Colouring metals in the Far East

By Agnese Benzonelli

How far can someone go in the name of research? In my case quite a long way. For a month, I loosely taped tiny plates of metal to my hands and woke up every morning with green stains on them. I was investigating craft recipes employed in the far East since the fourteenth Century to create coloured metal and alloys used for beautiful small artefacts. Whereas Western taste preferred the natural colour and the polished lustre of metals, the Eastern preference was to use the process of chemical patination, where different chemicals react with the surface of copper and copper alloys to form new coloured compounds.

Fig.1: Left: a tsuba (handguard of Japanese sword) made of shakudo and gold; BM-TS244. Right: a Chinese gu-tong box; BM-1992,1109.2. Photos made by A. Benzonelli.

The Japanese created a whole class of coloured alloys, called irogane. They added small amounts of different elements to the copper and simmered it in a solution containing copper salts, alum, vinegar and other ingredients, to form coloured patinas on the surface. The most beautiful patina, shakudo, was made with copper and gold and achieved a deep blue-black colour. Combining a variety of alloy compositions and solution ingredients, they were able to create hues ranging from pale brown to black. Inlaying different irogane, gold, silver, and lacquers, they were able to create small artefacts and swords fittings with complex and visually impressive designs and patterns.

Fig.2: Picture of the 13 Japanese solutions created and tested taken from Japanese recipes reported in Eastern books.

Later on, Chinese craftspeople imported the technique from Japan, possibly through travellers or trying to copy the Japanese artefacts, and, from the Ming period (1368-1644), they used it to colour ink or tobacco boxes. In contrast to the Japanese irogane, the Chinese would patinate a gold-silver alloy only, which resulted in a dark colour similar to that of shakudo, which they called gu-tong. In both cases, the precious metal content was 1-3%, a larger amount would not affect the final patina colour.

There’s not a lot known about the two different recipes the Chinese craftsmen employed to produce their patinas. However, we do know that one process they utilised was similar to that used by the Japanese to produce the irogane,butwe have no precise recipes for the solutions. Another involved handling the metal until the perspiration from their hands corroded the surface.

Creating and play with metal colours has always fascinated me. Why using gold and silver to achieve that dark colour, instead of cheaper alternatives? What was the role of the different ingredients used in the recipes? Could sweat really be used as a patinating solution? Why did Japanese recipes tell not add precious metals to bronze (copper alloyed with tin) but only to pure copper? Could it be confirmed through scientific analysis that the technology was really transmitted from the Japanese to the Chinese culture? To find answers, I needed to conduct a systematic experimental research which could explain the reasons behind the technological choices of Japanese and Chinese craftsmen.

 I reproduced a series of alloys with tin, gold and silver, which I then patinated, following the recipes for shakudo and gu-tong from available texts. These are not numerous, as the recipes were mainly kept as secret and passed from father to son. We have city records, information sheets given by dealers and, in Japan, technical texts on metal working. I analysed the resulting patinas with techniques borrowed from modern material science, and used the experimental data as reference for the interpretation of historical patinated artefacts in museum collections.

I found that, for both the Japanese and Chinese recipes, the presence of gold in the alloy did, in fact, change the colour of the final patinas, which resulted in a better, more uniform and darker hue. I also noted how parameters such as the fine grade of surface polishing prior to the patination, the use of tin-free alloys, the selection of copper acetate as a main ingredient and the addition of vinegar are all processes and actions that led to a reduced patina growth. And as it turned out, sweat was indeed an effective patinating solution in the Chinese patination (as it can be noticed by the green corrosion products left on the hands), but the presence of gold in the alloy composition is nonetheless essential to obtain a dark hue, not achieved in gold-free alloys. Sweat is a slightly acidic solution, similar to that of used by Japanese craftsmen, essential to create a coloured copper oxide on the surface in just 48 hours of handling. Similarly, in both technologies cleaning of the alloy before or after the procedure suggested in Japanese texts and the abrasive action of the hands in the Chinese method are both similar and crucial steps in the patination process. I concluded from these findings that a dark patina was not the only feature that the craftsmen of both cultures had been striving for. They also seemed to be after a shiny appearance, given by the metallic lustre coming from the alloy.

Fig. 3: Alloys of different compositions patinated with Chinese patination.

