1. Module C2: Rocks and Metals
C2a Paints and Pigments
• State that a pigment is a coloured substance that is used in paint.
• Paints are made from:
1. ______________ - this gives the paint its colour
2. ______________ – this makes the paint thinner (more runny) so
that is can be brushed on easily.
3. _____________________ – this hardens as it dries and sticks the
pigment to the surface being painted
Paints as colloids
• Paint is a mixture called a colloid
• A colloid is a mixture made from a ___________with tiny particles of ______
dispersed (spread out) in it but NOT dissolved
e.g. emulsion paints are water based (solvent) with tiny droplets of
polymer dispersed throughout (binding agent).
• Oil paints have the ______________ dispersed in oil and often a _________
that dissolves oil.
• The components of a colloid will not separate because the dispersed
particles are __________________ to settle to the bottom.
Why do we use paints?
How do paints work?
1. Paints are applied as a ______________ layer to a surface.
2. The solvent ______________________ and the paint dries.
3. The binding agent reacts with ____________ in the air and hardens, sticking the
pigment (colour) to the surface.

2. Dying Fabrics
• Dyes are used to colour fabrics.
• Some dyes are ________________ and others synthetic (_____________).
• The use of synthetic dyes has increased the number of colours available to
colour fabrics.
Thermochromic Paints
• Thermochromic pigments change colour when ______________ or cooled.
• Uses of thermochromic pigments:
• Thermochromic pigments can be added to ____________ paints to give even
more colour changes.
Phosphorescent Pigments
• Phosphorescent pigments can _____________ in the dark.
• Phosphorescent pigments _______________ and store energy and release it
as _____________ over a period of time.
• Phosphorescent pigments are much safer than the alternative radioactive
substances
e.g. in use of ‘glow in the dark’ watches.