Category Archives: Experimentation

The “Gentle Heat” of Boerhaave’s Little Furnace

By Ruben Verwaal and Marieke Hendriksen

Ruben Verwaal is curator of the historical collections at Erasmus Medical Centre, Rotterdam, and at the Museum for Communication in The Hague. He obtained his PhD in June 2018 with a thesis on the role of bodily fluids in eighteenth-century chemistry. Marieke Hendriksen is a postdoctoral researcher on the Artechne Project at Utrecht University and a long-time contributor to The Recipes Project. She specializes in the material culture of science and art in the long eighteenth century. Ruben and Marieke share an obsession with an eighteenth-century object that has since disappeared: a small chemical furnace.

With the introduction of chemistry into the university curriculum in the late seventeenth century, new practical needs arose for students  such as being able to perform experiments. Would it be possible to build a chemical furnace that provides a gentle heat, yields no smoke, and is safe for students to use? Herman Boerhaave (1668–1738) believed he found the perfect solution in, what came to be called, Boerhaave’s little furnace.

Portrait of Herman Boerhaave by Cornelis Troost, c. 1730.

Boerhaave was professor of medicine, botany and chemistry at Leiden University in the early 18th century.[1] Instead of starting with the most difficult experiments with metals and minerals, he was convinced that students were better off when they learned the techniques of through simpler processes, such as distilling leaves and flowers, and fermenting bodily fluids. But most chemical laboratories were equipped with elaborate devices too complicated for freshmen students, who in the eighteenth century could be as young as fourteen. Moreover, the brick-build furnaces were designed to create high temperatures, in which small and delicate materials like rosemary leaves would burn instantly.[2] Boerhaave hence needed a device that was low-cost, user-friendly, and would provide a gentle heat.

The plan for the oven, • H. Boerhaave, Elementa Chemiae, Quae Anniversario Labore Docuit in Publicis, Privatisque Scholis, (Leiden 1732).

A small wooden oven was the answer. Boerhaave claimed he had designed this type of furnace when he himself was studying chemistry in the 1690s. He opened the chapter on instruments in his chemistry textbook with the words: “I shall begin with my simplest furnace; which I invented forty years ago, when I practiced chemistry in no large study, where there was only one little chimney, and where I required several furnaces at once.”[3]

Woman at the Virginal and stove under her feet, by Jan Miense Molenaer, 1630-1640. Rijksmuseum, Amsterdam.

This kind of device was probably inspired by ordinary foot stoves. These little stoves, also known as foot warmers, were very popular in the Dutch Republic. Coming in a wide variety of shapes (square, octagonal, cylinder), these stoves often feature in books and paintings. Filled with glowing coals or peat, women placed the little stoves under their robes or blankets to keep warm.[4] Many foot stoves were equipped with a wire bail handle for lifting and easy transportation. Such stoves were used in carriages, sleighs, at home and in church to keep one’s feet warm. This ordinary foot warmer got new applications too, namely as tea and coffee stove,   and we suspect it was the model for the ‘simplest furnace’ in the Leiden chemical laboratory.

Woman carrying a little stove, Harmen ter Borch, 1648–1677. Rijksmuseum, Amsterdam.

The gentle heat produced by Boerhaave’s small oven proved very useful in performing all kinds of chemical experiments. Take rosemary, for example, the evergreen aromatic shrub. Distilled atop a “violent fire”, it would have been turned to flame, smoke, and ashes. But when rosemary instead was distilled at “summer-heat” (approx. 85º F), the mild operation would instead reveal the most volatile, fragrant and aromatic part of the plant ordinarily exhaled in summer. The same process could be applied to Angelica, basil, and all other aromatic plants.

Students in the Leiden laboratory, in Herman Boerhaave, Institutiones et experimenta chemiae (‘Paris’, 1724). Ghent University Library.

Boerhaave, in other words, attributed the success of his device to one’s control over gentle heat. Whenever the wooden oven was filled with hot pieces of coal or Dutch turf that was no longer smoking, it established a constant and moderate heat that could be kept up to 24 hours. As such, the instrument was perfect for students to perform all kinds of heating processes and distillations. In fact, he was so excited about this apparatus, that he claimed that “I believe eggs may be hatched by it”.[5]

Was Boerhaave’s little furnace really that user-friendly and effective as he claimed it was? We checked it out by recreating Boerhaave’s stove and performing experiments with it. Check out our next blog to entry to find out whether we succeeded!

