Archaeology and early modern glassmaking recipes: The case of Oxford’s Old Ashmolean laboratory.

By Umberto Veronesi

Crystal blown bottle decorated with milk glass festoon (festoni di lattimo), c. 17th c., Venice.  Image courtesy of Wikimedia Commons.
Crystal blown bottle decorated with milk glass festoon (festoni di lattimo), c. 17th c., Venice. Image courtesy of Wikimedia Commons.

The product of human ingenuity, glass perfectly embodies the alchemical power to imitate nature by art and since the Bronze Age it has proved an incredibly hard substance to classify. Although glass only requires sand, salts and the action of fire, a quick look at any recipe collection will reveal that glassmakers have used a vast array of ingredients depending on what materials were available to them and on the physico-chemical characteristics desired. Colours and opacity were provided by the addition of the right metallic oxides, but even a perfectly colourless glass required specific reagents.[i]

Here, I am going to explore three 17th-century recipes for white enamels, what Venetians called lattimo. Enamels are glass pastes that could be coloured according to the need and then used as paint or to counterfeit gems. There are plenty of recipes out there, many are listed in Antonio Neri’ L’Arte Vetraria. However, in this post I am going to take my start from a different set of “primary” sources, namely the very crucibles used to manufacture white enamel at one of Europe’s leading chymical laboratories, the Old Ashmolean in Oxford. The residues found stuck to the walls of the vessels (Fig. 1) contain the chemical fingerprint of the ingredients used. The analysis of small cross-sections of such residues with a scanning electron microscope (SEM) are therefore a way to explore the recipes.

Figure 2. Crucible fragments analysed with glassmaking residues.
Figure 2. Crucible fragments analysed with glassmaking residues.

The chemical composition of the three residues shows both similarities and important differences. All of them have high levels of silica, corresponding to sand, the main component of glass. To melt silica a fondant is essential, and it needs to be added to the crucible. Here, two residues (B and C) bear the traces of a potassium-based fondant, probably saltpetre or even salt of tartar. Residue A has sodium oxide instead, which means that a different fondant was, pure soda most likely. Recipe-wise, this is the first relevant difference. Next, a reagent must also be added in order to render the glass paste white and opaque. A look at the microstructure of the residues (Fig. 2-4) helps identify what such reagents were and what different choices were made[ii].A (Fig. 2). The white aggregates visible in cross-section are the remnant of a mixture made of lead and tin calcined and then added to the crucible. This, together with somewhat large grains of sand, would produce the required colour and opacity.

Figure 3. SEM image of residue A showing dark sand grains and remains of lead-tin calx used as opacifying agent.
Figure 3. SEM image of residue A showing dark sand grains and remains of lead-tin calx used as opacifying agent.

B (Fig. 3). Here too crystals can be seen scattered throughout the glass and, like before, these are responsible for an opaque white enamel. However, these are made of tin oxide only, indicating that in this case the calx did not contain lead.

Figure 4. SEM image of residue B showing the tin oxide crystals as opacifying agent.
Figure 4. SEM image of residue B showing the tin oxide crystals as opacifying agent.

C (Fig. 4). There seems to be a third lattimo recipe being tested at the Old Ashmolean. This is more than a simple variant because it used a wholly different type of reagent, the antimony ore stibnite. The glass is indeed rich in antimony oxide while the microstructure reveals small white opacifying particles. These are a compound made of calcium and antimony that form when stibnite is added to the glass and heated. Such recipe is less common in technical writings, but it is reported in Christopher Merret’s commentary to Antonio Neri’s glassmaking treatise.[iii]

Figure 5. SEM image of residue C, showing the small opacifying crystals of calcium antimonate.
Figure 5. SEM image of residue C, showing the small opacifying crystals of calcium antimonate.

From this necessarily brief survey we can see that there is more than one way to make an opaque white glass paste. What is interesting is that such diversity happened at one of the leading chymical laboratories of its time, giving us an idea of the experimental nature of this enterprise. Making glasses was certainly a way of investigating nature, of looking at how transformations come about. At the same time, it was a way to test recipes for the industry. In this sense, artifacts can become a powerful tool for the history of recipes, another way to enter the arena of artisanal knowledge.

[i] Cable Michael 2001, p. 307.

[ii] Neri’s recipes for white enamel can be found in: Cable Michael. The world’s most famous book on glassmaking. The Art of glass by Antonio Neri, translated into English by Christopher Merrett (The Society of Glass Technology, 2001), Book 3.

[iii] For a general survey on glassmaking I suggest chapters from: Janssens Koen (Ed.). Modern Methods for Analysing Archaeological and Historical Glass, 2013.

