Strange glass: Vitrium Antimonii

Pure antimony

Pure antimony

During my research fellowship at the Max Planck Institute for the History of Science in Berlin I studied the overlap (or lack thereof) of knowledge about making coloured and stained glass in artisanal versus medical circles in the eighteenth century Netherlands. Although it turned out that much of this knowledge was so tacit that it was never put down in writing properly, I found one remarkable boundary object, or rather a boundary material or ingredient: antimonial glass, or vitrium antimonii. Antimony is a lustrous grey metalloid, that occurs in nature as the sulfide mineral stibnite or antimonite. Roasted in an iron pot, it turns into antimony. Known since ancient times, the name is derived from the Greek anti-mono, meaning ‘not alone,’ because it does not occur in its pure form in nature. Because of its natural occurrence, colour and melting point, antimony was often confused with stibnite or lead. To add to the confusion the Dutch/German word ‘Spiesglas’ sometimes seems to refer to crude antimony, and at other times to antimonial glass. Moreover, the processes for creating glass of antimony and subsequently a red pigment from that glass, as described in Basil Valentine’s 1604 Triumphal Chariot of Antimony, are anything but straightforward.

Supposed antimonial glass (unverified modern reproduction)

Antimony is toxic for humans, and in early modern medicine it was sometimes employed in antimony cups, about which I have written before. Yet antimony could be transformed into other forms, and was thus used in both early modern visual arts and medicine. Although the exact origins of the recipes are unclear, by the seventeenth century, antimonial glass was generally understood as a clear, yellow or red vitreous substance made from calcined (powdered and roasted) antimony. This ‘glass’ was subsequently powdered and both used as a pigment in glass paints and solved in wine as a very strong emetic, a purge. The transformation from a silvery (mercurial) substance into something yellow or red (sulfurous) played a central role in alchemy, and was even associated with the secret to the Philosopher’s Stone, which could either transform all metals into gold or contained the secret to the universal panacea. This characteristic of silvery antimony transforming into yellow or red antimonial glass partly explains the popularity of such a toxic material.

According to Leiden professor of medicine, chemistry and botany Herman Boerhaave (1668-1737), the symbol for antimony:Antimony symbol “Denotes a chaos, χάος, world, or one thing which includes all: this is the character of antimony; wherein is found gold [the circle symbol], with plenty of an arsenical corrosive [the cross at the top].”About antimonial glass he remarked “The glass of antimony is almost mortally emetic; and when infused in wine, that is not considerably acid, it renders the liquor vomitive, without any great loss of its substance.”[1] Antimonial glass remained a popular ingredient for purges well into the nineteenth century, as shows from various apothecary and medical handbooks, as well as a pigment. Only with the rise of synthetic pigments, bacteriology and antisepsis does it seem to have disappeared from art and medicine.

Sample of supposed ‘Vitrum antimonii,’ probably eighteenth century. Source: Pharmaziemuseum Brixen, Italy.

With this disappearance, precise knowledge about the highly toxic process of creating antimonial glass disappeared as well. Fortunately there are people like history of chemistry professor Lawrence Principe, who reproduced many alchemical experiments and processes, amongst others that of making antimonial glass.[2] Principe discovered that antimonial glass can only be produced from stibnite ore containing some quartz, not from pure antimony – the quartz is essential for the vitrification of antimony. Without the quartz, the process results in dull grey lumps. A sample of supposed antimonial glass, probably from the eighteenth century, shows that there were apothecaries in Boerhaave’s time who already failed to understand this. Similarly, many apothecaries and artisans will have failed to produce a red pigment from glass of antimony, as Principe shows that it was not the antimony, but the residue of iron instruments that gave a preparation of antimonial glass and vinegar its red colour. It is this kind of reconstructive research that is essential to truly understand the complexities of early modern artisanal and medical knowledge.

[1] Herman Boerhaave, Elements of Chemistry, vol. 1, 68, and vol. 3, 322-3.

