Ruby Glass; (aka Cranberry Glass, Gold Ruby Glass or Rubino Oro as it is known by glass workers) is a red glass made by adding gold(III) oxide to molten glass. However, tin, in the form of stannous chloride, is sometimes added in tiny amounts as a reducing agent. The gold chloride is made by dissolving gold in a solution of nitric acid and hydrochloric acid (aqua regia). The glass is typically hand blown or molded.
The glass is used primarily in expensive decorations. Some historians believe it was first produced in the late Roman Empire. The craft was then lost and rediscovered in the 17th century by either Johann Kunckel in Potsdam or by the Florentine glass-maker Antonio Neri in Italy. But neither of them knew the mechanism which yielded the colour. Chemist and winner of the 1925 Nobel Prize in Chemistry, Richard Adolf Zsigmondy, was able to understand and explain that small colloids of gold were responsible for the red colour.
The most famous period of ruby glass production was in 19th century Britain during the Victorian Era, where it was frequently used for wine glasses, decanters, and finger bowls; and well known for its use in “Mary Gregory” glass which had a white enamel fired onto the glass in a design, usually of the romantic variety – how very apt for Valentine’s Day.