In combining experimental and historical observations I gained an understanding of the intentions behind the technological choices made by the Japanese and Chinese artisans. My analysis confirmed the deliberate nature of these choices made to achieve dark and shiny blue-black colours otherwise impossible. This confirmed the importance of colour as a driver of these artisanal processes, and supports the idea that the knowledge was transmitted between the two cultures.

Was it worth in the end – the green hands and other discomforts suffered in the name of research? It was the first study to provide a scientific basis to our knowledge of the methods and choices made by those people, the ingredients they employed in making dark patinated artefacts, and contributed to our pool of knowledge of the artisanal methods and practices described in historical sources. So yes, it definitely was, and I would definitively do it again.

Tales from the Archives: Drinkable Gold for the King of Siam

In my first months of co-editing duties here at The Recipes Project, one of my many delights has been the opportunity to dig back in our archives to rediscover posts I’ve loved over the years, to see them with fresh eyes. As a historian of Japan, I’ve looked forward to exploring and expanding our content on Asia, especially in global exchange. In that spirit, I bring you a classic post on European medicine in Siam (Thailand) from back in 2015, Tara Alberts’ “Making Drinkable Gold for the King of Siam.”

You may also notice several posts on a mini-theme of…shall we say uncomfortable recipes throughout the month of April, including historical treatments for lice and hemorrhoids already available to read (with more to come). Though I’d hardly put drinking gold at the same level of discomfort, and a fleck of gold leaf in a cocktail can still be a decadent indulgence today, I’d hate to see what a bellyful of Parisian golden medicine would do to a poor king’s stomach. Salud!


Making Drinkable Gold for the King of Siam

By Tara Alberts

In a previous post I discussed how early modern Catholic missionaries sought to showcase the most up-to-date European medicines to impress their target audiences. This was also a key strategy used to gain access to royal courts throughout Asia.

At the court of King Narai (r. 1656-88) of Siam, for example, Europeans joined experts from China, India, and elsewhere in Southeast Asia to provide medical advice to the royal family.  Narai’s court was a cosmopolitan place: the king was keen to hear about foreign technologies and theories, and to encourage foreign trade. The French missionaries of the Société des Missions Étrangères de Paris (MEP) were determined to take advantage of the opportunities that this offered.

Narai receiving the French Embassy, 1685. Wikimedia Commons
King Narai receiving the French Embassy, 1685. Wikimedia Commons

This could be easier said than done. It’s likely that the job of concocting remedies fell to René Charbonneau (1643-1727), a lay auxiliary to the MEP who had trained as a surgeon. In a 1677 he wrote a frustrated letter to a friend in Paris pleading for an easy-to-follow recipe written in French for aurum potabile. ‘The king has asked for drinkable gold’, he wrote ‘but we have not been able to manage it. […] Please write down in a letter the method of making it and purifying it for use, and the manner in which it is taken, written out in full in clear French and not in Latin and not in terms of chemistry as I am not versed in that art.’ (Archives des Missions Étrangères [AMEP] vol. 861, p. 41).

Gold-based medicines had ancient precedents in various European and Asian medical traditions. Like many putative panacea they enjoyed a renaissance in Europe in the late sixteenth and early seventeenth seventeenth centuries. [i] There were innumerable recipes available to create aurum potabile, often using gold flakes or powder alongside other expensive ingredients including precious stones, unicorn horn and spices.

Yet since the sixteenth century, many writers had been extremely skeptical about whether such cures could possibly be of use. The chemist Nicolas Lefebvre, in his Traité de la Chymie (1660), denied that they could have any effect on the human body. Mixing gold leaf into medical concoctions and powders, he asserted, was an ‘abuse in Pharmacy that the Arabs have introduced’ (p. 801). Such medicaments could not be effective as the human body contained nothing capable of breaking the gold down. Lefebvre doubted whether any efficacious cure could really be created from gold, but like other compilers of alchemical compendia, he provided a range of common recipes to purify and use gold in a more sophisticated manner.

An alchemist making gold. Oil painting by Hendrik Heerschop. The Wellcome Library, London
An alchemist making gold. Oil painting by Hendrik Heerschop, 1665

It seems that the MEP were attempting to use these sorts of alchemical methods to create a ‘true’ drinkable gold (rather than just creating a medicinal draught with added gold flakes) and that this was proving difficult. MEP missionary Charles Sevin (?-1707) blamed the equipment available in Siam. He explained in a letter to his Parisian superiors that they had brought the necessary ingredients to make the king some huile d’or potable, but the glass retorts they acquired there all shattered before they reached the necessary temperatures. (AMEP, vol. 851, p. 190).

