Cerulean

The primary chemical constituent of the pigment is cobalt(II) stannate (Co
₂SnO
₄).[5][6][7] The pigment is a greenish-blue color. In watercolor, it has a slight chalkiness. When used in oil paint, it loses this quality.[8]

Today, cobalt chromate is sometimes marketed under the cerulean blue name but is darker and greener[lower-alpha 1] than the cobalt stannate version.[lower-alpha 2] The chromate makes excellent turquoise colours and is identified by Rex Art and some other manufacturers as "cobalt turquoise".[9][10]

Cerulean is inert with good light resistance, and it exhibits a high degree of stability in both watercolor and acrylic.[11]

• 
  Cerulean blue PB35
• 
  A sample swatch of cerulean blue hue oil paint. "Hue" in this instance means that other pigments have been used to mimic the color of oil paint that contains the original pigment.
• 
  Cerulean blue pigment in oil. On the left as a standoil glaze over zinc white; on the right as a mass tone in oil-based paint.

Cobalt stannate pigment was first synthesized in 1789 by the Swiss chemist Albrecht Höpfner by heating roasted cobalt and tin oxides together.[12][13] Subsequently, there was limited German production under the name of Cölinblau. It was generally known as Höpfner blue from the late eighteenth century until the middle of the nineteenth century.[3]

In the late 1850s, art suppliers begin referring to the pigment as "ceruleum" blue. The London Times of 28 December 1859 had an advertisement for "Caeruleum, a new permanent colour prepared for the use of artists." Ure's Dictionary of Arts from 1875 describes the pigment as "Caeruleum . . . consisting of stannate of protoxide of cobalt, mixed with stannic acid and sulphate of lime." Cerulean was also referred to as coeurleum, cerulium, bleu céleste (celestial blue). Other nineteenth century English pigment names included "ceruleum blue" and "corruleum blue". By 1935, Max Doerner referred to the pigment as cerulean, as do most modern sources, through ceruleum is still used.[3]

Some sources claim that cerulean blue was first marketed in the United Kingdom by colourman George Rowney, as "coeruleum" in the early 1860s. However, the British firm of Roberson was buying "Blue No. 58 (Cerulium)" from a German firm of Frauenknecht and Stotz prior to Rowney.[3] Cerulean blue was only available as a watercolor in the 1860s and was not widely adopted until the 1870s when it was used in oil paint. It was popular with artists including Claude Monet, Paul Signac, and Picasso. Van Gogh created his own approximation of cerulean blue using a mixture of cobalt blue, cadmium yellow, and white.[14]

In 1877, Monet had added the pigment to his palette, using it in a painting from his series La Gare Saint-Lazare (now in the National Gallery, London). The blues in the painting include cobalt and cerulean blue, with some areas of ultramarine. Laboratory analysis conducted by the National Gallery identified a relatively pure example of cerulean blue pigment in the shadows of the station's canopy. Researchers at the National Gallery suggested that "cerulean probably offered a pigment of sufficiently greenish tone to displace Prussian blue, which may not have been popular by this time."[15]

Berthe Morisot painted the blue coat of the woman in her Summer's Day, 1879 in cerulean blue in conjunction with artificial ultramarine and cobalt blue.[16]

When the United Nations was formed at the end of World War II, they adopted cerulean blue for their emblem. The designer Oliver Lundquist stated that he chose the color because it was "the opposite of red, the color of war."[17]

In the Catholic Church, cerulean vestments are permitted on certain Marian feast days, primarily the Immaculate Conception in diocese currently or formerly under the Spanish Crown.[18]

• 
  Claude Monet, La Gare Saint-Lazare, 1887
• 
  Berthe Morisot, Summer's Day, 1879
• 
  Symbol of the United Nations

• Cerulean cuckooshrike
• Cerulean kingfisher
• Cerulean flycatcher
• Cerulean warbler
• Cerulean-capped manakin

• The Devil Wears Prada (film) § Cerulean sweater speech
• Pusher (The X-Files episode) § "Cerulean blue is a gentle breeze"
• List of colors
• Pigment
• Blue pigments

• A page on Cerulean Blue
• Cerulean blue at ColourLex