Creating an oven from two old stoves… to be continued!

References:

[1] More on Boerhaave, see Marieke Hendriksen, “Boerhaave’s Mineral Chemistry and Its Influence on Eighteenth-Century Pharmacy in the Netherlands and England”, Ambix(2018) and Ruben Verwaal, “The Nature of Blood: Debating Haematology and Blood Chemistry in the Eighteenth-Century Dutch Republic”, Early Science and Medicine(2017).

[2] Boerhaave, Elementa Chemiae (Leiden:  Isaac Severinus, 1732), vol 2, experiment 1.

[3] Ibid., vol 1.

[4] Le Francq van Berkhey,Natuurlyke historie van Holland (Amsterdam: Yntema and Tieboel, 1769–1778), vol. 3, 706-707, 1200.

[5] Boerhaave, Elementa Chemiae, vol 1.

HEAT! A Recipes Project Thematic Series

Astronomy- the Earth and the sun during summer in the Northern hemisphere. Wellcome Collection.

As humans, we want to control heat. We want to create heat, temper or even extinguish it, depending on context and purpose. We have a very limited temperature range at which we are comfortable (some microbes and bacteria can survive temperatures as low as -20C and as high as 130C), so we spend an incredible amount of time managing heat, whether it is our body temperature or that of our homes, offices, laboratories, cars, or food.

When we started planning this series of blog posts in early May, we could not have suspected how appropriate the theme would feel by now. While much of northwestern Europe has not seen rain in weeks and is sighing under a heatwave with temperatures rising to 37C/98F, we have fled to airconditioned spaces to edit the posts. Climate-wise, heat is seasonal in these regions, but it has always played an important role in recipes year-round, all around the world, from antiquity to the present day, in fields as diverse as alchemy, chemistry, art, cooking, medicine, and personal grooming.

The common denominators of heat in all these realms are that it is either internal – emanating from the human body – or external, naturally occurring from the sun, thunder, or lava, or man-made through friction or fire. In the posts in this series, we will see a wide variety of attempts to control these different kinds of heat through recipes and instructions.

Managing natural heat: Venice turpentine is a thick paste (aka sticky mess) at room temperature, but becomes fluid around 25C, and nicely mixes into the rest of the varnish ingredients when left out in the sun. Photo: Marieke Hendriksen

Some of our authors recreate such attempts by reconstructing experiments outlined in historical art technical and chemical sources. Indra Kneepkens recounts how she discovered through reconstruction research that sometimes for a recipe to make sense, it should not only be followed to the letter, but also be read between the lines. Ruben Verwaal and Marieke Hendriksen use their experiments with two reconstructions of small chemical ovens to reflect on the role of experimental heat in the development of theories on the nature of life in the eighteenth century. Working in a similar vein but with culinary recipes, Marissa Nicosia, from Cooking the Archive, examines the problem of heat control in her recipe recreation adventures, outlining the challenges of translating cooking instructions meant for the early modern hearth to the modern gas stove.

The four elements, four qualities, four humours, four seasons, and four ages of man. Airbrush by Lois Hague, 1991. Wellcome Collection.

Other authors in the series took our invitation as an opportunity to investigate heat in medical theories across time and place. Aileen Das kicks off this series by arguing that heat occupied a central place in ancient Greek, Roman and medieval Islamicate theories about the human body and its care. Taking on the smelly problem of perspiration and body odor, Cari Casteel reminds us that this issue is as old as mankind and offers several remedies from Roman authors.  Catherine Rider, on the other hand, examines notions of heat in fertility remedies in medieval England, noting that, whilst popular, heat-based treatments (to either increase or reduce heat in the body) were not the only kind of fertility aid available to English couples. The series concludes with two posts focused on fever and disease. Writing on in Late Imperial China, Marta Hanson introduces us to ideas of fever in Chinese medicine. Finally, Nukhet Varlik turns our attention to the ambiguities inherent in early modern taxonomies of infection diseases, exploring fever as a symptom and as a disease category.