Others confessed that their ignorance of alchemical processes was hindering progress. Charbonneau mentions that he had with him Christophe Glaser’s Traité de Chymie (1667). In this, Glaser explains several different ways of purifying gold, and offers several different methods for rendering this purified gold usable as a medical preparation through fulmination, calcination with mercury, or dissolution in the aptly named ‘royal water’ (eau régale or aqua regia – nitrohydrochloric acid). One recipe for a draught containing ‘diaphoretic gold powder’ for example, recommends that after purification the gold should be dissolved in three drams of royal water to which is added a dram of refined saltpeter. This liquid should then be used to soak small pieces of linen, which, once dried, should be burnt. The resultant ashes should be collected carefully using a hare’s foot or a feather and then used to make a pill or a draught using a small amount of wine or bouillon.

Glaser’s stated aim in writing his Traité was to set out the principles and practices of chemistry in plain language, but Charbonneau complained that he found Glaser’s text confusing. He and his confrères had had some success when they attempted to follow Glaser’s instructions with regards to purifying tin, but they were not confident enough to give a demonstration, nor, presumably, to waste their supplies of ingredients needed to make impressive remedies for the king.

There was a clear incentive to make a particularly impressive version of drinkable gold which would showcase the effectiveness of exotic European recipes, and by extension other branches of European knowledge. Yet even the most up-to-date texts explaining how to create these remedies were useless without the necessary skills and equipment to put the theory into practice. No wonder then that MEP superiors in Siam began soon to lobby for missionaries and lay helpers who were skilled in alchemy to be sent from Paris.

[i] Informative overviews of the history of pharmaceutical gold are provided here by R. Console, and here by M. Hendriksen.

Cold! A Recipe Project Thematic Series

Hiroshige, Two men by a gate in the mountains. Image from Wikimedia Commons.

– it’s cold! A dreary chill and rain have just descended across Europe and perhaps most of you are also cranking up the heat and bringing out winter scarves and hats. December has arrived and it seems apt for us to follow our fun and successful series on “Heat!” with a thematic series on “Cold!”. Within medical conceptions of the human body across a number of cultures, notions of hot and cold are hardly be separated. Within kitchens, craft and artisanal workshops, although heat played a crucial role in production processes, cold was also essential occasionally – especially if ingredients had to be preserved for a period of time, or if heat had to be tempered in some way.

To get ready for the long winter, our contributors have explored the notion of “Cold!” in a number of areas. Thijs Hagendijk returns to the RP with a post on the Dutch polymath and painter Simon Eikelenberg (1663-1738), detailing how cold features in the practices of his paint making with surprising insights.  Jean-Olivier Richard, a historian with interests in early modern natural philosophy, alchemy and environmental history, invites us reflect upon mankind’s impact on our planet by offering a reading of “divine recipes for a cooling earth”.

Having written about how to “treat the heat in 1793 Beijing”, Marta Hanson returns to the RP this month with a post titled “Treating the Deadly Cold in 1918 China”, co-authored with Michael Shiyung Liu. Returning to another theme explored in the Heat! Series – fertility recipes – Yi-Li Wu will tell us about Chinese formulas dealing with cold genitals, the standard historical explanation for male and female infertility.

Finally, as we move closer to the holidays, we offer a few posts to “warm” you up. Marieke Hendriksen and Ruben Verwaal return with more adventures with Boerhaave’s “little furnace” (go here for part 1 of their explorations). New contributor historian Reinhild Kreis will tell us about Christmas Cookies in 20th century Germany and our Tales from the Archives will feature the wonderful post on “snowballs” by Rachel Snell.

“Christmas Dessert of layers of fruit, arranged for color effect. ‘Snowball’ is one of the most attractive Christmas Desserts” from American Homes and Gardens, 1911.

We can’t do much about the chilly weather outside but we hope that this wide-ranging edition of the Recipes Project might distract you from the weather and inspire you to think about the cold and chills in different ways.

Enjoy and happy holidays!

Marieke Hendriksen and Elaine Leong

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Ps. This is my last edition for a little while as I’m taking a tiny break from editing the Recipes Project in 2019. Things have been all-go at the RP headquarters over the past few months, and we have some really exciting news to share with you after the holidays. So, watch this space and see you all soon, Elaine.

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.