Transparent Cobalt Blue and Green

Transparent Cobalt Blue. Cobalt blue [1345-16-0] C.I. Pigment Blue 28 77346, is also produced as a transparent pigment by precipitating cobalt and then aluminum as hydroxides or carbonates from salt solutions using alkali. The hydroxides or carbonates are then filtered, washed, dried, and calcined at 1000°C [5.278]. It is important to carry out the precipitation with high dilution and to distribute the alkali uniformly throughout the entire reaction volume. 

Transparent cobalt blue pigments have the form of small tiles (primary particle size 20-100 nm, thickness ca. 5 nm, specific surface area (BET) ca. 100 m2/g). They are resistant to light and weather and are used in metallic paint, but are of little importance. 

Transparent Cobalt Green, Analogous to cobalt blue a transparent cobalt green spinel C.I. Pigment Green 19 77335 can be manufactured. 

The green as well as the blue transparent cobalt pigments are used as filter materials for cathode ray tubes (CRT) [5.279]. 

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