Umberto Veronesi  is a Ph.D. candidate at the Institute of Archaeology, University College London. His dissertation entitled, “The archaeology of laboratory experiments and early chemistry: Oxford to Jamestown and back” focuses on exploring the practice of alchemy through the lenses of the archaeological materials coming from early chemical laboratories and uses scientific archaeology as a means to inform historical research and questions. Veronesi received his BA in Archaeology from the Sapeinza Universita di Roma in 2013, and his MSc Technology and Analysis of Archaeological Materials from the Institute of Archaeology, University College London in 2014.

Making Mr. Song’s Cheeses

By Miranda Brown

The subject of this post may strike readers as odd. The combination of “Chinese” and “cheese” brings little to mind: neither memorable textures, nor fragrant flavors. Nothing, not even a single name like Parmesan or cheddar. The reason for the dearth of associations is obvious enough. Cheese is largely absent from the Chinese diet, nowadays found only in the periphery of the Chinese world, in places like Yunnan and Mongolia, where it is regarded as ethnic food for Tibetans and other minorities.

Yet things were different several hundred years ago. Chinese gastronomes once waxed poetic about the taste and texture of cheese, professing their preference for it over elaborate delicacies. One poet, living in the thirteenth century, extolled the flavor of cheese, saying, “No need for fancy morsels when there is cheese!”[1] Another, living a century later, asserted the superiority of dairy to bean curd. “While this old fellow is content with his tofu,” he wrote, “The delight gotten from cheese is double.”[2]  These early foodies related recipes for manufacturing fresh, non-melting cheeses like paneer and the secrets for creating stretched curds like mozzarella.

Over the last several years, I have experimented with recipes for Chinese cheese, attempting to recapture the flavors and textures of centuries past. One recipe, for stretched-curd “milk threads,” proved tricky. Preserved in a 16thc-cookbook, Song’s Instructions for Preserving Life (Songshi yangsheng bu 宋氏養生部), the recipe can be summarized like this:

  1. Heat cow’s milk until hot.
  2. Pour in a souring agent (akin to diluted vinegar), dripping it into the milk gradually.
  3. Once a curd forms, collect it with a cotton wrap and shape into a disc.
  4. Take the curd and place inside of a pot of scalding water.
  5. In a separate vessel of scalding water, press it into the shape of a thin sheet of coarse silk.
  6. Place the curd onto a stick, rolling and pulling.
  7. Put the curd inside the scalding water in the pot, rolling and pulling three to five more times while in the water.
  8. Roll out the resulting thread, placing it on a rack to dry in the sun (oil can be added to make the product smoother).[3]

This recipe assumes a working knowledge of the cheesemaking process. Hence, the omission of precise measurements. Readers must know beforehand the quantities of milk or souring agent, and the temperature of the milk or scalding water. Needless to say, this presents a challenge to a modern cook who is unfamiliar with cheesemaking.

My first attempts to produce the cheese failed, even with un-homogenized milk. The resulting curds, small and grainy, refused to stretch after being immersed in hot water. I sought help from Youtube, watching videos of Indian housewives making kalari, a non-rennet string cheese that was similar to Song’s stretched curd in terms of ingredients (cow’s milk, vinegar, hot water). I noticed that when coagulating the milk, the home cooks would test the temperature of the milk with their fingers, stopping the heating process once they could no longer keep their fingers in the liquid, rather than waiting for the milk to come to a soft boil as one would when making ricotta or paneer. This made me think that control of temperature was key to success, something hinted by Song’s own directions: heat the milk until hot, not boiling. Still, my subsequent efforts to make the cheese failed despite the care taken during the initial curdling process. I wondered if the pasteurization process, which requires that the milk be heated to at least 165° Fahrenheit, had something to do with my lack of success.

My breakthrough came during a trip to California, where I was able to purchase raw or unpasteurized milk. I heated a quart of the raw milk gently until hot (110° F), then poured in a little diluted vinegar and shut off the heat, all the while continuously stirring the milk. Within minutes, the milk transformed into one large curd.

Figure 1: Raw milk coagulated with diluted vinegar. Image courtesy of the author.
Figure 1: Raw milk coagulated with diluted vinegar . Image courtesy of the author.

I removed the curd and heated a pot of water to simmering, and immersed the curd into the scalding water for a few moments, removing it from the pot and kneading, repeating the process three times. Voilà, an elastic curd that stretched easily.

Figure 2: The stretched curd with the author, made with a quart of milk. Image courtesy of the author.
Figure 2: The stretched curd with the author, made with a quart of milk. Image courtesy of the author.

Looking back at the experience with Chinese cheesemaking, I can say that the success of my experiment depended on a variety of factors: knowledge of arcane texts, watching other cheesemakers at work, and many failed experiments in the kitchen.

