Introduction to Timber Finishes

Once you have finished making a timber product—whether it is a jewelry box or a dining table—you aren't quite done yet! In its raw state, wood is vulnerable. It can absorb moisture, get dirty, or rot. Surface treatments and finishes are the final "coat of armor" and the "makeup" for your project. In this chapter, we will look at how we protect timber and make it look its best using the specific finishes required by the Edexcel syllabus.

Why do we apply finishes?

We apply finishes for two main reasons: Functional (protection) and Aesthetic (looks). Without a finish, most timbers would eventually degrade or lose their beauty.

1. Functional Reasons (Preservation and Protection)

  • Moisture Resistance: Wood is like a sponge. It absorbs water, which can cause it to swell, warp, or even rot. A finish seals the surface.
  • Durability: Finishes help protect the wood from scratches, stains, and daily wear and tear.
  • Preservation: Some finishes prevent insects or fungi from attacking the timber.

2. Aesthetic Reasons (Visual Appeal)

  • Enhancing the Grain: A finish can make the natural patterns in the wood "pop" and look more vibrant.
  • Color: Finishes can change the color of the timber to suit a specific style.
  • Texture: You can choose a finish that feels smooth, glossy, or matte.

Quick Review: Think of a finish like a phone case. It protects the phone from damage (functional) but also makes it look stylish (aesthetic)!

Preparation: The Secret to a Great Finish

Before applying any treatment, the timber must be prepared. If you apply finish to a rough surface, it will look terrible and feel even worse! As we saw in the "Specialist Tools" chapter, we use abrading (sanding) with glass paper to make the surface perfectly smooth. You should always sand in the direction of the grain to avoid scratches.

Prescribed Timber Finishes

For your GCSE exam, you need to know these three specific ways to finish timber products:

1. Varnishing

Varnish is a clear, tough, and protective coating. It is usually made from resin and provides a hard skin over the timber.

  • Characteristics: It is usually waterproof and very hard-wearing. It can be glossy (shiny) or matte (dull).
  • Applications: Used for products that take a lot of abuse, such as coffee tables, wooden flooring, or outdoor furniture.
  • Advantages: Very durable and easy to wipe clean.
  • Disadvantages: It can take a long time to dry, and if it gets scratched, you often have to sand the whole thing down to fix it.

2. Shellac

Shellac is a traditional finish that has been used for centuries. It is actually a natural resin secreted by the female Lac bug, which is then dissolved in alcohol to create a liquid.

  • Characteristics: It creates a high-gloss, deep finish often called "French Polishing." It brings out the warmth of the wood beautifully.
  • Applications: Mostly used for high-end antique furniture or musical instruments (like violins).
  • Advantages: It is natural, dries very quickly, and is easy to "touch up" if it gets damaged.
  • Disadvantages: It is not resistant to heat or chemicals. If you put a hot coffee mug on a shellac-finished table, it will leave a permanent white ring!

3. Veneering

Veneering is slightly different. Instead of a liquid coating, you are applying a very thin layer of high-quality, expensive wood (the veneer) over a cheaper base material, like MDF or Plywood.

  • Characteristics: It makes a manufactured board look like solid, expensive hardwood.
  • Applications: Used in flat-pack furniture, kitchen cabinets, and car dashboards.
  • Advantages: It is much cheaper than using solid hardwood. It is also more stable (less likely to warp) because it is glued to a manufactured board.
  • Disadvantages: The edges can sometimes peel off, and because the layer is so thin, you cannot sand it down very much or you will "sand through" to the cheap wood underneath.

Did you know? A single \(2440 mm \times 1220 mm\) sheet of plywood can be covered in a beautiful Oak veneer, making it look like a solid piece of Oak for a fraction of the price!

Summary Table: Selecting the Right Finish

In the exam, you might be asked to justify why you chose a specific finish. Use this table to help you decide:

Finish Best Used For... Top Benefit
Varnish Kitchen tables, outdoor benches Excellent durability and water resistance.
Shellac Fine furniture, musical instruments Provides a deep, high-gloss traditional shine.
Veneering Wardrobes, desks, office furniture Gives an expensive look for a much lower cost.

Common Mistakes to Avoid

  • Mistake: Forgetting to sand before finishing. Result: The finish will highlight every bump and scratch.
  • Mistake: Using Shellac for a dining table. Result: Hot plates and spilled drinks will ruin the finish immediately.
  • Mistake: Thinking a veneer is a liquid. Correction: Remember, a veneer is a thin layer of wood, not a paint or oil!

Key Takeaways

Functional: Finishes protect wood from moisture and wear.
Aesthetic: Finishes make the wood look better by enhancing the grain or adding color.
Varnish: Tough, plastic-like, water-resistant.
Shellac: Traditional, bug-based, high-gloss, but sensitive to heat.
Veneering: Thin layer of nice wood over cheap wood to save money.