The chrome colors were in use by 1816 but on a limited basis. In 1820, a substantial source of chrome ore was found in North America and large scale production began, j. J. White of Rutherglen, Scotland is known to have produced chrome colors that year. Their excellent hiding power and low cost made them a welcomed alternative to Turner's Patent yellow and orpiment. Chrome yellowcost one shilling per watercolor cake in 1835 (Harley 1970, 93). Although less poisonous than orpiment, they were toxic as well, due to their lead content. They were fast drying in oil and more permanent in oil than in watercolor. The darker shades were more permanent than the lighter ones that tended to fade when exposed to sunlight. The darker shades were known to brown over time (Doerner 1934, 62-63). All chrome colors were blackened by sulfur-bearing air and the yellow variety sometimes would turn green when mixed with organic pigments.
They are microscopically identified by their crystalline particles, the deeper shades having a more rectangular shape (Gettens and Stout 1966, 106). The lighter, more yellow shades have finer particles (Doerner 1934, 75). They are identified chemically by a change to black in sodium sulfide. In nitric acid, the orange turn's bright yellow and the yellow is only slightly affected. In other acids, the yellow turns red (Laurie 1914, 54).
Chrome green was developed sometime in the first quarter of the nineteenth century. Its discovery was possible because of Vauquelin's research. It was a homogeneous mixture of chrome yellow and Prussian blue. Chrome green was made by thoroughly mixing Prussian blue with a paste of barytes, china clay and chrome yellow. It is so chemically united that its separate parts cannot be distinguished microscopically, unlike a color that is mixed on the artists' palette. It had excellent hiding power and was inexpensive but was not lightfast due to the darkening of its chrome yellow component (Gettens and Stout 1966, 105). It is identified chemically by the disappearance of the Prussian blue upon treatment with caustic soda (Laurie 1914, 55).
Three more yellows were developed from Vauquelin's element. They were all sold under the name Lemon yellow and were introduced to the artists' palette around 1830 (Paint and Painting (1982, 17). The most permanent of these was strontian yellow (SrCr04). Mixing solutions of strontian chloride to neutral potassium chromate (Gettens and Stout 1966, 159) made it. Barium yellow (BaCrO4) was made much the same way as strontian yellow except barium chloride replaces the strontian. The third was zinc yellow (3ZcCrO4.K2Cr207), a double salt solution with potassium chromate (Wehlte 1982, 87).
Strontian yellow was a cool, light yellow but richer in tone than barium yellow (Doerner 1934, 64). All three were semi-transparent; strontian yellow was the most opaque. They were used in both oil and watercolor. Like all chrome colors, they tended to turn greenish in oil. Zinc yellow was the only non-toxic chrome color. Field is said to have introduced barium yellow in England as a less costly alternative to Platina yellow that was made from platinum (Harley 1970, 95). Blockx preferred barium yellow also. He found its permanence to be outstanding after thirty years and that it had an additional advantage of being mixable with all other pigments (Blockx 1910, 77).
Barium yellow is observed as lozenge-shaped extremely fine particles; less fine are the crystalline particles of strontian yellow (Gettens and Stout 1966, 159), distinguished chemically because it is the only one which does not turn black in hydrochloric acid (Wehlte 1982, 87).
By 1885, an imitation strontian yellow was invented. It resembled the original but contained no strontium. It was said to have been more durable than the original (Field 1885, 126).
Two other green pigments also resulted from the development of chromium. Their excellent permanence and lack of toxicity could replace all other greens, both ancient and modern. A color maker in Paris, Pannetier, first sold opaque oxide of chromium, as an artist's pigment in 1838. Viridian or transparent oxide of chromium followed in 1859.
Oxide of chromium, opaque (Cr203) was made by heating potassium bichromate with boric acid or sulfur until its water was lost and a powder was formed (Gettens and Stout 1966, 107). It was prepared for both oil and watercolor but its extreme opacity made it a poor watercolor. Its color tone was cool and dull (Field 1885, 136).
The transparent variety, viridian (Cr203.2H20) began its production in the same way as the opaque variety but the hot powder was put into vats of cold water until it acquired two water molecules. A bright, bluish green resulted which had excellent tinting strength. Guignet of Paris patented the process for manufacturing viridian in 1859 (Gettens and Stout 1966, 173).
