Flashcards in C1H - Paints & Pigments Deck (22):
What does a solvent do in paints ?
Thins it and makes it easier to spread
What gives the paint it's colour ?
What's a binding medium ?
A liquid that carries the pigments and holds them together. When it turns solid it sticks the pigments to the surface you've painted.
Paints are what ?
What do colloids consist of ?
Really tiny particles of one thing dispersed in another thing. But they are NOT dissolved. Just mixed in.
What can the particles be in a colloid ?
Bits of solid
Droplets of liquid
Bubbles of gas
Why don't colloids separate out ?
Because the particles are so small they don't settle at the bottom
Are the particles in a colloid heavy ?
No light so they can stay dispersed
Describe an emulsion paint ?
They are water based. Their solvent is water and the binding medium is usually an acrylic or vinyl acetate polymer
Describe an Oil paint ?
They are oil based. The solvent is an organic compound that dissolves oil and the binding medium is oil.
How does an emulsion paint dry ?
The solvent which is water evaporates leaving behind the binding medium and the pigment as a thin solid film.
How does an oil paint dry ?
The solvent evaporates. Then the oil which is the binding medium is oxidised by oxygen in the air. Then it turns solid.
Lily is painting her room. Her dad tells her to use oil paints. Why would this be a bad idea ?
It takes longer to dry and the solvent can produce harmful fumes
Why would someone paint their bike ?
In order to stop it from rusting
What kind of pigments change colour when heated ?
What kind of things would you use thermochromic paint for ?
What kind of pigments are in thermochromic paints ?
Heat sensitive pigments
What can we mix thermochromic pigments with ?
Acrylic paint. For novelty mugs.
What pigments glow in the dark ?
Explain how phosphorescent pigments work in two stages.
They absorb natural or artificial light and store the energy in their molecules.
Then this energy is released as light over a period of time. From seconds to hours
What uses are their for phosphorescent pigments ?
Emergency exit signs
Glow in the dark watches