The
origin of Colour
Mixing of Colours
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| Light
as the source of colour Thanks to light we are able to perceive colours. In the dark we see nothing. White light is made up of all the colours of the rainbow. A triangular piece of glass, a prism, demonstrates this. If a beam of light passes through a prism, the different colours become visible. We call this series of colours the spectrum. In addition at either end of the spectrum there are invisible rays - at the red end infrared, at the blue end ultraviolet (ill. 1). |
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Reflection
and absorption Most colours do not originate directly from a light source. They are created by an interplay of light, the human eye and colorants. Trees, flowers and fruits, human beings and animals, stones and even earth allow us to see countless colours without themselves generating light. They exhibit colours through colorants. These substances have the property of absorbing a particular part of the spectrum and reflecting another. If we see a red object under white light, then this item contains a colorant which absorbs the yellow, orange, purple, blue and green components of the light. Only the red component is reflected back to our eyes. (ill. 2). |
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| And what about white, black and grey? In theory these are not colours. A white object contains a substance which does not absorb any colour in the spectrum. The whole spectrum is reflected. With black we see the opposite. No colour is reflected, all the colours in the spectrum are absorbed. Grey is somewhere between white and black. An equal quantity of each colour is reflected, the rest is absorbed. The reflected colours mix to become grey. The lighter the grey (the further in the direction of white), the more of each colour is reflected. And vice versa. (ills. 3, 4, 5). |  |
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However,
these examples are purely theoretical. In reality there are no
substances which totally absorb a certain part of the spectrum and
reflect a hundred percent of another. We can illustrate this with the
colour red. From the many shades of red we shall select vermilion to
begin with. If we check what portion of the spectrum is reflected in
this red, we find that the red portion is the main one. But we see too
that all the other colours are also present, especially orange and
yellow (ill. 6). |
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| Let us now look at the pink colour magenta. Here too the red portion of the spectrum again proves to be most evident. But equally all the other colours, notably purple and blue are also found (ill. 7). |
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To summerize no colour is
completely pure. Every colour contains traces of all other colours.
The colour most evident after the principal colour, will affect the
principal colour. White, black and grey too are only pure in theory.
An exactly identical amount of each colour is never reflected.
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Mixing
of Colours
WE CAN MIX COLOURS IN TWO WAYS: WITH LIGHT AND WITH COLOUR. MIXING WITH COLOURED
LIGHT IS CALLED ADDITIVE MIXING. THE MORE COLOURS THAT ARE ADDED, THE
LIGHTER THE RESULT. ALL THE COLOURS TOGETHER FORM WHITE LIGHT.
| Mixing with paint is
called subtractive mixing, which in this context means that light
is taken away. The mixed colour is always darker than the lightest of
the colours with which it has been mixed. Every colorant absorbs a certain section of the spectrum. If we mix two colours, different sections of the spectrum are absorbed. Only the jointly reflected section is left. We shall mix colours with colours, i.e. subtractively. We shall do this according to the three-colour mixing system and the six-colour mixing system. We shall also look at the phenomenon of optical mixing of colours. |
| Three-colour mixing
system Primary colours With the three primary colours lemon yellow, cyan (blue) and magenta (red) we can mix any colour tone we wish. These colours are called primary because they cannot be mixed from other colours. The principles of mixing can be learned using primary colours. Talens supplies a special gouache mixing set. In addition to the primary colours this contains white and black. The Ecoline range also contains the primary colours. To begin with, we mix yellow with blue, blue with red and red with yellow. That gives us green, violet and orange respectively (ill. 1). The proportion in which the colours are mixed depends on the colour intensity of the paint. It is a good idea to begin by mixing small quantities to avoid wasting paint. |
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| If we mix the colours next to each other in the six-colour circle, we obtain six new colours (ill. 2). By doing the same with the colours in the 12-colour circle we obtain twelve new colours. |
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| The 24-colour circle contains various yellows, greens, blues, etc. There are yellows with red traces and yellows with blue traces, bluish violets and reddish violets. By constantly mixing adjacent colours the circle can in principle be expanded into infinity. The colour areas merge into each other like the colours of the spectrum. |
| Primary
