Caspian Blue - Blue in Science and Industry - Blue Pigments and Dyes

Blue Pigments and Dyes

Blue pigments were made from minerals, especially lapis lazuli and azurite (Cu₃(CO₃)₂(OH)₂). These minerals were crushed, ground into powder, and then mixed with a quick-drying binding agent, such as egg yolk (tempera painting); or with a slow-drying oil, such as linseed oil, for oil painting. To make blue stained glass, cobalt blue (cobalt(II) aluminate: CoAl₂O₄)pigment was mixed with the glass. Other common blue pigments made from minerals are ultramarine (Na_8-10Al₆Si₆O₂₄S_2-4), cerulean blue (primarily cobalt (II) stanate: Co₂SnO₄), and Prussian blue (milori blue: primarily Fe₇(CN)₁₈).

Natural dyes to colour cloth and tapestries were made from plants. Woad and true indigo were used to produce indigo dye used to colour fabrics blue or indigo. Since the 18th century, natural blue dyes have largely been replaced by synthetic dyes.

• Lapis lazuli, mined in Afghanistan for more than three thousand years, was used for jewellery and ornaments, and later was crushed and powdered and used as a pigment. The more it was ground, the lighter the blue colour became.

• Azurite, common in Europe and Asia, is produced by the weathering of copper ore deposits. It was crushed and powdered and used as a pigment from ancient times,

• Natural ultramarine, made by grinding and purifying lapis lazuli, was the finest available blue pigment in the Middle Ages and the Renaissance. It was extremely expensive, and in Italian Renaissance art, it was often reserved the robes of the Virgin Mary.

• Egyptian blue, the first artificial pigment, created in the third millennium BC in Ancient Egypt by grinding sand, copper and natron, and then heating them. It was often used in tomb paintings and funereal objects to protect the dead in their afterlife.

• Ground azurite was often in Renaissance used as a substitute for the much more expensive lapis lazuli. It made a rich blue, but was unstable and could turn dark green over time.

• Cerulean was created with copper and cobalt oxide, and used to make a sky blue colour. Like azurite, it could fade or turn green.

• Cobalt blue. Cobalt has been used for centuries to colour glass and ceramics; it was used to make the deep blue stained glass windows of Gothic cathedrals and Chinese porcelain beginning in the T'ang Dynasty. In 1799 a French chemist, Louis Jacques Thénard, made a synthetic cobalt blue pigment which became immensely popular with painters.

• Prussian blue was one of the first synthetic colours, created in Berlin in about 1706 as a substitute for lapis lazuli. It is also the blue used in blueprints.

• Indigo dye is made from the woad, Indigofera tinctoria, a plant common in Asia and Africa but little known in Europe until the 15th century. Its importation into Europe revolutionized the colour of clothing. It also became the colour used in blue denim and jeans. Nearly all indigo dye produced today is synthetic.

• Synthetic ultramarine pigment, invented in 1826, has the same chemical composition as natural ultramarine. It is more vivid than natural ultramarine because the particles are smaller and more uniform in size, and thus distribute the light more evenly.

• A new synthetic blue created in the 1930s is phtalocyanine, an intense colour widely used for making blue ink, dye, and pigment.