Miranda Brown teaches the history of Chinese science and food in the Department of Asian Languages and Cultures at the University of Michigan. Fascinated with recipes of all kinds, she is the author of the Art of Medicine in Early China (2015) and with Yang Yong, “The Wuwei Medical Manuscripts” (2017). She is currently writing a book about the premodern history of dairy in China.

[1] Zhu Xi  朱熹, Zhuzi wenji 朱子文集 (Taipei: Defu wenjiao jijinhui, 2000), 3/110.

[2] Yang, Lian 楊鐮 (chief editor), Quan Yuan shi 全元詩 (Beijing: Zhonghua shuju, 2013), 109.

[3] For a translation of the whole recipe, see Miranda Brown, “Mr. Song’s Cheeses, South China, 1368-1644.” Gastronomica: The Journal of Critical Food Studies (Forthcoming). 

Around the Table: Introductions

Editor’s Note: In this post, we’re delighted to welcome one of our new editors, Sarah Peters Kernan. Sarah completed her Ph.D. in History at the Ohio State University, with a dissertation entitled, “For all them that delight in Cookery”: The Production and Use of Cookery Books in England, 1300–1600, and she’s now working as an independent scholar. Here, Sarah describes some of the new ideas and activities she’ll be bringing to the RP. –AH

A doctor taking the pulse of a woman patient, seated at a table. Watercolour by Zhou Pei Qun, ca. 1890, courtesy of the Wellcome Collection.
A doctor taking the pulse of a woman patient, seated at a table. Watercolour by Zhou Pei Qun, ca. 1890, courtesy of the Wellcome Collection.

By Sarah Peters Kernan

As the Recipes Project begins a new year, we also begin a new series focused on our blog community. I recently joined the Recipes Project’s editorial team, and during my initial conversations with the other editors, I mentioned the many ways in which this blog has been important in my scholarly development. Throughout the final years of my graduate training and now, in my early career as an independent scholar, the Recipes Project has not only provided an outlet for writing and developing ideas, but a venue for connecting with other researchers and authors. I began meeting other contributors and readers at many conferences and seminars I have attended. While organizing conference sessions, I contacted potential presenters after perusing their posts on related topics. I have learned about new resources and methods from the diverse group of contributors. And, most importantly, the personal connections that I have made through the site have led to exciting conversations, ideas, projects, and even friendships. I value these ideas and relations all the more, because I have worked away from an academic home for a few years. I completed my dissertation hundreds of miles away from my university and am now working as an independent scholar. So despite being a virtual and international community, the Recipes Project has become a place to which I return often, frequently reading and occasionally contributing. My experiences appealed to the editors, and we decided to try strengthening this sense of community among our readership. Many of you have had similar connections because of the blog; it is now my job to facilitate even more of this.

Each month, I will highlight a different part of the Recipes Project community in the new series, Around the Table. The idea of any community joining together around a table is a powerful one; when we work together sorting through the issues surrounding historic recipes research, we can unearth so much more, as well as enjoy time with our colleagues. No matter what kind of table we encounter in our work and research—be it kitchen, craft, lab, or surgical—we can all learn from others around us. The editors know that our readers have many interests, careers, and uses for the blog. Hopefully this series serves as a catalyst for meeting other readers and contributors in person, collaborating on future projects, and confidently contacting others when you have questions about research, teaching, publishing, recipe re-creation, and more. Occasionally, I will revive the type of content found in past series, like First Monday Library Chats. In other posts, I will share conversations with curators, publishers, podcasters, and other scholars. You will find out what is going on in our fields at conferences and sharing in congratulations of our contributors with new jobs and completed degrees. As we all begin to know each other a bit more, it is my hope that you, too, will turn to the Recipes Project when you need to find a person, project, or idea.

In order to do all of this, I need your help! I encourage you to reach out to the Recipes Project through social media. We are active on Twitter and Facebook; let us all know when you have completed a degree, secured a new job, or won a major fellowship or award. Tell us about new job posts related to recipes, calls for papers, exhibition announcements, historical meal re-creations, and more. Please also share the conferences you are planning to attend. Just remember to use #historecipes so we can easily track your announcements; if you have shared your news or conferences, I may even contact you when working on certain posts in this series focused on topics like conference roundups and contributor accomplishments. You may, of course, also email the Recipes Project if you would prefer not to use social media. From time to time, the Recipes Project will use social media to organize informal cocktail hours and meetups at conferences, when we know many contributors and readers will be there. These informal gatherings may be infrequent for now, but it is our hope that these meetings will be a source of community and conviviality for those who can join us.

I look forward to hearing from you all and I am excited to share more about our wonderful Recipes Project community next month Around the Table!

Alchemical Recipes in the AlchemEast Project

By Matteo Martelli

What makes a recipe alchemical? Its inclusion in an alchemical treatise, one might suggest. Indeed, naïve as it may sound, such a simple answer opens an interesting perspective from which to look at the ancient alchemical tradition.

