Timber Surface Treatments and Finishes
Why timber needs protecting from moisture, decay and insects, and the main finishes used on it: painting, varnishing and tanalising, and the difference between a surface coating and a pressure treatment.
Justify the choices, the way you are assessed
Free interactive practice on the decisions the assessment actually asks you to justify.
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Why timber needs a finish
Bare timber left outside soaks up water, rots and is attacked by insects, and even indoors it can look dull and mark easily. A finish protects the surface and improves how it looks. This module covers why timber is treated and the main finishes used on it, including the difference between a coating you brush on and a treatment forced deep into the wood.
Finishing words to know
Learn these before you sort the finishes.
A coating against a treatment
Not every finish works the same way.
Name the finish and its job
In the exam, name the finish and say exactly what it protects against, such as moisture or decay. Then say whether it is a coating brushed onto the surface or a treatment driven deep into the wood. For timber use the words decay and moisture, not corrosion or oxidation, which belong to metals.
Match the finish
- paint
- varnish
- tanalising
- oil
- a coloured coating that hides the grain
- a clear coating that shows the grain
- a preservative forced in under pressure
- soaks in to feed and protect the surface
What is tanalising?
Which statement best describes tanalising?
- A preservative forced deep into the timber under pressure.
- A clear varnish brushed onto the surface.
- Simply making the timber waterproof with wax.
- A coloured paint that hides the grain.
Why finish timber?
Select the TWO main reasons for finishing timber.
- To protect it from moisture and decay
- To improve how it looks
- To make it much heavier
- To make the timber grow
Count the coats left
A varnished tabletop needs 3 coats in total. The maker has applied 1 coat so far. Subtract to find how many coats are still to apply. What is the answer?
Order the finishing job
Put the steps of finishing a piece of timber in order, earliest first.
- Sand the surface smooth
- Wipe off the dust
- Apply the first coat
- Let it dry, then recoat
Complete the facts
Timber is finished to protect it from moisture and _____ and to improve how it looks. _____ is a clear coating that still shows the grain, while paint is a coating that _____ the grain. Tanalising is different because the preservative is forced in under _____.
Match the problem to the fix
- a fence post standing in wet ground
- a wooden table that must show its grain
- an outdoor door that needs a strong colour
- a chopping board that touches food
- tanalising to resist rot underground
- clear varnish to seal and display it
- weatherproof paint for colour and cover
- food-safe oil rubbed into the surface
Spot the surface coatings
Tap the TWO finishes that are brushed onto the surface rather than forced in.
- paint
- varnish
- tanalising
- pressure preservative
Choose the finish
Read each job and choose the best finish.
- A timber fence post will stand in damp soil for years. Which finish suits it best?
- A maker wants an indoor table to keep its natural grain on show but be protected. Which finish suits it best?
- A pupil says tanalising just makes wood waterproof like a coat of wax. Is that correct?
Explain timber finishes
Explain why timber is finished and compare a surface coating with a pressure treatment, using named examples.
- Give two reasons timber is finished
- Describe one surface coating and what it does
- Explain how tanalising is different from a coating