Cerulean


Cerulean, also spelled caerulean, is a shade of blue ranging between azure and a darker sky blue.
The first recorded use of cerulean as a colour name in English was in 1590. The word is derived from the Latin word , "dark blue, blue, or blue-green", which in turn probably derives from caerulum, diminutive of caelum, "heaven, sky".
"Cerulean blue" is the name of a pigment. The pigment was discovered in the late eighteenth century and designated as cerulean blue in the nineteenth century.

Cerulean blue pigment

In classical times, the word caerulum was used to describe blue pigments, particularly mixtures of copper and cobaltous oxides, like azurite and smalt. These early attempts to create sky blue colours were often less than satisfactory due to a limited saturation and the tendency to discolour in reaction with other pigments. See also Tekhelet.
The pigment Cerulean blue was discovered in 1789 by the Swiss chemist Albrecht Höpfner. Subsequently, there was a limited German production under the name of Cölinblau. It was in 1860 first marketed in the United Kingdom by colourman George Rowney, as "coeruleum". Other nineteenth century English pigment names included "ceruleum blue" and "corruleum blue".
Pigments through the ages shows a "Painted swatch of cerulean blue" that is representative of the actual cobalt stannate pigment. This colour swatch matches the colour shown in the colour box at right. See also painted swatch and crystals of cerulean blue at ColourLex.
The primary chemical constituent of the pigment is cobalt stannate. The precise hue of the pigment is dependent on a variable silicate component. The pigment is very expensive.
When the pigment cerulean blue was discovered, it became a useful addition to Prussian blue, cobalt blue and synthetic ultramarine which already had superseded the prior pigments.
It is particularly valuable for artistic painting of skies because of its hue, its permanence, and its opaqueness. 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.
, Summer's Day, 1879
Today, cobalt chromate is sometimes marketed under the cerulean blue name but is darker and greener than the cobalt stannate version. The chromate makes excellent turquoise colours and is identified by Rex Art and some other manufacturers as "cobalt turquoise".

Other colour variations

Pale cerulean

, in a press release, declared the pale hue of cerulean at right, which they call cerulean, as the "colour of the millennium".
The source of this colour is the "Pantone Textile Paper eXtended " colour list, colour #15-4020 TPX—Cerulean.

Cerulean (Crayola)

This bright tone of cerulean is the colour called cerulean by Crayola crayons.

Cerulean frost

At right is displayed the colour cerulean frost.
Cerulean frost is one of the colours in the special set of metallic coloured Crayola crayons called Silver Swirls, the colours of which were formulated by Crayola in 1990.

In nature

Literature