Spotlight on Cobalt Green
In 1780, the process for making a compound of cobalt and zinc was developed by Swedish chemist, Sven Rinmann. By exposing a mixture of cobalt and zinc to strong heat, which was then washed, the Cobalt Green pigment was ready to grind. Although available since 1835, Cobalt green pigment was not widely used until after 1860 when zinc oxide became more readily available. Arthur Church, the chemist and amateur painter, published Rinmann's process in his book, ‘The Chemistry of Paints and Painting.’ (London, 1901) He praised Cobalt Green as ‘chemically and artistically perfect.’
Cobalt Green provides an option for the painter to the more widely used Phthalo based greens or Chromium Oxide. A fast drier in oil, in water colour Cobalt Green has the characteristic of ‘granulating’ in washes, similar to Ultramarine.