Graphic

Colour

Colour is, of course, simply the way we describe light

of different wavelengths. When we see colour, we are really

seeing light. When we look around us, the light which enters

our eyes does so in three ways - directly, e.g. from a light

source such as the Sun or a light bulb, indirectly, by reflection from any smooth reflective surface, or by transmission

through a transparent material, such as coloured glass. When

we look at an object, the colour it appears to have depends

on which wavelengths of the light falling on it are absorbed,

reflected or transmitted. A yellow flower is yellow because it

reflects yellow light and absorbs other wavelengths. The red

glass of a stained glass window is red because it transmits

red light and absorbs other wavelengths. The process by

which we perceive the colours of natural objects around us

can therefore be described as a ’subtractive’ process.

Subtractive, because the objects ’subtract’ certain wavelengths

from the white light falling upon them before reflecting and/

or transmitting the wavelengths which determine their colour. The colours we see when we look at an original old master depend on the optical properties of the pigments used to

produce the original paint employed by the artist and on how

these properties may have altered over the centuries since

the work was created.

Some of the earliest cave drawings were created using

charcoal from burnt sticks mixed with a natural binder such

as animal fat, fish glue or the sap from plants, or using natural chalks - white calcium carbonate, red iron oxide or black

carboniferous shale. The first ’paint’ used by the earliest cave

painters was a crude rust-coloured paste made from groundup iron oxide mixed with a binder.

Colour was introduced to early three-dimensional works

of art by applying coloured pieces of glass, stone, ceramics,

marble, terracotta, mother-of-pearl, and enamels. Although

mosaic decoration was mainly confined to floors, walls and

ceilings, its use extended to sculptures, panels, and other

objects. Tesserae - shaped pieces in the form of small cubes -

were embedded in plaster, cement, or putty to hold them in

place.

By the time of the Ancient Egyptians, the artist’s palette of colours had expanded to include pigments predomi nantly made from mineral ores - azurite (blue), malachite

(green), orpiment and realgar (yellow), cinnabar (red), blue

frit and white lead. Additional pearly or pastel-like colours

offered by gouache - a form of watercolour which uses

opaque pigments rather than the usual transparent watercolour pigments - were also developed by the Egyptians. The

wall paintings of ancient Egypt and the Mycenaean period

in Greece are believed to have been executed in tempera - a

method of painting in which the pigments were carried in a

blue-purple organic pigment indigo, extracted from the In-

.dig0 plant, as well as Tyrian purple and the green copper oxide, verdigris. Many years later, the thirteenth century saw

the introduction of lead tin yellow, madder (red), ultramarine (blue green) and vermilion (red).

In contrast to the older water-based media, such as

fresco, tempera and watercolour, oil paints, developed in

Europe in the late Middle Ages, consist of pigments ground

up in an oil which dries on exposure to air. The oil is usually

linseed but may be poppy or walnut. In the late eighteenth

century the Industrial Revolution boosted the palette with

chromes, cadmiums and cobalts, but it was not until the following century that paint consisting of prepared mixtures of

pigments and binders became commercially available on a

wide scale.

In parallel with the gradual evolution of the types and

colours of paint available to the artist, inks used for printing

also evolved. Lampblack - a black pigment produced by the

incomplete burning of hydrocarbons - was in use in /4..7

China as early as AD 400.