treatments and finishes

Question 1

what needs to happen to wood before it’s finished

Answer 1

it has to be sanded

Question 2

why is it a good idea to apply a sanding sealer before sanding timber

Answer 2

otherwise, the first coat of varnish or wax could cause wood fibres to stick up

Question 3

before painting, wood needs to be primed, what does this do

Answer 3

• fills the grain of the timber to give the paint a smooth finish
• helps seal the timber, so paint won’t soak in and need to be reapplied
• helps the paint to stick better

Question 4

what are the two types of paints and what are they used for

Answer 4

• under coat - first coat of paint, covers up any previous colours more cheaply than applying to coat, helps layer layers paint or stick
• gloss paints - hard wearing, used on things like interior woodwork

Question 5

types of varnish and their uses

Answer 5

• yacht varnish - seals the wood and makes it waterproof, flexible, good for outdoor uses
• polyurethane varnish - best for interior like stairs as its very hard wearing, for the best result add 2 or 3 coats

Question 6

whats tantalising

Answer 6

a process used to prevent insect attacks and decay of wood, used in outdoor playgrounds, fences, telegraph poles

Question 7

how does tanalising work

Answer 7

1. seasoned timber is placed into a treatment tank
2. air is removed from the tank, creating a vacuum
3. the tank is flooded with the preservative
4. pressure is applied which forces the preservative deep into wood
   5 excess preservative is removed and timber is left to dry

Question 8

how can we smooth a metal

Answer 8

filing
- next, run the metal with abrasive paper and wet and dry paper

Question 9

why do we need to remove grease from the surface

Answer 9

to make sure the finishes will stick properly

Question 10

how can metals be finished

Answer 10

dip coating - metal coated with thin plastic, gives a soft, smooth finish
powder coating - object is sprayed with electrostatic gun, gives an even coat and there’s hardly any waste
galvanising - coating with zinc to make it corrosion resistant

Question 11

ways to finish polymers

Answer 11

• wet and dry paper
• buffing machine

Question 12

why don’t plastics need protective surface finishes

Answer 12

because they are very resistant to corrosion and decay