Glass of the Alchemists: Lead Crystal–Gold Ruby, 1650-1750
In their well-known attempts to make gold, alchemists also provided the foundation for modern chemistry and material sciences.
Glass of the Alchemists explored Northern European glass of the Baroque period and examined the technical advances in glassmaking made by alchemists during that time. Their work provided essential knowledge about the purification of the raw materials used to make glass objects, and advanced the technology and construction of glassmaking furnaces. With these improvements, alchemy-inspired glassmakers were able to produce colorless crystal glass which came extremely close to the appearance of natural rock crystal, as well as stunning gold ruby glass vessels which look as if they were made from ruby %%stones%%. These achievements required the ability to select the right ingredients and an understanding of how to work with them, and these skills were learned in the laboratories of alchemists (then often known as “chymists”).
Glass of the Alchemists, curated by Dr. Dedo von Kerssenbrock-Krosigk, introduced some of the alchemists who changed the course of glassmaking, and presented innovative examples of 17th- and 18th-century glassware. The great innovators included the chymist Johann Rudolf Glauber (1604–1670), who spent part of his career in Amsterdam, where he experimented with glass chemistry. Glauber also created purple of Cassius, a solution of gold that paved the way for the production of gold ruby.
In the early 1670s, George Ravenscroft, a London businessman, employed glassmakers from the Continent to produce some of the first lead crystal, the appearance and working properties of which caused a revolution in the design and decoration of glass vessels. At about the same time, glassmakers in central Europe developed other formulas for colorless glass, which appealed to the cutters and engravers of objects that resembled rock crystal.
Johann Kunckel (1637?–1703) pursued a different line of inquiry. He studied in the alchemical library of the elector of Saxony in Dresden, and he later translated Antonio Neri’s L’Arte vetraria into German and added his own comments. By the mid-1680s, Kunckel, working in Potsdam at the glass factory of the elector of Brandenburg, was producing gold ruby by adding purple of Cassius to the batch. He was not the first glassmaker to produce gold ruby, but he was the first to use it to make large and complex vessels, which attracted attention and frequently were embellished with engraving or with mounts made of precious metal.
Glass of the Alchemists traced the history of lead crystal and gold ruby with 117 objects from 19 public and private collections in the United States and Europe. These objects included two of Ravenscroft’s glasses with the maker’s distinctive raven’s-head seal and four gold ruby vessels made at Potsdam between about 1685 and 1700, three of which are richly engraved, perhaps by Gottfried Spiller.
The exhibition ended with the Warrior Vase, a splendid example of colorless and gold ruby cameo glass made in China in the 18th or 19th century, and a curiosity: a gold ingot that Johann Friedrich Bottger produced in the presence of King Augustus II of Poland in 1713, claiming that he made it by transmuting base metal.
Dedo von Kerssenbrock-Krosigk, curator of Glass of the Alchemists, explains the significance of each of the major displays in the exhibition.