Mineral pigment (polysulphured sodium silico-aluminate) fairly stable even in acidic environments. In ancient times the natural form was used, Lapis Lazuli, a semi-precious stone, today used only for touch-ups. In 1830, Oltremare began to be produced with cheaper processes. Ultramarine is famous for its characteristic bright blue hue. The pigment is non-toxic, lightfast and suitable for most artistic techniques, but has limited resistance to alkalis and grays in acidic media. It is a medium covering pigment, with medium drying and which requires an average amount of thinner.
- Chemical description: Pigment Blue 29, C.I. 77007
- Color index: PB 29.77007
- Qualification: Watercolor, Acrylics, Lime / Fresco, Oil, Tempera
- Colors: Blue
- Form: powder
- Solubility in water: insoluble
- Formula: 2Na2Al2Si2O6 + NaS2 – Aluminum silicate and sodium sulphide.