Spinel Blue pigment

Spinel Blue pigment is a synthetic inorganic pigment powder, cobalt zinc aluminate blue spinel, (Co,Zn)Al₂O₄ (PB72): a zinc-modified, lighter relative of cobalt blue. It gives a soft mid blue, is lightfast and resistant to acids, alkalis and lime, and suits oil, acrylic, tempera, watercolor, gouache and fresco.

Key facts

• Color: soft mid blue with a slight violet tinge
• Pigment type: Synthetic inorganic pigment (cobalt zinc aluminate spinel)
• Colour Index: PB72 (C.I. 77347)
• Composition: cobalt zinc aluminate, (Co,Zn)Al₂O₄
• Origin: synthetic
• Also known as: blue spinel, cobalt zinc blue
• Opacity: semi-transparent
• Lightfastness: 8 of 8 on the Blue Wool Scale (supplier data)
• Chemical resistance: alkali 5/5, lime 5/5, acid 5/5 (supplier data, 5 = best)
• Suitable for: oil, acrylic, egg tempera, watercolor, gouache, fresco (lime)
• Packaging: 50 g jar

How to use

Mull it with a palette knife or muller into linseed oil, egg yolk, gum arabic or acrylic medium, and grind gently, as over-grinding dulls cobalt blues. Its tinting strength is moderate, so use it generously in mixtures; in oil it is semi-transparent and suits glazes. It is lime- and alkali-resistant and listed for fresco and silicate binders. Store dry in a closed jar.

About blue spinel

Spinel is the crystal structure shared by several high-temperature pigments, and cobalt blue (PB28) is the best known of them. Adding zinc oxide to the cobalt aluminate gives a lighter blue, which the Colour Index lists separately as PB72. Like other calcined cobalt spinels it is stable to light, heat and chemicals; our supplier gives heat resistance up to 1000 °C.

Safety

Contains cobalt compounds: may cause allergic skin or respiratory reactions; harmful if inhaled. Handle dry pigment with care: avoid breathing the dust and contact with eyes. Wear a dust mask (FFP2/N95) and gloves when working with the powder, work in a well-ventilated area and wipe up spills with a damp cloth. Do not eat, drink or smoke while working; wash your hands afterwards. Keep away from children and pets. For artistic and technical use only — not for cosmetics, food or tattoos.

FAQ

What is the difference between Spinel Blue and Cobalt blue?

Both are cobalt aluminate spinels. Spinel Blue (PB72) also contains zinc, which makes it lighter; our Cobalt blue (PB28) is a deeper, brighter blue.

Is Spinel Blue suitable for fresco?

Yes. Our supplier rates it 5 of 5 for lime and alkali resistance and lists it for fresco and silicate binders.