We’ve had a great time editing this series – hope you enjoy reading the posts wherever you are. Happy summer and stay cool!

Marieke Hendriksen and Elaine Leong

P.s. We were so inspired by our contributors’ posts that we’ve decided to dedicate the December issue to (you guessed it) COLD!. If you’re interested in joining the conversation, send a short pitch to recipes@mpiwg-berlin.mpg.de.

Counting on the body: Reflections on Numeracy in Indian dyeing practices

By Annapurna Mamidipudi

‘I don’t know how to read, but I can count’ said Salim, ‘I was not much for school, my father put me on an old tractor when I was 12, and told me to go around in circles, till I had learned to drive’. Salim was a 20 something driver, the same age as me, when I met him in 1990. I –along with a few other socially minded engineers – was trying to decipher the recipes from a century old colonial account of dyeing using natural materials, and he was hired to drive me around the weaver villages we were visiting in rural Andhra Pradesh in South India.  The idea was to use these recipes to bring natural dyeing practices lost over the last century back into the practice of craftspeople, in order to enter newly emerging green markets and support their livelihoods.

‘Keep the temperature around 70 degrees’ specifies the recipe. Yes, I could measure the temperature and tell when it was 70 degrees; but how to maintain a constant one? Salim smoked incessantly, yet he could blow on an open wood fire under the dyebath to keep it at a steady 70 degrees for as long as it took to extract the colour –whether yellow, brown or red. I measured and jotted down notes from his experiments, attempting to standardise a recipe that would provide fast colour across the different dyehouses, in the different villages where craftspeople were being trained to re learn natural dyeing practices. But this was an important first lesson about the material life of numbers in dyeing –they came attached with fires, smoke, dye baths, and always required a willing body to maintain them.

Indigo dyed yarn production in a weaver co-operative dyehouse © Moody Chetanand

So my first recipe:

Material needed:

For one kg. of yarn, take  15%  in weight in dyematerial Katha [Acasia Katechu]

Copper Sulphate: Take 10 % of weight of dye material

First measure out the quantity of dye material…….

‘Weavers don’t read, why would you want to write down a recipe in English?’ Salim interrupts, with some curiosity. The recipe is a formula, I explain, and it has to hold fast wherever we use it, and whoever uses it. It can be in any language, its the numbers and reproducibility that make it technical. ‘My car is technical, but I don’t need a manual’ he jokes, even as he measures out quantities out aloud for me to write into the journal we keep of all the dye experiments. After using the recipe on the field in a series of training workshops for weavers, he makes an observation. ‘Change the recipe standard to 4.5 kg, not one kg, if you want a stardardised recipe’. I reply patiently, if they learn to calculate quantities using the standard of 1 kg, they can multiply it by 4.5 or any number they chose, that’s the whole point of a recipe. ‘But they only use the 4.5 kg standard, or multiples of it, so if you write those down in the recipe, they don’t need to learn how to calculate percentages’. He is right, I realise, all across the world of Indian cotton handloom weaving, the general measure that applies across all dyehouses, is the weight of one box of cotton yarn, the ‘peti’, standardised across all thicknesses or counts of yarn. I change the recipe; we now formulate all recipes with 4.5 kg as the base. I need a calculator to figure out how much copper sulphate we need for the recipe for Katha, each time, meanwhile, Salim is measuring it out by hand. ‘Sometimes the quality is not so good, you have to add a bit more’. The weavers agree, accuracy is about the outcome of colour, not so much the weight of material as input.

Sample of jottings from a dyehouse in Peddapuram in Andhra Pradesh © Moody Chetanand

Almost ten years later, Salim is a master dyer, and well on his way to acquiring the skill of dyeing Indigo, one of the most difficult colours to master. He is successful in the market, and has trained more than a hundred artisan groups, forming a large network of dyers. I continue to be the documenter of recipes, now trying to author a small booklet of recipes in the four South Indian vernacular languages, for craftspeople learning natural dye colours. ‘You tell colour by smell, put away the notebook’, he says. Yet, in Salim’s pocket is a strip of paper that can measure the pH value of a solution; ‘Checking the Indigo vat with a pH paper helps me to get a general idea of how alkaline the vat is, before I start using my nose,’ he says. He is meticulous in checking the vats every morning and evening. ‘Yellappa is a master, [the 80 year old Indigo dyer who taught Salim] he doesn’t need the paper’, he says, a little enviously, ‘he can count on his nose to tell him when the vat is ready’. We decide to leave out the recipe for Indigo from the booklet, learning to tell colour and alkalinity by smell has to be learned from the master, not with recipes.

