Colour: optical colour mixing

Duration One hour

Materials Palette, palette knife, a range of brushes, three sheets of primed white paper, paints: cadmium lemon; cadmium yellow; cadmium red; alizarin crimson; cobalt blue; ultramarine blue

What will I learn?

When two hues are placed side by side or on top of each other, your vision produces the illusion of a third colour - this is called optical mixing. Optical mixtures emit an inner glow that you cannot get with physical mixtures - the colours retain their intensity and brightness.

The best example of this is found in work by the pointillists, who laid down small dots of different colours and allowed the viewer to optically mix them. These paintings were informed by the law of contrast noted by colour theorist ME Chevreul. Chevreul observed that any colour is heightened when placed beside its complement, so for example a red will seem redder and a green greener when the two are placed side by side.

Here, you will paint small coloured dots side by side, which will enable you to create areas of scintillating colour. When you paint dots of analogous colours, new hues and luminosity emerge. When dots of complementary colours are used, you can create luminous grey mixtures. You will start to see the difference between optical mixing and mixing on a palette, which creates duller colours.Method

Here you will make three compositions of dots painted very close together against a white background. Remember that dots can be individual shapes and not necessarily small circles.

1. First, paint the three pure hues of yellow, red and blue as repeated dots. Daub on to the surface, dot by dot, with extreme precision. Different combinations of the pure hues will reveal colours such as red-violet, orange, blue-violet, and green.

2. On another background, build up layers of green and red dots. These generate greyish shadows.

3. On the last background, place blue, green and yellow dots close together. These will stimulate the eye to mix bright greens.

What do the results show?

There are many different ways to make colours interact. To use optical mixing in your paintings, remember the exact hues, intensities, quantities and lighting conditions that created the best optical mixes. All of these things affect how the eye plays with colour.

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