Watercolor prepared with Genuine Smalt inorganic mineral pigment, actually a cobalt-doped glass, i.e. potassium and cobalt silicate. The history of this pigmens goes many back many centuries: it likely was part of the blue color of some glasses of ancient Egypt. During the Middle Ages anyway artisans began to produce it to be used as a pigment, but it was mostly used during the 16th and 17th century. Its production involved the fusion of cobalt oxides (extracted from minerals) with sand and potash (potassium carbonate). The smalt is thus obtained: it's then ground and used as a pigment. It's an intense blue color tending to violet, with low tinting strength and really high transparency and lightfastness.
Colouring agent: Potassium cobaltous silicate