Wikimedia, Public Domain, Photograph by Paul Nadar
Michel-Eugène Chevreul was one of the most important chemists of nineteenth century in France. He also made significant contributions to the domain of color science. He was born on August 31, 1786, in Angers, France, to a family of surgeons and his father, Michel, was a well-known physician and the dean of the local medical school [1].
In 1818, Chevreul married Sophie Davallet, the daughter of a government tax official, and they had a son, Henri. After his wife’s death in 1862, Chevreul forsook almost all social life and resided in the Museum of Natural History in Paris [2]. At his centenary birthday, the French government minted a medal (depicted at the end of this article), published a beautiful copy of his color book, and celebrated his life as a national event. Chevreul received letters of commendation from many heads of state and monarchs, including Queen Victoria. In 1889, as his health declined, his son Henri came to be with him in Paris. However, sadly Chevreul suffered the death of his son 13 days before his own death on 9 April 1889 at the age of 102 [1, 2]. He was honored with a public funeral. In 1901, a statue was erected to his memory in the museum where he worked.
Chevreul’s childhood coincided with the midst of the terror of the French Revolution. He witnessed much violence and suffering, including in 1793, the execution of two young girls. As a result, he maintained a lifelong aversion to politics. He received private education before entering the Ecole Centrale, a new scientific school in Angers in 1799, where for four years he studied Greek, Italian, botany, mineralogy, mathematics, physics, and chemistry. He was not attracted to his family’s professional tradition of medicine. At the conclusion of his studies, he decided to become a chemist. In 1803, at around the age of seventeen, Chevreul left for Paris and entered Nicolas Vauquelin’s chemical laboratory as his assistant at the National Museum of Natural History and was placed in charge of the chemical analysis of samples [1, 2].
In 1810, at the age of twenty-four, Chevreul obtained his first position as an assistant naturalist at the Museum. Three years later, he became a professor of chemistry at the Lycée Charlemagne, one of the leading schools in France. His examination and analysis of the nature of animal fat, initially from a sample of soap, and the discovery of the different acids resulted in the publication of a book in 1823 that made him a famous chemist [3]. One year later, he published another book to explain the methodology that enabled him to make his discoveries [4].
Chevreul rose rapidly through the scientific ranks during the 1820s and 1830s. In 1824, he became director of dyeing at the Manufactures Royales des Gobelins, the national tapestry workshop and for nearly sixty years, he taught courses in chemistry at these two institutions. He was director of the Museum from 1864 to 1879 [5].
He produced books on the history and philosophy of science and continued his scholarly endeavors into the 1880s, his last publication appearing in 1888. During his career in the nineteenth century, he made significant strides toward a better understanding of chemistry. Chevreul excelled at the elemental analysis of organic substances and established the molecular formulas for many important chemical compounds. He established the melting point as a key criterion for the purity of a substance, a characterization technique, which is still in use today.
33.1 The Law of Simultaneous Contrast of Colors
Chevreul’s main responsibilities as director of the dyeing department at Gobelins were to look after the quality of the wool, the quality and stability of the dyes and their brightness, and the kind of cloth to which they had to be applied to (wool, silk, and cotton). As director of the department, Chevreul conducted a considerable amount of work on color. This included color classification, color application, as well as his most famous book The Principles of Harmony and Contrast of Colors and their Applications to the Arts, in 1839 (translated into English in 1854) [6], which was once considered one of the twelve most important books on color [7].
In the case where the eye sees at the same time two contiguous colours, they will appear as dissimilar as possible, both in their optical composition and in the strength of their colour. [6, 8]
If we look simultaneously upon two stripes of different tones of the same colour, or upon two stripes of the same tone of different colours placed side by side, if the stripes are not too wide, the eye perceives certain modifications which in the first place influence the intensity of colour, and in second, the optical composition of the two juxtaposed colours respectively. Now as these modifications make the stripes appear different from what they really are, I give to them the name of simultaneous contrast of colours; and I call contrast of tone the modification in intensity of colour, and contrast of colour that which affects the optical composition of each juxtaposed colour. [6, 9]
In the case of lightness differences, the modified appearance is an exaggeration of the difference. However, in the case of hue differences, the observed effect is dependent on what Chevreul considered complementary colors. He pointed out that red and green; orange and blue; greenish-yellow and violet; and indigo and orange–yellow are complementary colors [6, 10]. He noted that the modification of the appearance of juxtaposed colors consists of perceiving each color as slightly tinted with the complementary color of the juxtaposed one. If the two samples viewed are themselves complementary colors, e.g., red and green, the two hues will not be modified, rather they will be enhanced, thus red will appear redder and green will appear greener.
It should be noted that Chevreul was not the first to “discover” this phenomenon and others including Prieur had also noted this effect [11]. Chevreul acknowledged this and devoted a chapter to the experiments made by others [6]. However, he classified and structured these phenomena and carefully distinguished different kinds of contrast, including the simultaneous contrast, the successive contrast, and a mixed effect. Successive contract is observed when one or more colored objects are seen for a certain length of time in sequence resulting in their complementary colors being viewed [6]. Even though simultaneous contrast is often related to chromatic induction, successive contrast is generally associated with chromatic adaptation; for this reason, the concept of afterimages is often used today instead of successive contrast [5].
In the case of mixed contrast, the effects of simultaneous and successive contrasts are combined. This occurs when after having looked at one color for a certain length of time, another color is viewed. The resulting sensation is a combination of the second color and of the complementary color of the first one.
Chevreul’s chromatic circle containing main hues [9]
Chevreul gave many public lectures, which were attended by artists and practitioners and had a large influence on generations of artisans, even before the publication of his book on simultaneous contrast in 1839. This included many fields as diverse as tapestry and stained-glass restoration, to shop signs and gardening. His work also had a significant influence on painters, from the 1830s up to the beginning of abstract painting.
