Surface Treatments & Finishes
GCSE — 2.1.2 In-depth Knowledge: Product Design
Why apply a surface finish?
Surface treatments can be applied for:
- Functional reasons — to improve the performance of the material or product (e.g. corrosion protection, water resistance)
- Aesthetic reasons — to improve the visual appearance of the material or product
Metal surface treatments
Before applying any finish, the metal surface must be prepared — dust, grease and rust must be removed. Some finishes need the surface to be keyed (roughened) to grip the finish.
| Finish | Description |
|---|---|
| Powder coating | Dry powder applied then cured in an oven — durable and colourful |
| Galvanising | Coating with zinc to prevent rust |
| Enamelling | Fusing glass powder to the metal surface — decorative and durable |
| Oil and wax finishing | Protective and enhancing finish |
| Primer and paint | Colourful protective coating; primer applied first |
| Electroplating | Depositing a thin layer of metal onto the surface (e.g. chrome plating) |
Surface treatment of timbers
Timber finishes are varied and include both functional and aesthetic applications depending on the location of the product.
| Finish | Description |
|---|---|
| Paint | Colourful and protective; gloss, matt or silk; applied with brush, roller or sprayer |
| Wood stain | Applied to enhance appearance; provides some protection; normally sealed with varnish |
| Oil and wax | Soak into the timber, enhance appearance and repel moisture |
| Varnish | Shiny coat applied in layers for durability; glossy or matt |
| Dip-treating | Protects surface; outdoor timber fences often use pressure-treated timber for longevity |
| Preservative | Long-lasting protection, especially for outdoor wood |
Self-finishing polymers
Self-finishing — some plastics require no further finishing after forming in a mould, as the mould surface dictates the finish on the polymer.
- Vacuum forming allows a flat, glossy sheet to take the shape of the mould — the outcome duplicates the surface of the mould used
- This means no additional finishing is required if the mould surface is smooth
If a polymer has been cut from stock form (e.g. acrylic from a sheet), cut edges will be rough and need to be sanded or flame-polished.
Finishing processes for papers, cards and boards
| Process | Description |
|---|---|
| Die cutting | Stamping the required shape out of a sheet using metal cutters |
| UV varnishing | Specialist high-gloss finish using ultraviolet varnish, e.g. on a business card |
| Embossing | Creates a raised pattern or shape, e.g. in a greeting card or wedding invitation |
| Debossing | Same as embossing but the feature is below the surface |
Folding process
Paper, card or board products must be folded correctly to avoid breaking or tearing:
- A crease is applied so the material bends without breaking
- A perforated line or score ensures the fold happens in exactly the right place
- Examples: greetings cards, menus, invitations, packaging
Binding products
When binding a book or pamphlet, pages must be held securely so they don’t fall out:
- Hand stitching — skilled and time-consuming; fixes pages together permanently
- Comb binding — holes punched in pages; a plastic comb holds pages in order; common and less specialist
- Stapling and split pins — other common binding methods