Cobalt blue
Cobalt blue is a cool, slightly desaturated blue color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...

, historically made using cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

 salts of alumina. It is used in certain ceramics (historically, especially Chinese porcelain) and painting; the different cobalt pigment smalt
Smalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...

, based on silica, is more often used directly in tinted transparent glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

es. The pigment is extraordinarily stable.

Chemically, cobalt blue is a cobalt(II) oxide
Cobalt(II) oxide
Cobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder...

-aluminium oxide
Aluminium oxide
Aluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...

, or cobalt(II) aluminate, CoAl2O4. The compound is made by sintering
Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature...

 the stoichiometric mixture of finely ground CoO and Al2O3 (alumina) at 1200°C.

Cobalt blue in impure form had long been used in Chinese porcelain, but was independently discovered as a pure alumina-based pigment by Louis Jacques Thénard
Louis Jacques Thénard
Louis Jacques Thénard , was a French chemist.His father, a poor peasant, managed to have him educated at the academy of Sens, and sent him at the age of sixteen to study pharmacy in Paris. There he attended the lectures of Antoine François Fourcroy and Louis Nicolas Vauquelin...

, in 1802. Commercial production began in France in 1807. The first recorded use of cobalt blue as a color name in English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

 was in 1777. The leading world manufacturer of cobalt blue in the 19th century was Blaafarveværket
Blaafarveværket in Modum, Norway, founded by King Christian VII of Denmark-Norway in the 1770s, became the largest industrial company of the country in the mid-19th century. The works mined cobalt ore and manufactured by smelting blue cobalt glass and cobalt blue pigment...

 ("blue-color works," in Dano-Norwegian) in Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, led by Benjamin Wegner
Jacob Benjamin Wegner
Jacob Benjamin Wegner was a Prussian-born, Norwegian investor, industrialist, diplomat and landowner.-Biography:Jacob Benjamin Wegner was born in Königsberg in East Prussia. He was from a shipping family...

. Germany was also famous for production- especially the Blaufarbenwerke ("blue-color works," in German) of Schneeburg. The dye is not to be confused with Prussian blue
Prussian blue
Prussian blue is a dark blue pigment with the idealized formula Fe718. Another name for the color Prussian blue is Berlin blue or, in painting, Parisian blue. Turnbull's blue is the same substance but is made from different reagents....

, which is an intensely-blue pigment based on iron and cyanide, that contains no cobalt.

Cobalt blue in human culture

Art is the product or process of deliberately arranging items in a way that influences and affects one or more of the senses, emotions, and intellect....

  • John Varley
    John Varley (painter)
    John Varley was an English watercolour painter and astrologer, and a close friend of William Blake. They collaborated in 1819–1820 on the book Visionary Heads, written by Varley and illustrated by Blake...

     suggested cobalt blue as a good substitution for ultramarine
    Ultramarine is a blue pigment consisting primarily of a double silicate of aluminium and sodium with some sulfides or sulfates, and occurring in nature as a proximate component of lapis lazuli...

     blue for painting skies.
  • Maxfield Parrish
    Maxfield Parrish
    Maxfield Parrish was an American painter and illustrator active in the first half of the twentieth century. He is known for his distinctive saturated hues and idealized neo-classical imagery.-Life:...

    , famous partly for the intensity of his skyscapes, used cobalt blue, and cobalt blue is sometimes called Parrish blue as a result.
  • Cobalt blue was the primary blue pigment used in Chinese blue and white porcelain for centuries, beginning in the late 8th or early 9th century.

In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...

  • Because of its chemical stability in the presence of alkali, cobalt blue is used as a pigment in blue concrete
    Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...


  • The blue
    Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal...

     seen on many glassware pieces is cobalt blue, and it is used widely by artists in many other fields.
  • Cobalt glass
    Cobalt glass
    Cobalt glass is a deep blue colored glass prepared by adding cobalt compounds to the molten glass. It is appreciated for its attractive color. It is also used as an optical filter in flame tests to filter out the yellow flame caused by the contamination of sodium, and expand the ability to see...

     almost perfectly filters out the bright yellow emission of ionized sodium, common in most flames (as even the most trace amount of it is very overpowering).

Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...

  • "Cobalt Blue" is used as a filter used in ophthalmoscopes, and is used to illuminate the cornea of the eye following application of fluorescein dye
    Fluorescein is a synthetic organic compound available as a dark orange/red powder soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications....

     which is used to detect corneal ulcers and scratches.

  • Major League Soccer
    Major League Soccer
    Major League Soccer is a professional soccer league based in the United States and sanctioned by the United States Soccer Federation . The league is composed of 19 teams — 16 in the U.S. and 3 in Canada...

    's Kansas City Wizards
    Kansas City Wizards
    Sporting Kansas City is an American professional soccer club based in Kansas City, Kansas that competes in Major League Soccer , the top professional soccer league in the United States of America and Canada...

     have had cobalt blue as the secondary color of its home uniforms since 2008
    2008 Major League Soccer season
    The 2008 Major League Soccer season was the 13th season in league history. The season began on March 29 and ended with MLS Cup 2008, on November 23 at The Home Depot Center in Carson, California.-Changes from the 2007 season:...


  • Several countries, like the Netherlands
    The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

     and Romania
    Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...

    , have cobalt blue as one of three shades of their tricolour
    A tricolour is a flag or banner more-or-less equally divided into three bands of differing colours...



Cobalt blue is toxic when inhaled or ingested. Potters who fail to take adequate precautions when using cobalt blue may succumb to cobalt poisoning
Cobalt poisoning
Cobalt poisoning is intoxication caused by excessive levels of cobalt in the body. Cobalt is an essential element for health in animals in minute amounts as a component of Vitamin B12. A deficiency of cobalt, which is very rare, is also potentially lethal, leading to pernicious anemia. However in...

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