Paints are used to decorate surfaces or protect them from damage. A pigment is a coloured substance used in paint.
Paints contain these ingredients:
- a pigment - gives the paint its colour
- a binding medium – a liquid polymer that hardens to form a continuous layer when the paint dries
- a solvent - dissolves the binding medium and makes the paint more fluid
Oil paints have a hydrocarbon oil as the binding medium. This is dissolved in a solvent. The pigment is dispersed within this solution.
When the paint dries the solvent evaporates away, leaving behind the pigment and oil binding medium. The oil hardens to form a continuous layer of dry paint.
Emulsion paints are water-based - their solvent is water.
Colloids
Paints are a type of mixture called a colloid. In a colloid, particles of one substance are mixed and dispersed with particles of another substance - but they are not dissolved in it.
In an paint the pigment is dispersed in the liquid formed from the binding medium and solvent solution.
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