Salim setting up the Indigo vats in his dyehouse © Moody Chetanand

Ten years on, it is 2012, and I am theorising innovation in craft practices, as part of my PhD study –analysing the practices of dyers as socio-technical expertise. I am assailed by the smell of fermenting Indigo, as I enter the well functioning Indigo dyehouse for an interview with Salim the master dyer. Salim is a tad more portly, and is surrounded by a bevy of young men and women dyeing Indigo. ‘Come to learn Indigo dyeing?’ he asks with a smile. I take out my laptop, ‘put your hand in’ he says instead, ‘and turn the yarn 50 times’. I wet the hank of cotton yarn, and sit down amongst the other dyers. Unpractised as I am, I lose count after 37, but Salim tells me when I can stop, he can see when the colour is right.  Do you keep count? I ask the girl sitting next to me, curiously. ‘I used to’ she says, ‘now my body knows how long it takes, so the numbers disappear from my mind’.

Indigo dyeing: Dyehouse of Salim © Moody Chetanand

I reflect later, on how to write the recipe for Salim’s Indigo, and who to write it for. The underlying chemical principles of the traditional fermentation Indigo vat have been written up extensively by scholars and scientists. The aim of my own analysis was to establish that Salim like many other master dyers before and after him has indeed mastered the principles of Indigo dyeing. How does one establish that, without explicating his knowledge in scientific terms? Yet, even if I were to explicate such a recipe, Salim himself would not use it. Rather, he engages his material knowledge of Indigo as he problem solves, or sets up a new vat, or uses new materials to bring forth a resplendent blue time after time.

Where then does the knowledge of the underlying principle reside in his practice? I do not yet have an answer. All I can speculate is that the knowledge of the principles governing Indigo are known by Salim much like the numbers themselves are known in the dyeing: when dyers learn to count on their bodies, the numbers on the piece of paper disappear. Much like a weft thread woven through the warp, sometimes visible on the surface of the fabric, and at other times stabilised below the threads, Salim’s knowledge too is always present, sometimes visible and enumerable, and at other times invisible and embodied.


Annapurna Mamidipudi was trained as an engineer in electronics and communications, in Manipal, in South India. She had set up and worked for over 15 years in an NGO that supported vulnerable craft livelihoods where before completing her doctoral thesis titled “Towards a theory of innovation for handloom weaving in India” in the University of Maastricht in 2016. She is currently a visiting post doctoral fellow at the Max Planck Institute for the History of Science. She is a member of the NGO Timbaktu Collective’s executive committee, which works in the drought prone district of Anantapur in Andhra Pradesh to support women farmers and trustee of the Handloom Futures Trust, in Hyderabad.

Books of Secrets

By Mandy Aftel

From Fragrant:The Secret Life of Scent by Mandy Aftel

Alession Piemontese Frontispiece

In the early sixteenth century, a new kind of book appeared in Europe: Books of Secrets were popular compendiums that professed to divulge to the reader the secrets of nature, culled from ancient sources of knowledge and wisdom. The most famous was The Secrets of Alexis of Piedmont, the pseudonym of an Italian physician and alchemist. More than seventy editions were published in at least seven languages, including my personal copy of the 1595 English edition. A third of the book was taken up with formulas that were not culinary but medicinal, remedies for common ailments. There was a chapter of recipes for perfumes and other scented ingredients—lotions, soaps, and body powders. And it wasn’t only the culinary and perfume recipes that called for spices and natural essences. There was a mouthwash of benzoin, cinnamon, rosemary, and myrrh, for example.[i]

These books’ closest descendant in the modern world is the cookbook. But the very idea of a cookbook is a recent one. To the pre-modern mind, there was no clear distinction between food and medicine and craft, the domestic and healing and creative arts. Substances derived from plants and animals and minerals were “simples”—building blocks that could be combined to form different compounds. “Pharmacists had to know how to grind up mixtures of simples according to medical instructions or their own ingenuity,” writes Paul Freedman in Out of the East. “Pounding and grinding together these aromatic products was a tedious task and became a symbol of the art and labor of the medical or culinary expert in spices, the cook and the pharmacist.”

