of timber preservatives:

Creosote: An oil-based preservative derived from coal tar. It is highly effective against fungi and insects, commonly used for railway sleepers, fence posts, and marine piles. It has a strong odour and dark colour.
Copper Chrome Arsenate (CCA): A water-borne preservative containing copper, chromium, and arsenic compounds. It provides long-lasting protection against fungi, insects, and rot. It is often used for decking, fencing, and structural timber. Timber treated with CCA has a greenish tint.
Boron Compounds: Water-soluble salts that diffuse into the wood. They are effective against insects and fungi but can leach out in wet conditions. Often used for interior timber and as a pre-treatment.
Organic Solvent Preservatives: Contain synthetic pyrethroids or fungicides dissolved in an organic solvent. They penetrate wood easily and do not significantly change its appearance. Used for joinery, windows, and doors.

Methods of Application of Preservatives

The following are common methods for applying timber preservatives:

Brushing: Applying the preservative directly onto the timber surface with a brush. Suitable for small areas or touch-ups.
Spraying: Using a spray gun to apply the preservative. Effective for larger surfaces but requires good ventilation.
Dipping: Submerging timber in a tank of preservative for a short period. Provides better penetration than brushing or spraying.
Pressure Treatment: A commercial process where timber is placed in a sealed cylinder, and preservative is forced into the wood under high pressure. This provides the deepest and most durable protection.

Safety Precautions when Handling Preservatives

It is important to observe the following safety precautions when handling timber preservatives:

Wear appropriate Personal Protective Equipment (PPE) such as gloves, safety goggles, and protective clothing (e.g., apron).
Ensure adequate ventilation in the work area to avoid inhaling fumes.
Avoid direct skin contact with the preservatives.
Do not eat, drink, or smoke while handling preservatives.
Wash hands thoroughly with soap and water after handling preservatives.
Dispose of preservative containers and waste materials according to safety guidelines.
Store preservatives in their original containers, away from children and pets, in a cool, dry place.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them to recall the previous lesson on timber types. The teacher then asks questions like, “What happens to wood if it is left outside in the rain and sun for a long time?” and “How can we make wood last longer?” This leads to the topic of timber preservation.
Pupils’ Activity: Pupils respond to questions and share their ideas about wood durability and protection.
Learning Point: Pupils are prepared for the new lesson and understand its relevance.

Step 2: Definition of Timber Preservatives

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines timber preservatives, explaining their purpose in protecting wood from decay, insects, and fungi. The teacher uses simple language and provides examples of situations where wood needs protection.
Pupils’ Activity: Pupils listen attentively, ask questions for clarity, and take down notes on the definition.
Learning Point: Pupils understand what timber preservatives are and their main function.

Step 3: Types of Timber Preservatives

Time: 10 minutes
Teaching Skill: Listing/Illustration
Teacher’s Activity: The teacher lists and briefly explains common types of timber preservatives such as Creosote, CCA, Boron compounds, and Organic Solvent Preservatives. The teacher shows samples of these preservatives if available and discusses their typical uses.
Pupils’ Activity: Pupils observe the samples, listen to the explanations, and record the different types of preservatives and their uses.
Learning Point: Pupils can identify and differentiate between various timber preservatives.

Step 4: Methods of Application of Preservatives

Time: 7 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher explains and demonstrates (using a small timber sample and a non-toxic liquid if actual preservative is not safe for demonstration) different methods of applying preservatives, such as brushing, spraying, and dipping. The teacher also describes pressure treatment.
Pupils’ Activity: Pupils observe the demonstration, listen to the explanations, and ask questions about the application methods.
Learning Point: Pupils understand how timber preservatives are applied.

Step 5: Safety Precautions when Handling Preservatives

Time: 6 minutes
Teaching Skill: Discussion/Safety Instruction
Teacher’s Activity: The teacher discusses the importance of safety when handling timber preservatives. The teacher lists and explains essential safety precautions, including wearing PPE, ensuring ventilation, and proper disposal. The teacher encourages pupils to share any safety tips they know.
Pupils’ Activity: Pupils participate in the discussion, ask questions, and note down the safety precautions.
Learning Point: Pupils learn and understand the necessary safety measures for handling preservatives.

Step 6: Practical Application (Guided)

Time: 5 minutes
Teaching Skill: Practical Application/Supervision
Teacher’s Activity: If feasible and safe, the teacher guides pupils in a brief, supervised practical activity where they apply a small amount of a safe, non-toxic “preservative” (e.g., water-based wood stain) to a small piece of wood, emphasizing the correct technique and safety measures previously discussed. This reinforces the psychomotor objective.
Pupils’ Activity: Pupils, under strict supervision, practice applying the “preservative” while adhering to safety rules.
Learning Point: Pupils gain practical experience in applying preservatives safely.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define timber preservatives.
List three common types of timber preservatives.
State two methods of applying timber preservatives.
Mention three safety precautions to observe when handling preservatives.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of timber preservation and safety. The teacher assigns homework: “Research other specialized timber preservatives not discussed in class and their specific uses.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their learning and are encouraged to research further.

Lesson Keywords

Preservative – A chemical substance used to protect materials like wood from decay and pests.
Creosote – An oil-based timber preservative derived from coal tar.
CCA (Copper Chrome Arsenate) – A water-borne timber preservative for long-term protection.
Boron Compounds – Water-soluble salts used as timber preservatives, effective against insects and fungi.
Pressure Treatment – An industrial method of forcing preservatives deep into timber under pressure.

Differentiation

For pupils who grasp concepts quickly, the teacher can encourage them to research and present on the environmental impact of certain preservatives or alternative natural preservation methods. For pupils needing more support, the teacher will provide simplified notes, allow peer-assisted learning during practical activities, and give extra individual attention to ensure understanding of definitions and safety rules.

Note for teachers using this lesson plan

Ensure that actual timber preservatives are handled with extreme care and only for demonstration purposes, if at all. Prioritize pupil safety by strictly enforcing the use of PPE and ensuring proper ventilation. If real preservatives are not available or safe for in-class demonstration, use water-based stains or non-toxic liquids to simulate the application process. Emphasize the theoretical knowledge and safety protocols heavily.