The scientific approach of Newton
Isaac Newton (1642-1727) is considered the father of the science of colour. However, Thierry von Freiberg (13th century) was probably the first to give a convincing explanation of the rainbow spectrum. He observed the scattering of daylight through spherical glass flasks, filled with water. Freiberg suggested that the drops of water suspended in the atmosphere after rain behaved as spherical balloons filled up with water.
Newton observed the scattering of a light ray through a prism of glass placed in an obscure room. He showed that the visible light was made up of a spectrum of colour radiations and that the recombination of these radiations gave the visible (known as white) light again.
The father of the theory of gravitation naturally thought that light was made of corpuscles of distinct masses according to the colours. On the contrary, the contemporary science emphasises more the undulatory aspect of light and classified colour radiations according to one criterion only, the wavelength.
The artists could not be satisfied with this statement only. Did a genius painter as Eugène Delacroix not say in his diary!
“Colour is par excellence the part of the art which holds the magic gift. Whereas the subject, the form, the line are initially addressing the thinking, the colour does not make sense for intelligence, but has all powers on sensitivity.”
Eugène Delacroix said that he had found his colour theory while painting the canvass entitled “Execution of the Doge Marino Faliero” (1826):
He discovered that purple shades better emphasized yellow and drew the coloured star, consisting of two reversed triangles, on a wall of his workshop:
- The first triangle contained the primary colours yellow, red and blue which could not be obtained by mixing other colours;
- In the reversed triangle appeared the secondary colours purple, green and orange obtained by mixing two by two the primary colours;
- The opposite colours of the star represented the complementary colours whose mixing gave a neutral gray.
In the past, beings sensitive to the perception of colours had already raised criticisms about Newton's approach. In fact, light became visible in darkness only. For Newton, darkness was absence of light only. However, black and its gray gradations played a significant role in the shades projected by light falling on an object. It was impossible to speak about light without evoking darkness in various degrees and conversely. An author as Johann Wolfgang von Goethe (1749-1822) proposed a more global approach of colour based on the alliance of light and darkness.
The sensory approach of Goethe
In his poetic work “Faust” (first part 1808 and second part 1832), Goethe had already evoked the fight between light and darkness. He undertook a work on light and dark for forty years and regarded his “Treaty of colours” (1808 to 1810) as his most important work after “Faust”.
Goethe particularly studied shades by the light of the rising sun; the rocks took an orange colour and their shade a blue-green one. Considered separately, the shade was quite gray, but replaced in its coloured environment, it became blue-green, the complementary colour to orange. This phenomenon, considered by science as an optical illusion, was however well perceived by the eyes of the observer 1. For Goethe, the perception of colours was above all of sensory nature; he described the colours as he saw them.
The author of the “Treaty of colours” knew of Newton's experiments and undertook them again in daylight with prisms of various angles. He observed, through a prism, the images of two complementary rectangles, a white rectangle on a black background and a black rectangle on a white one:
The experiment gave surprising results. Instead of a single colour spectrum, two marginal spectra appeared at the edges of each of the white and black rectangles:
We note that both spectra of the black rectangle are inverted compared to those of the white rectangle.
When the height of the rectangles decreased, the marginal spectra approached until practically touching each other:
The continuation of the reduction of the height of the rectangles led to the overlapping of the marginal spectra. Yellow and blue mixed in the white rectangle to give the green colour and the Newton's spectrum; similarly, purple and red mixed in the black rectangle to give the crimson colour and a second spectrum proper to Goethe.
While pushing further the reduction of the height of the rectangles, two spectra of three colours only appeared.
Goethe gathered both spectra and the results of his observations in his “chromatic circle”:
For the poet, the first triangle represented the light colours (blue-cyan, crimson and yellow), whose mixing gave the colour of the black rectangle on a white background, i.e. light was hiding behind dark. The reversed triangle grouped together the dark colours (red-orangey, green and purple), whose mixing gave the colour of the white rectangle on a black background, i.e. dark was hiding behind light. Light and dark were indissolubly linked in Goethe's vision of colours. Every colour is simultaneously associated with light and dark.
Unlike Newton, Goethe considered that light was invisible; only the manifestation of colours made it visible in the eyes of the observers. This dialogue between the invisible and its visible manifestation showed not only a sensory, but also a spiritual approach. Consequently, Goethe's interest for the relationship between the parts and the whole and its fundamental polarity of light and dark was therefore not surprising. Such an approach was developed in painting by the great English artist William Turner. How not to draw a parallel between the colours of the three lower stripes of the painting entitled “Colour beginning” (1819) and the colours of the spectrum proper to Goethe!
However, the artist had not been aware of the book of the poet at the time of the canvas realization. These two geniuses must have been driven by a common vision of colour based on the observation of the world as a whole.
If colour is a concern of the outer world for most scientists, it reveals our inner world for Goethe.