The earliest alchemical writings produced in Graeco-Roman Egypt (1st-2nd c. AD) include recipes that describe a variety of techniques for dyeing and manipulating the natural world – a spectrum of practices that goes far beyond simple attempts to produce gold out of ‘vile’ metals. Some of these techniques, ancient authors claim, were inherited from the Egyptian or Babylonian tradition; others reached Byzantium or Baghdad, often through translations of Greek texts into Syriac and Arabic.

This long-lasting tradition is as fluid as the boundaries of ancient alchemy. By mapping the specific practices and recipes detailed in each alchemical work, it will be possible to investigate changing ideas of alchemy over time as well as how these ideas responded to specific technological settings. On top of that, it will also be possible to follow the trajectories of single recipes which moved across works written in different languages or pertaining to different disciplines, such as medicine or natural philosophy.

Cinnabar (from the Monte Amiata mine, Tuscany) and metallic mercury

But let’s take an example from a set of texts that are being investigated in the framework of the ERC project AlchemEast, acronym for “Alchemy in the Making From ancient Babylonia via Graeco-Roman Egypt into the Byzantine, Syriac and Arabic traditions (1500 BCE – 1000 AD)”. Ancient natural philosophers and physicians recorded specific techniques for extracting mercury from cinnabar, its natural ore.

In his book On stones, Theophrastus, successor of Aristotle as head of the Lyceum, explained that it is possible to produce mercury by grinding cinnabar with vinegar in a copper mortar with a copper pestle.[1] The same procedure is described by Pliny the Elder, in book 32 of his Natural History, where the medical uses of minerals – mercury included! – are illustrated (NH 32.123).

Modern chemists noticed that these accounts actually described a mechano-chemical reaction between copper and cinnabar, a mercury sulfide: copper would react with sulfur, thus liberating free metallic mercury (chemically speaking, a redox reaction).[2] With the assistance of Lucia Maini and Massimo Gandolfi, two chemists of the AlchemEast team, we did replicate the technique with some adjustments. Rather than using a copper mortar – which proved to be very difficult to find in the shops that supply chemical labs today! – we decided to use a ceramic mortar where to grind pure cinnabar, acetic acid and copper powder.

Pure cinnabar, acetic acid and copper powder in a ceramic mortar

After grinding the mixture for a while, we were actually able to produce a layer of blackish powder (a mixture of metacinnabar and copper sulfide) on which a few drops of ‘dirty’ mercury were moving.

Mercury “floating” on a blackish layer of residues

The same procedure is described in ancient alchemical texts as well. The Graeco-Egyptian alchemist Zosimus of Panopolis (3rd-4th century AD) credits legendary figures, such as Maria the Jewess or Chymes, the eponymous hero of alchemy (called chymeia in Antiquity), with the use of similar technique for grinding cinnabar with vinegar in a lead or tin mortar.[3] Different metals were therefore used. In the lab, we actually tried to use tin rather than copper powder, thus obtaining a shiny mercury-tin amalgam.

Mercury-tin amalgam

We may preliminarily observe how this extraction technique was a kind of transdisciplinary know-how, shared by experts in different fields. A certain degree of variation is detectable in alchemical texts, which mention various metals. Moreover, ancient alchemists believed that mercury could be extracted from any metallic (or even mineral) body:  did this idea in some way depend on the empirical evidence they tried to conceptualize when treating cinnabar with a variety of metals?

This kind of questions are at the basis of the AlchemEast project, which explores ancient recipes from a double angle: as textual units that travelled over time and space; as invaluable windows on a wide spectrum of real practices and techniques. Textual criticism, replications, and historical investigations are critical keys to unlock ancient alchemical sources, from Babylonian tablets to Greek, Syriac and Arabic manuscripts.  This post is only a first, tentative attempt to illustrate how we applied this method, a preliminary result of our investigation, which, needless to say, is still “in the making.” We plan to continue keeping you posted in the following months.

[1] David E. Eichholz, Theophrastus, De Lapidibus, edited with Introduction, Translation and Commentary (Oxford: Clarendon Press, 1965), 81.
[2] Lazlo Takacs, “Quicksilver from Cinnabar. The First Documented Mechanochemical Reaction?” JOM. Journal of the Minerals, Metals and Materials Society, 52 (2000): 12-13.
[3] Marcelin Berthelot and Charles-Émile Ruelle, Collection des anciens alchimistes grecs (Paris: G. Steinheil, 1887-1888), vol. 2, 172. Part of Zosimus’ writings is only preserved in Syriac translation, where one finds further interesting details: cinnabar must be ground in the sun; copper filings are added to cinnabar and vinegar before grinding. The Syriac books of Zosimus will be published within the AlchemEast project.