The use of finishes Paper and board finishing - Metal finishing — AQA A-Level Design and Technology: Product Design
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The use of finishes Paper and board finishing - Metal finishing explained
Sealants are materials applied to a surface or joint to close it against the passage of moisture, air, dust or other substances, and to protect the underlying material.
Read the full explanation
In finishing, a sealant may be applied over a coating or to joints and edges to prevent water ingress and to improve durability. Sealants are chosen for their adhesion, flexibility and resistance to the environment they face; some remain flexible to accommodate movement, while others set harder. Correct application requires a clean, dry surface and full coverage of the joint or area. Learners should recognise the purpose of sealants, where they are used and the properties that make them suitable, distinguishing them from decorative top coats.
Your focus
- Describe the purpose of a sealant in finishing a product.
- Explain how the properties of a sealant suit a particular application.
- Justify the selection of a sealant for a given joint or surface.
The use of finishes Paper and board finishing - Metal finishing exam tips
Marking Points
- Defines a sealant as a material applied to close a surface or joint against moisture, air or dust.
- Explains that sealants protect the underlying material and improve durability.
- Identifies that sealants are applied to joints and edges to prevent water ingress.
- States that sealant choice depends on adhesion, flexibility and environmental resistance.
- Recognises that a clean, dry surface and full coverage are needed for effective sealing.
Examiner Tips
- 💡Link the sealant's purpose to the specific risk, such as water ingress at a joint or edge.
- 💡When justifying a sealant, refer to adhesion, flexibility and environmental resistance.
- 💡Remember that surface preparation (clean and dry) is a condition for effective sealing.
Common Mistakes
- Treating a sealant as purely decorative: a sealant's main role is to close a surface or joint against moisture, air or dust and protect the material.
- Assuming all sealants are rigid: some remain flexible to accommodate movement, so flexibility must be matched to the application.
- Applying sealant to a dirty or damp surface: this prevents adhesion, so the surface must be clean and dry first.