James VI and I considered awarding a patent for making a 'blue azure' product for this purpose in Scotland in February 1609. In England and Scotland, smalt was added to laundry starch. However, its presence in Dieric Bouts' The Entombment from circa 1455 proves that it was used at least a century earlier. The invention of a European smalt process has traditionally been credited to a Bohemian glassmaker named Christoph Schürer, around 1540–1560. 1483), and in the frescos of Domenico Ghirlandaio (1449–1494). 1540), in Michael Pacher's painting 'The Early Fathers' Altar' (ca. For example, it is found in Hans Holbein the Younger's portrait of Sir William Butts (ca. Smalt, normally now discoloured, is common in European paintings from the 15th to 17th centuries. A large quantity of smalt was purchased for the decoration of the gallery of Francis I of France at Fontainebleau in 1536. A fragment of a mud painting in the ancient Tangut city of Khara-Khoto has been found to contain smalt, judged to be dated between the 11th and 13th centuries. Cobalt was used as a pigment in Central Asia from the 13th century. Samples of smalt in the Historical dye collection of the Technical University of Dresden, GermanyĬhinese porcelain used smalt glazes from the Tang dynasty onwards, though Chinese cobalt glass is found from the Zhou dynasty (1122–221 BC). However, when used in ceramics for underglaze decoration, it keeps its colour well, and is the main blue used in blue and white pottery from a wide range of dates and areas, including Chinese blue and white porcelain from the Yuan and Ming dynasties, Renaissance Italian maiolica and Delftware.

In paintings, smalt has a tendency to lose its color over a long period, and is little used today. Cobalt oxide smalt appears as a pigment in Egyptian pottery about five centuries later, and soon after in the Aegean region. The earliest known example of cobalt aluminate glass dates to a lump from about 2000 BC in ancient Mesopotamia, very possibly intended for use as a pigment it was rare until the modern era. Ming dish, with smalt blue decoration History Late Roman (circa 4th century AD) finger ring with blue glass intaglio of the figure of Victory

It is used in the distinctive blue bottles of Harvey's Bristol Cream sherry and Tŷ Nant mineral water. Cobalt aluminate, also known as ' cobalt blue', can be used in a similar way.Ĭobalt glass such as Bristol blue glass is appreciated for its attractive colour and is popular with collectors.

The long history of its manufacture and use has been described comprehensively. Moderately ground cobalt glass (potassium cobalt silicate)-called 'smalt'-has been historically important as a pigment in glassmaking, painting, pottery, for surface decoration of other types of glass and ceramics, and other media. Regulation cobalt blue olive oil tasting glass with watch glass cover Specialty tasting glasses made of cobalt glass are used by professional olive oil tasters to disguise the color of the oil being assessed to avoid bias in judging. Cobalt is a very intense colouring agent and very little is required to show a noticeable amount of colour.Ĭobalt glass plates are used as an optical filter in flame tests to filter out the undesired strong yellow light emitted by traces of sodium, and expand the ability to see violet and blue hues, similar to didymium glass. Deep blue glass colored with cobalt SmaltĬobalt glass-known as ' smalt' when ground as a pigment-is a deep blue coloured glass prepared by including a cobalt compound, typically cobalt oxide or cobalt carbonate, in a glass melt.

Cobalt glasses eyewear