When I discovered the Books of Secrets, I was smitten not only by their wealth of useful knowledge but by their charm. Their primordial scrambling of appetites and arts mirrored the synesthetic nature of the senses. Here home remedies mingled with folk wisdom, traditional knowledge with family lore. They combined the seemingly contradictory strands of the practical and the mystical in a way that reminded me of perfume, which—for all the formulas generated in all the labs in all the fragrance houses—can never be reduced to a science. Indeed, herbs, flowers, and spices played a great role in the arts they covered, and so the books focused on the same ingredients that are used to create natural perfumes.

I’d reveled in the same promiscuous muddling of material in my library of antique perfume books, in which fragrance recipes rubbed shoulders with alchemy, folk remedies, and precursor versions of aromatherapy. But when I tried to use the recipes in a straightforward way—as if from a cookbook, I discovered something interesting.

I’d always thought, in the back of my mind, that if I ran out of ideas for new perfumes, I could use the recipes in these books to replicate the perfumes that used to be made—though I had not quite figured out how I would find, or afford, the copious amounts of musk and ambergris so many of the recipes called for. One day I decided to put that idea to the test and start making the perfumes in some of my old recipe books.

Handwritten Formula Book from 1838

Many of the formulas were for what were known as soliflors, the attempt to replicate the aroma of a delicate flower that couldn’t be scent-harvested, like lily of the valley or violet; they seemed to rely heavily on bitter almond, which smells like cherries, to convey the nuance of flowers. When I made a couple of the perfumes, however, they struck me as decidedly “old lady” and uninteresting. Moreover, as I combed through the books, giving the recipes a closer look, I realized that the recipes had frequently been copied from one book to another. Over time, presumably by being carelessly recopied by scribes who didn’t understand the processes behind the words they were transcribing, many of the recipes had become garbled in places, or completely unintelligible. None of this stopped me from regarding these antique books as important links to a remote and rich past, initiating me into the mysteries of antiquity. In fact, I realized that their true genius lay not in their formulas but in the world they conveyed, a lost world of eccentric personalities consumed with the passion for travel to uncharted places, in search of undiscovered treasures and exotic substances. And the most important “secret” they contained was an alternate way of looking at the world—an aura of romance, sensuality, adventure and creativity.

Perfumers Notebook 1876

As for the recipes, they taught me something too—not how to replicate the perfumes of the past, but how to regard the process of making things and passing on knowledge about that process. The recipes in these books had the patina of having been forged in a crucible of trial and error by real-life practitioners who were passing on their hard-won knowledge to like-minded artisans. But recipes, even faithfully copied, cannot convey the deeply personal, idiosyncratic processes out of which they were distilled. “Recipes collapse lived experience into a series of mechanical acts that, once parsed, anyone can follow,” Eamon observes. “While a ‘secret’ is someone’s private property or the property of a group, a recipe doesn’t belong to anyone. Once it is published, someone else appropriates it, uses it, varies it, and then passes it on. At each stop it gains something or loses something, is improved upon or degraded, and is changed to fit new needs and circumstances. Recipes are built upon the belief that somewhere at the beginning of the chain there is someone who does not use them.”[ii]

Inherent in the Books of Secrets were attitudes and beliefs that grew out of the medieval imagination and resonated deeply with my work as an artisan perfumer. They reflected a belief in “Maker’s knowledge” (verum factum), which means that to know something means knowing how to make it. Such expertise cannot be acquired from someone else’s experience, but must be accrued by handling, experimenting with, and learning from the materials themselves. The search for how to do something was an essential part of the process, and it even had a name: venatio, “the hunt,” which referred to the hunt after the secrets of nature. Venatio was exactly what I experienced when I was searching for the lost knowledge of natural perfumery.


Mandy Aftel is an artisan perfumer who has published on scent and flavour. She also has a small museum, The Aftel Archive of Curious Scents. (Details here.) The above excerpt is from her award-winning book, Fragrant:The Secret Life of Scent (Penguin, 2014). You can purchase her books here.