Paints and pigments Flashcards
What are the key features required in paint and what are they for?
> Pigment- for colour
Binding medium- sticks pigment to surface
Solvent- thins paint, easier to spread
What is the binding medium in oil paint?
oil
Why do we use paint?
> Protection- woodwork outside is painted to protect against rain. The oil sticks to the wood and forms a skin
Attractiveness- we enjoy the pigment (colour). The binder is used to stick pigment to the canvas or walls
What makes a good pigment?
- Does not fade
- Hides colour underneath
- Stays mixed throughout the binding medium
What is used to reduce the amount of pollutant released in paint when the solvent evaporates?
An emulsion paint contains less solvent
What happens once the oil paint has been painted onto a surface?
> the solvent evaporates
the binding medium dries, forming a skin
the skin sticks the pigment to the surface
What is emulsion paint?
- A water-based paint that contains only a small amount of oil.
- The oil is still the binding medium with pigment particles dispersed through it
- The oil is in the form of small droplets spread through water
- This is because oil does not mix with water
Why is pigment not dissolved in the binding medium and solvent?
It forms a colloid of small solid particles dispersed through the whole liquid, but they are not dissolved.
What is emulsion?
When tiny droplets of one liquid is in another liquid
What happens when an emulsion paint is painted onto a surface?
> the water evaporates
the droplets of oil join together to make a continuous film
the skin sticks the pigment to the surface
What are colloids?
> mixtures of tiny particles of one thing in another
>oil paint is a colloid because it is a mixture of solid particles in liquid
What evaporates when oil paint dries?
The solvent
How is emulsion paint a colloid?
> It is a mixture of one liquid inside another - oil droplets in water
Each oil droplet also has solid particle in it