[2] Principe, Lawrence M. The Secrets of Alchemy. Chicago: University of Chicago Press, 2012, 90, 142-3.

A gemstone for every ailment?

Last week, I wrote about Boerhaave’s admiration for the stained glass windows in the St. John church in Gouda, and how his appreciation can be understood in the context of his life and times. Yet of course, the learned man did not write about stained glass windows in his chemistry book just because he thought they were beautiful. Always the scholar, Boerhaave had another reason to be interested in coloured glass, rooted in the medical and chemical theory of the day. In the Elements of Chemistry, Boerhaave described a number of ways to make coloured glass, but warns that this tends to result in artificial gems that, however lustrous, are more brittle than the real thing.[1]

Brooch, 1740-1750, Silver set with pastes (glass). Courtesy of the V&A (object nr. M.198-2007)

Brooch, 1740-1750, Silver set with pastes (glass). Courtesy of the V&A (object nr. M.198-2007)

Fake gemstones were used frequently in jewellery and fashion in the eighteenth century, but Boerhaave’s interest in them may still seem a bit curious. However, it is quite understandable in the light of a 1672 treatise by Robert Boyle, one of the alchemists Boerhaave admired. Boyle’s An essay, about the origine and virtue of gems argues that gem stones are infused with mineral and metal juices or particles when they are formed in the earth, either through great pressure, cold, or heat.[2]

These minerals and metals have medicinal qualities, and by grinding gemstones to powder, the medicinal qualities can be used in curative potions, creams, et cetera. But gemstones were rare, so it was beneficial for the early modern physician/chemist/natural philosopher to be able to create artificial gemstones with the same properties as real ones. As artificial gemstones are made mimicking the natural process, by infusing crystal with metals, it made perfect sense for Boyle, Boerhaave, and their contemporaries to use both natural and artificial gemstones as materia medica, basic medical materials.

Title page of Robert Boyle's 1673 'An essay, about the origine and virtue of gems.'

Title page of Robert Boyle’s 1672 ‘An essay, about the origine and virtue of gems.’

Artificial gemstones are an interesting case, as they shows that in the early modern period, the same artisanal and chemical knowledge and practices were relevant for experts in a number of fields, such as glassmaking, jewellery making, chemistry, pharmacy, and medicine. Often, these fields overlapped in more than one respect of course, and as I mentioned last week, studying the use of materials in the early modern period is a route into understanding the work of hybrid experts, people who combined artisanal and scholarly theories and practices.[3]

In the future, I hope to make the creation and use of gemstones in eighteenth-century chemistry and medicine one of the case studies in my research project. These initial findings raise questions about how involved university-trained chemists actually were in the making of materials such as artificial gemstones. Did they make them themselves in their laboratories? Or did they obtain them from glassmakers or apothecaries? And exactly how were the gemstones used in medicine and pharmacy? What were the various theories about their curative properties, and how were they transferred to the patient? Was the alchemical understanding of gemstones significantly different from the chemical understanding, or were alchemical theories and practices transferred into the chemistry and medicine of the late eighteenth century?

But first, summer, and on my program are a research trip to London, to look into a massive manuscript containing lecture notes taken by a student of the Leiden chemistry professor Hieronymus Gaub (1705-1780), presenting a paper at the huge and hugely exciting ICHSTM conference in Manchester, and delving into the work of Abraham Kaau Boerhaave (1715-1758), Boerhaave’s deaf nephew. I aim to keep the Medicine Chest filled with updates!

[1] Boerhaave, Herman. A new method of chemistry, 2 Vols, Vol. I, tranl. by Peter Shaw, London, 1741, p. 182-187.

[2] Boyle, Robert. An essay, about the origine and virtue of gems, London, 1673.

[3] Klein, Ursula, en Emma C. Spary. “Introduction: Why Materials?” In Materials and Expertise in Early Modern Europe. Between Market and Laboratory., Ursula Klein and Emma C. Spary (eds.), 1–23. Chicago and London: University of California Press, 2010, 1, 6.