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    Categories: Arts

Chevreul’s illusion

During the 19th century, scientist-writers such as Michel Eugène Chevreul, Ogden Rood and David Sutter wrote treatises on color, optical effects and perception. They were able to translate the scientific research of Helmholtzand Newton into a written form that was understandable by non-scientists. Chevreul was perhaps the most important influence on artists at the time; his great contribution was producing a color wheel of primary and intermediary hues.

Chevreul was a French chemist who restored old tapestries. During his restorations of tapestries he noticed that the only way to restore a section properly was to take into account the influence of the colors around the missingwool; he could not produce the right hue unless he recognized the surrounding dyes. Chevreul discovered that two colors juxtaposed, slightly overlapping or very close together, would have the effect of another color when seen from a distance. The discovery of this phenomenon became the basis for the Pointillist technique of the Neoimpressionist painters.

Chevreul also realized that the ‘halo’ that one sees after looking at a color is actually the opposing, or complementary, color. For example: After looking at a red object, one may see a cyan echo/halo of the original object. This complementary color (as an example, cyan for red) is due to retinal persistence. Neoimpressionist painters interested in the interplay of colors made extensive use of complementary colors in their paintings. In his works Chevreul advised artists that they should not just paint the color of the object being depicted, but rather they should add colors and make appropriate adjustments to achieve a harmony. It seems that the harmony Chevreul wrote about is what Seurat came to call ’emotion’.

According to Professor Anne Beauchemin from McGill University, most Neoimpressionist painters probably did not read Chevreul’s books, but instead they read Grammaire des arts du dessin, written in 1867 by Charles Blanc, who cited Chevreul’s works. Blanc’s book was targeted at artists and art connoisseurs. Color had an emotional significance for him, and he made explicit recommendations to artists which were close to the theories later adopted by the Neoimpressionists. He said that color should not be based on the ‘judgment of taste’, but rather it should be close to what we experience in reality. Blanc did not want artists to use equal intensities of color, but rather to consciously plan and understand the role of each hue.

A Sunday afternoon at the Island of La Grande Jatte – Georges Seurat

Another important influence on the Neoimpressionists was Ogden Rood, who also studied color and optical effects. Whereas the theories of Chevreul are based on Newton’s thoughts on the mixing of light, Rood’s writings are based on the work of Helmholtz, and as such he analyzed the effects of mixing together and juxtaposing material pigments. For Rood, the primary colors were red, green, and blue-violet. Like Chevreul, he stated that if two colors are placed next to each other, from a distance they look like a third distinctive color. Rood also pointed out that the juxtaposition of primary hues next to each other would create a far more intense and pleasing color when perceived by the eye and mind than the corresponding color made by mixing paint. Rood advised that artists be aware of the difference between additive and subtractive qualities of color, since material pigments and optical pigments (light) do not mix together in the same way:

  • Material pigments: Red + Yellow + Blue = Black
  • Optical / Light : Red + Green + Blue = White

Via Georges Seurat

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