Although viridian required much more oil to grind it as an oil paint (fifty to one hundred percent) compared to thirty percent in the opaque variety, both were good driers. Viridian, however, is prone to cracking if one misuses this transparent pigment too thickly (Wehlte 1982, 125-128).
They are distinguished microscopically by their large particle sizes (Gettens and Stout 1966, 173). They differ in that viridian's particles are slightly rounded and the opaque variety has coarse particles. They are insoluble and unchanged in chemical tests (Laurie 1914, 55).
Viridian was known as Permanent green when sold as a mixed green with zinc or cadmium yellows in the second half of the nineteenth century (Doerner 1934, 84).
Vauquelin is sometimes also credited with the development of Iodine Scarlet (also known as Pure Scarlet). In about 1811 or 1812, iodine was discovered by a French manufacturer of saltpeter. In 1814, Sir Humphrey Davy brought some iodine back home with him to England and published proof that it was an element. Vauquelin published the preparation of Iodine Scarlet and other iodine compounds in 1814 in Annales de Chimie XC. His article "Des experiences sur l'iode" described a simple recipe involving the grounding with a stone mortar iodine and mercury which quickly united to form an intense red hue. More detailed instructions for its preparation were published by Mérimée in 1830. He also mentioned that in England the pigment is sometimes sold as scarlet lake (Harley 1970, 118).
Iodine scarlet (HgI2) was known to have great body and opacity and more brilliance than vermilion. It was, however, a very fugitive color that could only be mixed on the palette with an ivory knife as metal knives turned it black. Iodine scarlet could not be mixed with other metallic pigments. Field said that" ... certainly nothing can approach it as a colour for scarlet geraniums; but its beauty is almost as fleeting as the flowers" (Field 1885, 107-108).
Zinc has been known as a mineral since antiquity when it was melted with copper to form brass. It was also known then, as it is today, as a medicinal ointment. Sources differ on who first isolated the element. Harley and Wehlte claim it was Henkel in 1421 who first produced metallic zinc. Gettens and Stout maintain it was the German chemist, Margraaf in 1746. Historians agree, however, that in 1782, zinc oxide was suggested as a white pigment. Guyton de Morveau at L'Académie de Dijon, France, reported on white pigments and the raw materials which might serve as white pigments, including zinc oxide in that year. He suggested zinc oxide as a substitute for white lead. Although the pigment became very important to nineteenth century painters, it never replaced the ancient lead White.
Metallic zinc had originally come from China and the East Indies. When zinc ore was found in Europe, large-scale production of the extracted metallic zinc began. In 1794 and 1796 patents were issued for the manufacture of zinc oxide to the English colormaker John Atkinson of Harrington Near Liverpool (Harley 1970, 166).
The French method of manufacturing, known as the 'indirect process' used the zinc smoke derived from molten zinc, which was heated to 150°C and collected in a series of chambers. This early form of zinc white was not accepted by artists because of its slow drying time in oil and poor covering power (Gettens and Stout 1966, 177). In 1803, Julius Caesar Ibbetson wrote An Accidence or Gamut of Painting in Oil and Watercolors, London, and said, "White lead is the only white we have of sufficient body to use in oil. White has been made from zinc, but it has not sufficient substance." A zinc white watercolor was available at that time which was made with liquid silver (Harley 1970, 167).
Zinc white was accepted as a watercolor by 1834 but it was some years later before its difficulties in oil were overcome. In 1834, Winsor and Newton, Limited, of London, introduced a particularly dense form of zinc oxide which was sold as Chinese white. It was different from former zinc white in that the zinc was heated at much higher temperatures than the late eighteenth century variety (Paint and Painting , 18). The name 'Chinese white' is said to have come from the oriental porcelain that was very popular in Europe in the eighteenth and nineteenth centuries (Pavey 1984, 30). George H. Backhoffner of London disputed Winsor and Newton's claim of their superior white watercolor in his book Chemistry as Applied to the Fine Arts, London, 1837. Backhoffner recommended Flemish white as superior-a white lead. Winsor and Newton believed that although scientists would ignore Backhoffner, artists would not use the Chinese white because Backhoffner lectured widely in the Art Academies and his opinion would be well known to them. In 1837, Winsor and Newton published a response to Backhoffner in Remarks on White Pigments used by WaterColour Painters and distributed copies to the artists. They were successful in convincing artists of the superiority of Chinese white because the name is still synonymous today for all zinc white in watercolor (Harley 1970, 168).
