In the late 17th century, European glassmakers scored two major successes. In Bohemia, the British Isles, and Germany, they produced crystal glass vessels that resembled natural rock crystal. And in Brandenburg, Germany, they also manufactured red vessels—from gold ruby glass—that looked as if they had been carved out of colossal rubies.
The imitation of precious stones, especially ones as clear and colorless as rock crystal, had always been a goal of glassmaking. While paper-thin cristallo, a Venetian specialty during the Renaissance, had been praised for its perfection, it eventually gave way to this thick-walled Baroque crystal, which was richly decorated in relief. Interest shifted from glassblowing to the glass material itself, and to its decoration by cutting and engraving.
Both of these achievements—crystal and gold ruby glass—required knowledge and experience to select the right raw materials and to understand their interactions in the batch. A glassworks, with its ongoing production, was not a suitable environment for pure research. Instead, during this fruitful period, glassmakers reaped the benefits of experiments that were conducted elsewhere—in the laboratories of alchemists.
Alchemists are often considered to have been strange and mystical individuals who were obsessed with attempts to manufacture gold. Dutch paintings of the 17th century habitually portrayed alchemists as clueless adventurers who, having surrendered their last possessions in the pursuit of futile experiments, ended up on the streets as beggars. To be sure, alchemy was taken up by many people who were seeking to make a quick fortune, and their senseless endeavors and cheating discredited the entire field.
However, among these alchemists were pure researchers who introduced a science that was first known as “chymistry.” Chymists attempted to unlock the secrets of nature by simulating natural processes in laboratory conditions, and they offered theories to explain natural phenomena. While these advances have long been superseded by modern chemistry, many of the achievements of the alchemists attained as the world’s first material scientists retain their relevance today.
Johann Rudolf Glauber (1604–1670) was a pre-eminent chymist. He was born in a small town in the Spessart region of Germany, but spent a substantial period of his productive life in Amsterdam. There, he apparently used a furnace in the famous Rozengracht glasshouse for some of his experiments. His knowledge of raw materials and their purification was an essential part of the development and technology of glass in the Baroque era. Glauber can also be credited with the invention of purple of Cassius, a solution of gold that led to the production of gold ruby glass.
As far as we know, Glauber was not interested in making decorative glassware. But we can draw lines of influence from him to various glassmaking enterprises extending from the British Isles to China. While Glauber took no active part in their achievements, he provided a basis on which these ventures could flourish: through his own writings, and through the alchemists and glassmakers who came into contact with him.
About 1672, the Jacobspital glasshouse in Nijmegen, the Netherlands, halted production when the French laid siege to the town. Two of the owners of that glasshouse, Italians by birth, moved across the Channel. Johan van Barmont Baptista da Costa went to England, and Jor Odacio traveled to Ireland. Da Costa has been credited with introducing the lead glass for which the London businessman George Ravenscroft would receive a patent in 1674. A year later, Odacio was one of the patentees of a similar glass in Dublin. It thus appears that lead crystal had some roots in the Low Countries, despite the fact that no Netherland production of that glass has been confirmed. The Nijmegen glassworks maintained ties with the Rozengracht glasshouse, and it is therefore possible that Da Costa and Odacio knew about Glauber’s work.
A chief go-between for glassmaking developments in central Europe was Johann Daniel Crafft (1624–1697), who had worked as Glauber’s assistant for about 10 years. Crafft became a glassmaker himself, and introduced milk glass, produced with bone ash, to northern Europe.
Crafft, who had close contacts with leading scientists in Germany, was a principal source of glassmaking knowledge for various projects in southern Germany and in Vienna. He also visited southern Bohemia, and he may well have played a role in setting up the crystal glassworks in the city of Gratzen. After 1673, he worked with Johann Kunckel (1637?–1703) in Dresden.
Kunckel was a competent chymist, and he became a very successful glassmaker. He obtained a unique insight into alchemy by studying the prince of Saxony’s library of alchemical writings in Dresden, attempting to extract any kind of information that could be turned to profitable practice. He later examined Antonio Neri’s famous compilation of glass recipes, L’Arte Vetraria. By the time he published his German translation (with commentary) of this important resource for early modern glassmakers, he had started to establish a crystal glassworks for the prince of Brandenburg in Potsdam.
In Potsdam, in the mid-1680s, he successfully produced a deep red glass by adding a solution of gold to the batch. Kunckel admitted that he was not the true inventor of gold ruby glass, adding that “perhaps Glauber may have been behind [this].” While earlier attempts to make gold ruby resulted only in small samples, Kunckel was the first to use it to produce large and complex vessels.
From an alchemical viewpoint, the importance of gold ruby could not be overstated. Glauber thought it would lead to the philosopher’s stone, the “universal medicine” that was essential for transmuting base metals into gold and silver. Alchemical writings of old had described the stone as a red substance, and the making of a radiant red material in a complicated process that involved gold was deemed to be a major step forward in realizing Glauber’s dream.
In Berlin, in 1701, the alchemist Johann Friedrich Böttger (1682–1719) became famous for producing a gold “transmutation,” which involved the use of a “red tincture.” He left that city immediately, but was captured by the troops of the Saxon prince, who kept him imprisoned until 1714. During that time, Böttger was given every opportunity to conduct further research, in the hope that he would make gold in larger quantities. While this effort failed, he played a crucial role in the invention of European hard porcelain in 1707–1709.
About 1713, he also experimented with gold ruby glass, and on March 20, 1713, made two pieces of metal, one of gold and the other of silver, during an experiment in Dresden. The experiment was conducted in the presence of King Augustus II of Poland (prince Frederick Augustus I of Saxony), and the samples were thereafter part of the Saxon prince’s collections. His work may not have brought Böttger closer to discovering the secret of the philosopher’s stone, but it helped him to produce vessels consisting of colorless and gold ruby glass layers—the first time the art of casing glass had been practiced in Europe since the Roman period.
While Johann Daniel Crafft was serving as an adviser to the prince of Mainz, he must have met the Jesuit priest Christoph Diem (born 1636), an alchemist who became director of the prince’s laboratory. Diem helped to establish a glasshouse in Rechtenbach, and he may have influenced the Jesuit Kilian Stumpf (1655–1720), who studied theology in Mainz and became a member of the religious order’s mission to China in 1688. Stumpf, who organized the palace glassworks in Beijing and produced telescope lenses for the imperial observatories, displayed a thorough knowledge of glassmaking technology. Through his efforts, the alchemically inspired advances in European Baroque glassmaking reached the other side of the world in less than two decades.