This document discusses different wood finishes. It begins by outlining the purposes of applying a finish to wood, which include protecting the wood from wear and tear, preventing decay, and enhancing the wood's appearance. It then describes the two main stages of finishing as surface preparation and application of the finish. A number of specific finishes are discussed such as paint, varnish, Danish oil, wax, and lacquer. Application steps are provided for several of these finishes.

1. WOOD
MATERIALS TECHNOLOGY
4th Edition

2. Chapter 29
Finishes

3. Purpose of a finish
 Protects the wood from wear
and tear
 Prevents decay – fungus, insects
 Provides a nice finished surface
 Enhances colour
 Changes the colour (staining)

4. Finishing stages
Surface
preparation
Application of
finish
 Surface preparation
– Getting the surfaces smooth and
clean
– Preparing the piece before
putting on the finish
 Applying the finish
– The steps in putting on the
different layers of chosen finish
– Different finishes will have
slightly different steps

5. Surface finish
 Rub out/remove pencil lines
 Scratches and marks can be
removed using a scraper
 Punch nails and pin below
surface
 Fill nail holes and small cracks
using a suitable wood filler
 Sand the surfaces smooth using
sandpaper
 Sand end grain
 Start with 100 grit (medium)
sandpaper, then with 180 grit
and finally 320 grit (very fine)
 Always sand with the grain –
avoid scratching the surface
 Brush off all dust or use a tack
cloth

6. Sandpaper (glass paper)
 Composition of sandpaper
– Grit is bonded to the
backing paper or card
– The grit size is printed on
the back of the
sandpaper

7. Types of abrasive

8. Sanding
 Always sand with the grain
 Always sand end grain

9. Paint
 Advantages
–
–
–
–
–
–
Good inside and outside
Lots of colours available
Durable
Long-lasting
Easily-cleaned
Covers scratches and
defects well
 Disadvantages
– Hides the beauty of the
wood
– Difficult to apply well
– Needs good preparation
– Can blister and peel

10. Painting wood
 Prepare surfaces well
 Seal knots with knotting
 Apply primer to all surfaces
 Fill cracks and holes
 Apply 1 – 2 coats of
undercoat
 Sand lightly
 Apply final finish coat
 Allow each coat to dry fully

11. Varnish
 Why choose varnish?
Water-resistant
Scratch-resistant
Easily-cleaned
Clear finish enhances
the grain of the wood
– Resists heat
– Stains/coloured varnish
are available
–
–
–
–

12. Varnish – application
 Apply the varnish with a
brush/cloth, working with the
grain
 Cover all surfaces evenly, with no
drips/runs
 When the first coat is applied,
allow to dry
 Sand lightly between coats (denib)
with very fine sandpaper or fine
wire wool
 Apply another coat of varnish
evenly and leave to dry again
 Repeat the process until you have
three coats applied

13. Microporous finishes
 Breathable skin
 Protect the wood from the
weather
 Allow moisture to
evaporate from the wood
 Do not flake or blister
 Environmentally friendly
 For external use, e.g.
sheds/fences

14. Danish oil
 Why choose Danish oil?
– Easy to apply
– Doesn't raise the grain
– Gives a nice shine
– Wood can be re-oiled
– Suitable for outdoor use

15. Danish oil – application
 Apply with a cloth, work oil well
into the grain
 Apply two or three coats and
leave to dry overnight
 De-nib any rough surfaces using
light sandpaper
 Apply another three coats of oil
 Gradually build up the finish using
the above process

16. Wax finishes
 Why choose wax?
– Easy to apply
– Does not raise the grain
– Gives nice lustre/shine
– Easy to renew
– Allows polish to be built
up
– No sanding between
coats
– Indoor use only

17. Wax finishes – application
 After surface finishing, seal the
wood with a wood sealer
 Using a clean dry cloth apply the
wax rubbing well into the wood
 Build up a number of coats before
letting the wax dry for a while
 Polish the surface to bring up a
shine
 Repeat the process to build up to
a high gloss shine
 Wax is a soft finish and is not
water-resistant, so it can only be
used indoors

18. Lacquer
 Applied by spraying
 Special equipment is
required
 Proper extraction
system is required
 Lacquer is harmful if
inhaled
 Spray gun

19. Quiz

20.  Why is it necessary to apply a finish to a wooden
artefact?
• Seals the wood
• Prevents dirt getting in
• Enhances the appearance
of the piece
• Protects the wood from
wear and tear

21.  What is used to clean a brush after applying oil-based
paint or varnish?
− White spirit

22.  List the steps required to prepare a wooden item for an
applied finish
Rub out/remove pencil lines
Scratches and marks can be removed using a scraper
Punch nails and pins
Fill nail holes and small cracks using a suitable wood filler
Sand the surfaces smooth using sandpaper
Sand end grain
Start with 100 grit (medium) sandpaper, then with 180 grit
and finally 320 grit (very fine)
− Always sand with the grain – avoid scratching the surface
− Brush off all dust or use a tack cloth
−
−
−
−
−
−
−

23.  Suggest a finish suitable for a picnic table and give reasons for
your choice
• Microporous varnish, e.g.
Fencelife
− Protects the wood
− Makes the wood look
good
− Allows the wood to
breathe
− Easy to apply
− Prevents decay
− Does not blister or flake

24.  Describe the steps in applying varnish to the unit shown
− Prepare the surface very well
− Apply varnish to the surfaces with a
brush or cloth, work with the grain
− Cover all surfaces evenly with no
drips/runs
− When the first coat is applied, allow to
dry
− Sand lightly between coats with very fine
sandpaper or fine wire wool
− Apply another coat of varnish evenly and
leave to dry again
− Repeat the process until you have three
coats applied