Metals and chemical knowledge in unexpected places: stained glass windows

This week I am diverting a little from my usual focus – I just found this too fascinating not to share it. So far, I’ve mainly concentrated on the use of metals in medicine and chemistry. Yet of course, metals were used in numerous other ways in the eighteenth century. There are the obvious applications if making tools and instruments, for money, jewellery, locksmithing, and cutlery. Metals were also essential in other arts and crafts, such as the creation of (coloured) glass. This may seem utterly artisanal, but the skills and knowledge involved were indeed relevant for academic chemists as well, as shows form Herman Boerhaave’s 1732 chemistry handbook.

In a section of the use of chemistry for the arts and crafts, he devotes over six pages to making glass, and how to colour it. Partly this makes sense, as a chemist was (and is) dependent on glass objects such as phials and bottles.

Glass retorts used in the chemical laboratory, from Boerhaave, Elementa Chemiae.

Glass retorts used in the chemical laboratory, from Boerhaave, Elementa Chemiae.

For example, Boerhaave explains that experiments have been made to aggravate glass with lead, but that these have failed so far as the addition of the lead tends to make glass brittle, rendering it unusable. Yet why would an academic chemist be interested in applications such as the creation of coloured glass? Boerhaave writes admiringly about the ‘Gouda glasses,’ the stained glass windows in the St Jan church in Gouda:

“There is also a […] kind of painting, which represents things on glass the most beuatiful yet transparent colours: the wonders of this art we see in great perfection in the windows of a church at Guada in Holland; which no modern performance can come up to. By means of this art they lay colours on the surface of the glass, which being baked by force of fire, their former lustre improved, and their substance diffused to a perfect transparency, penetrates the body of the glass, yet without passing a hair’s breadth beyond their assigned limits, or blending with the adjacent ones. I scarce know of any thing more curious and beautiful, or that contributes more to the ornament of churches, halls, and other buildings. The recovery of this art, now almost lost, is hardly to be expected, except from some chemist who should apply the discoveries of his art to this use.”[1]

The birth of Jesus, window 12 in the St Jan church in Gouda, made in 1564.

The birth of Jesus, window 12 in the St Jan church in Gouda, made in 1564.

Subsequently, Boerhaave lists other uses of glass, and the various methods to make it, and how to colour it with different metals. His admiration of the Gouda windows is one of the few insights he gave into his personal preferences outside his professional life. To understand this rare expression of emotion on a subject so different from his usual discourse, it is important to keep two things in mind. First, as convincingly argued by Knoeff in her 2002 book on Boerhaave, the man was deeply devout. Although the church windows at Gouda also contained more worldly, politically inspired images, the biblical representations in the impressive windows must have moved a religious man in a predominantly Protestant country, in which religious pictures -unlike religious symbols- in the public domain were quite rare.

Secondly, the Gouda church windows were and are among the great monuments in the Netherlands. For Boerhaave, who hardly travelled and whose farthest journey had been to Harderwijk, about one hundred kilometres from Leiden, these windows must have been one of the most beautiful monuments he saw in his life.

However, Boerhaave’s knowledge about and admiration for the craft of glass staining in general and for the Gouda windows in particular also confirms recent scholarship on the boundary nature of early modern chemical and technical knowledge and practices. Studying the use of materials in the early modern period is a route into understanding  mixed artisanal and learned practices, and reveals the existence of what Klein and Spary call ‘hybrid experts,’ men and women who combined artisanal and scholarly skills, terms, reasoning and explanations.[2] The hybrid expertise of people like Boerhaave and his contemporaries in turn can give us insights in issues such as discipline formation, and the epistemological and socio-economical developments preceding the industrial revolution.

        [1] Boerhaave, Herman. Elementa chemiae, quae anniversario labore docuit in publicis, privatisque scholis. 2 vols, vo.l. I, Leiden: Isaak Severinus, 1732, p. 180 cont.

[2] 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.

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