Wood finishes.
The use of finishes · Technical principles
Revision notes
Wood Finishing
Natural Wood Degradation
Wet rot: Alternating wetness and dryness means moisture is absorbed into the wood. Even if the surface dries, moisture remains below the surface, breaking down wood fibres. A fungus spreads, making the wood soft, wet, and crumbly.
Dry rot: A different, fast-spreading fungus that turns wood into a dry, soft, powdery state.
Insect attack: Furniture beetles (woodworm) attack softwood and hardwood; deathwatch beetles attack hardwood. Larvae eat into the wood creating tunnels and exit via "flight holes."
Methods of Wood Finishing
Wood Finish | Method of Application | How they enhance appearance or prevent decay |
|---|---|---|
Polyurethane / Acrylic varnish | Available in gloss, satin and matt, clear or colours. Apply a thin coat with a brush in the direction of the grain. Several coats can be applied, rubbing down with fine glass paper between coats. | Provides a hard, tough, heatproof, waterproof finish. Clear finish allows the grain to be seen. |
Water-based paints | Available in gloss, satin, matt and metallic. Applied with brush, roller or spray. Knots should be treated with knotting solution. Surface should be primed and undercoated first. | Provides protection and colour. Used predominantly for softwoods. Makes surfaces more aesthetically pleasing, tougher, and resistant to moisture. |
Stains | Available in many colours. Applied with brush, roller or spray. Surfaces must be grease-free. | Help colour and enhance the grain. Can make inexpensive wood look more expensive. Do not have specific protective properties. |
Colour wash (A-level only) | Available in many colours. Applied with a wet sponge. | Used to colour the wood for a "vintage" style while allowing the grain to show. |
Wax | Available in clear and coloured waxes. Applied with a brush or cloth; once dry, buffed with a lint-free cloth. | Can be buffed to a high-gloss. Increases surface hardness and toughness. Clear finish shows the grain. |
Yacht varnish | Available in high gloss and satin. Applied with a brush or sprayed directly onto the wood. | Suitable for woods that are outside all year (doors, window frames, boat parts). Increases toughness and weather resistance. |
Danish oil (A-level only) | Applied with a lint-free cloth in the direction of the grain. Leave for 5 mins, then rub away excess. Sand/wire wool between coats. | Maintains natural appearance; soaks into the wood. Not hardwearing, but regular coats build a water-resistant finish. |
Teak oil | Applied with a lint-free cloth. Leave for 5 mins, then rub away excess. Used for naturally oily woods. | Primarily for outdoor products to improve weather resistance and resistance to fungal/insect attack. Enhances grain. |
Pressure treating | Wood is placed in a pressure vessel with copper sulphate and preserving salts. Vacuum and pressure force it deep into fibres. | Protects wood for up to 50 years from rot, insects, and weathering. Used for decking, bridge construction, and cable poles. |
Think you have got this topic?
Test yourself before moving on, or use flashcards for a quick recall session.