Ultramarine natural
Composition and Properties of Ultramarine natural
Ultramarine is a complex sodium silicate containing sulfur and aluminum with the chemical formula Na7Al6Si6O24S3. The intense and unique blue color is caused by the unpaired electron in the sulfur radical anions S3-.It is chemically stable under normal conditions and is also resistant to high temperatures. The pigment is also resistant to alkaline solutions and can thus be employed in fresco, it is, however, unstable even in dilute acids and decomposes to yield hydrogen sulfide.There are no known incompatibilities with other pigments.
Names
Azzurrum ultramarinum, lapis lazuli ultramarinePB 29, CI 77007From Medieval Latin ultramarinus, literally “beyond the sea,” from ultra– “beyond” + marinus “of the sea”. Said to be so called because the mineral was imported from Asia.From WordFinder
Preparation of Ultramarine natural
The source of natural ultramarine is the mineral lapis lazuli which is a fairly complex mixture of limestone, silicate minerals and also pyrite containing the mineral lazurite which is the actual source of ultramarine. The image below clearly shows the different constituents of the mineral: white limestone and quartz, yellow pyrite and blue lazurite.The best known historical method for preparation of high-quality ultramarine from Lapis lazuli was described by the Italian painter Cennino Cennini in his well-known handbook for painters “Libro dell’arte o trattato della pittura” (1).
History of Use
The following graph gives the frequency of its use in the paintings of the Schack Collection in the Bavarian State Art Collections in Munich (1).References(1) Kühn, H., Die Pigmente in den Gemälden der Schack-Galerie, in: Bayerische Staatsgemäldesammlungen (Ed.) Schack-Galerie (Gemäldekataloge Bd. II), München 1969.
