Cobalt Blue

Cobalt Blue (cobalt oxide of alumina, cobalt ultramarine, Thénard’s blue, royal blue, cerulean blue), blue pigment, consists primarily of cobalt aluminate CoAI₂O₄ and is obtained by glowing a mixture of phosphate of cobalt oxide with alumina hydrate or of alum with sulphate of cobalt. Cobalt blue prepared from cobalt oxide and alumina hydrate forms Leiden (Leithen) Blue, Vienna Blue. Cobalt blue has a reddish cast, but when prepared with the addition of zinc oxide it is true blue. It is similar to ultramarine, but much more stable, highly saturated, not fully opaque and appears violet in lamplight. It is used especially in glass and porcelain painting. It is denoted by U on blue colour works: FFU fine fine cobalt blue, MU medium cobalt blue and OU ordinary cobalt blue.

Single Pigment Colours

A small overview of cobalt blue (PB 28) single pigment colours suitable for miniatures, models, and dioramas.

• Cobalt Blue (PB 28, opaque), Liquitex 170
• Cobalt Blue light (PB 28, semi-opaque), PRIMAcryl 13.435
• Cobalt Blue, BLOCKX Artist Oils 652

Mixed Pigment Colours

• Cobalt Blue RAL 5013, glossy, Dupli-Color Acrylic Spray
• Cobalt Blue, translucent, Marabu Artist Acrylic 954

Source: Meyers Großes Konversations-Lexikon, 6. Auflage 1905–1909

Blue