By 1844, a better zinc white for oil was developed by LeClaire in Paris. He ground the zinc oxide (ZnO) with poppy oil that had been made fast drying by boiling it with pyrolusite (Mn02). In 1845, he was producing the oil paint on a large scale (Harley 1970, 168). By 1850, zinc white was being manufactured throughout Europe.
Zinc white was still a slow drying white requiring twenty-three parts of oil to one hundred parts of pigment whereas lead white requires fifteen parts of oil. Zinc is essentially permanent in sunlight although the yellowing in oil affects its brightness (Laurie 1926, 83). It had advantages over white lead because it was not blackened by sulphur-bearing air or other pigments containing sulphur, as lead is (Blockx 1910, 59-60). It is non-toxic and more economical than white lead. Unlike lead white, it was prone to become brittle and crack over time. The general consensus was that both whites should be employed in oil painting because each had advantages over the other. Mixtures of both were common.
Since zinc oxide is derived from smoke fumes, its particles are very fine and are difficult to observe except at very high magnification. It readily dissolves in alkaline solutions, acids and ammonia without foaming (Gettens and Stout 1966, 177).
Stromeyer discovered metallic cadmium in 1817 but production of the cadmium pigments was delayed until about 1840 because of the scarcity of the metal (Harley 1970, 95). A natural mineral, green ochite, is known in nature but was not used for pigments (Paint and Painting , 18). Cadmium Sulfide (CdS) was prepared with an acid solution of cadmium salt (either chloride or sulfate) which was heated with hydrogen sulfide gas until a powder was formed. Hues ranging from a lemon yellow to a deep orange were made in this way (Gettens and Stout 1966, 101-2). Cadmium red was not made until about 1910 (Paint and Painting , 18).
The deeper varieties of cadmium yellow and orange were the most permanent (Laurie 1926, 88). The paler varieties were known to fade on exposure to sunlight (Laurie 1926, 88). All of the cadmiums were brilliant and the deeper shades had the greatest tinting strength. Field claimed that the best cadmiums were those produced without an excess of sulfur and that the permanence of a carefullyy made cadmium was improved when mixed with lead white using only an ivory knife (Field 1885, 123). They were used in both oil and watercolor but could not be mixed with copper-based pigments (Doerner 1934, 65).
The particle sizes of the deeper cadmiums are about fifty times larger than the paler varieties (Gettens and Stout 1966, 102). They are transparent particles that appear in clusters, microscopically. Cadmium pigments are dissolved in hydrochloric acid and nitric acids and are unchanged by sodium sulfide (Laurie 1914,51).
Ultramarine blue, artificial is one of the best-documented pigments of the nineteenth century probably because its invention was requested of chemists and not the result of their independent research. Ultramarine, genuine made from the semi-precious gem lapis lazuli was so costly in the nineteenth century that artists infrequently used it. The hue is a necessary component in a balanced palette of warm and cool colors; without it a cool, deep blue is lacking.
The beginning of the development of ultramarine blue, artificial was known from Goethe. In about 1787, he observed the blue deposits on the walls of lime kilns near Palermo in Italy. He was aware of the use of these glassy deposits as a substitute for lapis lazuli in decorative applications. He did not, however, mention if it was suitable to grind for a pigment (Plesters 1966, 76). The blue deposits were also taken from the Saint Gobain glassworks by M. Tessäert who found them in a soda furnace (Gettens and Stout 1966, 163). Tessäert was reportedly the first to suggest to the Societé d'Encouragement pour L'Industrie Nationale that a method for making a synthetic ultramarine should be investigated. He gave his blue samples to Vauquelin. In 1814, Vauquelin published his findings that the blue masses were similar in composition to the costly lapis lazuli in the Annales de Chimie LXXXIX, "Note sur une couleur bleue artificiale analogue a l'outremer" (Gettens and Stout 1966, 163). In 1824, the Societé d'Encouragement offered a prize of six thousand francs to anyone who could produce a synthetic variety not to exceed three hundred francs per kilo. The prize was not awarded for four years because all that was submitted to them were imitations based on cobalt or Prussian blue without regard for the analysis of the gem which was published in 1806 by Désormes and Clément.
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