colours with white and black Countless colour tones can be mixed with the three primary colours. With white and black we can mix countless greys. By combining these two possibilities we can in principle mix any colour we like. Primary colours with white, without black The colours that we need to paint all the objects that surround us can also be mixed without black. Black and grey objects have more colour than is apparent at first sight. If we mix primary colours in the right proportion we create a grey which is almost black. This is because in the mixing only the jointly reflected section of the spectrum remains. When the primary colours are mixed that section is very small. Almost no light is reflected. This dark grey is dark enough to create the impression of black in a painting. This dark-grey can also be mixed instead of black with white and a colour tone into any colour required (ill. 3). |
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Colours opposite each other in the circle are called complementary colours. Two complementary colours together contain the three primary colours. Mixed in the right proportion these also create black colours, and of course greys as well with the addition of white (ill. 4). |
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| Orange, green and violet are called secondary colours. Two secondary colours combined also contain the three primary colours. However, they do not cancel each other out as completely and we do not obtain a black colour. Whatever proportion they are mixed in, the common primary colour is always dominant and hence determines the colour. A colour mixed from two secondary colours is called a tertiary colour (ill. 5). |
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| Three secondary colours combined in turn contain equal quantities of the three primary colours so that a black colour can also be mixed from them, as well as greys in combination with white. |
| Limitations
of the three-colour mixing system Lemon yellow, cyan blue and magenta are saturated colours. Nevertheless the three-colour mixing system has the limitation that the saturation of intermediate colours may be greatly reduced. The following examples illustrate this: Lemon yellow is a yellow with blue traces. Cyan is a blue with yellow traces. Magenta is a red with blue traces (ill. 6). |
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The violets mixed from cyan blue and magenta contain, in addition to blue and pink, the yellow traces of the blue. Yellow and violet are complementary colours. Equal parts of yellow and violet make grey when mixed, so that the violets are less saturated (ill. 7). |
| The saturation of the oranges is sharply reduced as a result of the complementary traces of both pink and yellow (ill. 8). |  |
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Only
the greens are saturated. The colour tone of both lemon yellow and cyan
blue have no traces which do not belong to the green part of the
spectrum (ill. 9). |
| Six-colour
mixing system In order to be able to make a colour circle with only saturated colours, we add three new colours: ultramarine (a blue with red traces), a yellow with red traces and vermilion (a red with yellow traces). Orange and violet are now also saturated (ill. 10). |
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| By mixing
adjacent colours the circle can be further expanded. By adding white, grey or black the brightness and saturation of each colour tone can of course be changed, just as in the three-colour mixing system. The six-colour mixing system also offers more opportunities for approximating black. The yellows, reds and blues can be mixed in different combinations. The proportion in which they are mixed determines the colour tone of the dark grey. If we want to mix a grey without a colour tone, a neutral colour, those proportions must be very precise. The darkest neutral grey is obtained by mixing all six colours. This grey is so close to black that the difference can only be seen when compared with pure black paint. |
| Optical
mixing of colours Pointillistic mixing Pointillism means painting with dots. To obtain a green colour we do not mix yellow and blue paint, but paint yellow and blue dots close together on a surface. The surface will then give the impression of being green. The smaller the dots the more complete the mixture will appear (ill. 11). Here too complementary colours make the mixed colour unsaturated (dirty). |
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If we combine coloured dots with white, black or grey ones, brightness and saturation are affected in the same way as in ordinary mixing (ill. 12). |
Even without black dark grey colours can be suggested through pointillism, although the result will never be as dark and unsaturated as in complete mixing (ill. 13). |
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| Glazing
mixing In painting glazing means the application of transparent layers of paint. A transparent blue applied over yellow mixes optically to green. Transparent red over yellow mixes optically to orange. Transparent blue over red mixes optically to violet. If we apply three colours on top of each other they cancel each other out and mix optically to produce an unsaturated grey colour (ill. 14). The best results are achieved with glazing mixing when increasingly dark colours are applied over each other. |
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| This technique cannot be used with gouache, since it is opaque. With all other types of paint the rule is that only colours based on (semi-)transparent pigments are suitable for this technique (see under pigments). |