Cobalt Zinc Blue Pigment, Size: 50 G Jar

SKU: NAP-417-1005
    Unit Price
    US$ 21.12
    US$ 21.12
    US$ 20.991%
    US$ 20.921%
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    Processing time
    Usually ships the next business day.
    Pigment type
    Inorganic, Synthetic

    Cobalt Zinc Blue (Colour Index Pigment Blue 72) is a modification of cobalt aluminate blue spinel pigments (Colour Index Pigment Blue 28). Cobalt aluminate blue pigments are the most durable blue pigments commercially available. They have excellent chemical and heat stability and can be used in chemically aggressive environments and exterior applications without fading.

    Pigment Names
    Common Names (pigment): English: cobalt zinc aluminate blue spinel
    French: spinelle bleu cobalt d'aluminate de zinc
    German: Kobalt Zinkaluminat blauen Spinell
    Italian: cobalto zinco alluminato blu spinello
    Spanish: cobalto espinela de aluminato de zinc azules
    Common Name Primary Mineral Source
    Cobalt Blue Cobalt Spinel England

    Pigment Information
    Color: Blue
    Pigment Classification: Synthetic Inorganic
    Colour Index: Pigment Blue 72 (77347)
    Chemical Name: Cobalt Zinc Aluminate (Spinel)
    Chemical Formula: (Co, Zn)2Al2O4
    CAS No.: 68186-87-8
    Series No.: 7
    ASTM Lightfastness
    Acrylic: I
    Oil: I
    Watercolor: I
    Physical Properties
    Particle Size (mean): 2 microns
    Density: 4.49 g/cm3
    Hardness: 5.0–5.6
    Refractive Index: 1.560–1.662
    Oil Absorption: 55 grams oil / 100 grams pigment
    Health and Safety No acute or known chronic health hazards are associated with this product's anticipated use (most chemicals are not thoroughly tested for chronic toxicity). Protect yourself against potentially unknown chronic hazards of this and other chemical products by keeping them out of your body. Do this by avoiding ingestion, excessive skin contact, and inhaling spraying mists, sanding dust, and vapors from heating. Conforms to ASTM D-4236.

    For a detailed explanation of the terms in the table above, please visit .

    Origin and History

    Cobalt aluminate is identified as the blue pigment on 30 polychromic shards of the 18th dynasty from Theben and Tell el Amarna. The spinel phase has a much lower cobalt/aluminum ratio than modern cobalt blue pigments. It probably contains nickel and zinc, which were found by x-ray spectroscopy. Cobalt salts were first identified in the eighteenth century. The earliest modern history of cobalt aluminate pigments commences with Leithner in Vienna, who appears to have discovered the basic process of calcining cobalt oxide and alumina (aluminum oxide) in 1775. Techniques for manufacturing cobalt blue, the chemically pure salt of cobalt and aluminum oxide, were developed in 1802.


    Cobalt blue is cobalt aluminate blue spinel (Pigment Blue 28 or PB 28) with the chemical structure CoAl2O4 of which there are three essential modifications (Pigment Blue 36:1, Pigment Blue 36, and Pigment Blue 72), in which parts of the cobalt are substituted either alone or in combination with chromium and zinc. These variations differ in their tinting strength and hue.

    Cobalt Blue Pigment Family
    Color Formula Color Index
    Cobalt aluminate blue spinel CoAl2O4 Pigment Blue 28
    Cobalt chromite blue-green spinel Co(Al,Cr)2O4 Pigment Blue 36
    Zinc cobalt chrome aluminum spinel (Zn, Co)(Cr, Al)2O4 Pigment Blue 36:1
    Cobalt zinc aluminate spinel (Co, Zn)Al2O4 Pigment Blue 72

    The basic cobalt blue color, Pigment Blue 28, is produced by high-temperature calcination of cobalt (II) oxide (CoO) and aluminum oxide (Al2O4). The variations are produced by the partial substitution of cobalt by chromium and zinc, either alone or in combination with each other. The result is a large variety of cobalt blue pigments that differ in their tinting strength or hues (reddish or greenish blue), depending on the exact chemical composition. The lighter-colored cobalt blue is prepared by adding zinc (II) oxide to the ingredients used for the basic pigment, forming Pigment Blue 72. Blue-green hues are produced by introducing chromium (III) oxide, partially replacing the aluminum (III) oxide in the basic cobalt blue, forming Pigment Blue 36.

    All of them form the crystalline modification of spinel during calcination. The spinels are a class of minerals that crystallize in the cubic (isometric) crystal system with the oxide anions arranged in a cubic close-packed lattice, and the cations occupy some or all of the octahedral and tetrahedral sites in the lattice. Spinel minerals form octahedral crystals that are usually twinned. They have an imperfect octahedral cleavage and conchoidal fracture. The hardness of spinel minerals is around 8 (chalk has a hardness of 2-3), specific gravity is 3.5-4.1, and it is transparent to opaque with a vitreous to dull luster.

    Permanence and Compatibility

    All cobalt blue pigments are chemically inert, absolutely insoluble, have good hiding power and excellent heat stability, and show excellent lightfastness and weather resistance.

    Water-Based Paint

    Cobalt blue is a semi-transparent pigment with moderate tinting strength in most water-based paint. When it dries, it appears lighter and less saturated. Although pigment particles are very fine, they flocculate, giving a grainy appearance in watercolor. Differences in how the pigment is ground and mixed lead to considerable differences in its performance.

    Oil-Based Paint

    Cobalt blue is a semi-transparent pigment with moderate tinting strength in oil-based paint. Differences in how the pigment is ground and mixed can lead to considerable differences in appearance.

    Oil Absorption and Grinding

    Cobalt blue absorbs a moderately high amount of oil, about 55 grams of linseed oil per 100 grams of pigment, to make a paste. It has been noted in some manuals that the pigment works better as a watercolor than it does in oil and is highly valued on that account among moist colors used by artists. Grinding it for artists' use in oil will require 35 percent dry pigment to 65 percent by weight of poppy seed or walnut oil, either of which some artists prefer to linseed oil. Cobalt blue has a greenish tone that is more or less reddish blue when viewed under incandescent light.


    Cobalt blue is not considered toxic; however, care should be used in handling the dry powder pigment to avoid inhaling the dust. All toxicological studies showed no signs of toxicity to humans or the environment.

    In animal studies, cobalt blue pigments did not display acute toxicity. No acute irritant effect was shown in tests to determine the acute irritation of the skin and mucous membranes. No statistically significant results were found in studies on rats to determine the carcinogenic potential. Soluble cobalt compounds, as well as cobalt metal, may have a sensitizing effect. However, none have been reported during the experience of many years of handling cobalt blue pigments.


    Since cobalt blue is inert and practically insoluble in water, it does not pose a hazard to the environment. The pigment can be removed mechanically from effluents. No dissolved heavy metals are released into the seepage water on controlled dump sites.

    For more information on handling pigments safely, please visit .

    Shipping specs
    50 lbs
    Shipping from
    This product is shipped from our supplier's warehouse in Willits, CA, United States
    Our guarantee
    This product is brand new and includes the manufacturer's warranty, so you can buy with confidence.
    A 25% handling charge is levied against all authorized returns except those due to our error. Unauthorized returns are subject to a 40% handling charge. Damages & defects must be reported to us within 14 days.
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