Rublev Colours Dry Pigments - Series 5 Cobalt Chromite Blue is a high-performance blue-green spinel pigment designed for maximum durability in both studio and industrial-style applications. Made from cobalt chromite blue-green spinel (Co(Al,Cr)2O4) and produced by solid-state reactions at very high temperature, this deep blue-green powder is lightfast, chemically inert, and highly resistant to acids, alkalis, heat, and weather.

Known as Pigment Blue 36 (PB 36), Cobalt Chromite Blue was originally developed for colouring demanding materials such as concrete, stucco, and grout, but it is equally valued by artists for paint making where permanence and stability are non-negotiable. It is compatible with a wide range of binders and can also be used with ceramic bodies and low-zinc glazes, making it a versatile choice for makers who work across painting, coatings, and ceramics.

A major advantage of this spinel pigment is ease of processing: it is easily dispersed and typically does not require grinding, allowing thorough dispersion with standard mixing equipment. In water-based systems it is semi-transparent with moderate tinting strength and may dry lighter and less saturated. In watercolour it can naturally flocculate, producing a desirable granulated, textured look.

Key specs

• Colour Index: PB 36 (77343)

• Pigment type: Synthetic inorganic

• Chemical formula: Co(Al,Cr)2O4 (cobalt chromite blue-green spinel)

• ASTM lightfastness: I (Acrylic, Oil, Watercolour)

• Mean particle size: 1.4 micrometers

• Heat stability: up to 800 C

• Oil absorption: 17 g oil / 100 g pigment

• Series: 5

• Size: 100g

Handling and safety
Not considered toxic in typical use, but as with all dry pigments avoid inhaling dust and avoid ingestion or prolonged skin contact. Conforms to ASTM D-4236.