Art of Fire

Antonio Neri, MS Fergusin 67, 1598-1600,
ink and water color; "Anibal and Martin"

In L'Arte Vetraria, Antonio Neri describes glass as "a fruit of the art of fire." He apparently liked this evocative phrase enough that he borrowed the words from an earlier volume written in the first half of the sixteenth century by Vannoccio Biringuccio. Biringuccio's De la Pirotechnia was a sort of bible for metal workers, refiners and miners. The author was in charge of an iron mine near Siena and in the late 1520's he became something of a local hero for casting cannons to help Florence defend itself in the great siege.

Neri’s opening line reads:

“Without a doubt, glass is a true fruit of the art of fire, as it can so closely resemble all kinds of rocks and minerals, yet it is a compound, and made by art.”

And here is Biringuccio, half a century earlier in 1540:

“… it [glass] is one of the effects and real fruits of the art of fire, because every product found in the interior of the earth is either stone, metal, or one of the semi-minerals.  Glass is seen to resemble all of them, although in all respects it depends on art.”

In one sense, Neri is paying homage to his distinguished predecessor, but he is also lending a new meaning to Biringuccio's words. The mining expert's short chapter on glass is a survey and a great deal of it is spent on the debate of whether glass should be classified as a 'semi-mineral' because of its similarity to rocks and gems, or as a metal because of its molten properties in the furnace. Neri puts a different spin on the fruits of glassmaking. He is not as worried about classification as he is excited about the material's many uses. He composes a formidable list for us, one that ranges from drinking glasses, to optical lenses, to church windows, to laboratory equipment.

Neri uses Biringuccio's chapter as a format for his own introduction; they both cover much of the same ground, but with a telling difference in tone. Biringuccio is very much 'old school.' His main concerns are taxonomy of the material and the construction of the equipment. For him, the finished products of glassmaking are more ornamental curiosities. He trumpets that glass objects hold more beauty than their metal counterparts, but he warns that we should not give them too much love because they are fragile and therefore, like life itself, ephemeral. Neri, on the other hand, agrees that glass can be beautiful, but he is all about the chemistry and the innovative things that can be done with this versatile material.

The differences in emphasis between the two men nicely illustrate a shift that was taking place throughout society in general. For hundreds of years, the focus of scholars and craftsmen had been on rehabilitating ancient knowledge. Europeans very much saw themselves as recovering from the long slow decline of medieval times. To learn the secrets of a craft, one looked backward, not forward, and the farther back the better. Ancient texts were prized and coveted because they were seen to contain purer wisdom, uncorrupted by centuries in the dark. Both men discuss the ancient origins of glass, recounting that it is mentioned in the Bible and by scholars of the Roman Empire like Pliny. The difference is that Neri's gaze is turning; instead of looking back so much, his eyes are shifting to the present. Biringuccio's Pirotechnia and books like it created a platform from which Neri and his generation could then build on. 

There are many definitions possible for the beginning of modern science. One that is compelling from a broad, non-technical point of view is that modern science began when we spent less time looking backward for answers and more time learning from the world as it is.
This post first appeared here in a slightly different form on 7 October 2013.

Turquoise Glass

Turquoise glass stamp
of calif Mustadi  c.1170.

It is estimated that turquoise is among the earliest gems ever mined. With colors that vary from pastel green to a bright sky blue, it has adorned Egyptian sarcophaguses of 5000 years ago, 3000-year-old Chinese art, Aztec death masks and the domes of Persian palaces. 

When traders brought it to Europe from the Mideast, it became known as "turks" or "turquoise" after the old French for "Turkish." While it has never been mined in Turkey, the most highly valued Persian stones were imported there and used extensively for trade. Polished pieces were famously mounted on Turkish equestrian saddles, in the belief that the material conferred sure-footedness and protection from injury during a fall.

As one of the first gems to be collected and traded, turquoise was also one of the first to be imitated. Egyptian faience blue is an early forerunner of glass. It is more porous than glass, but it contains all the same ingredients and could be cast into forms that look just like solid turquoise. In the seventeenth century, the genuine mineral and its imitation continued to hold importance. In Antonio Neri's book L'Arte Vetraria, the subject is mentioned several times; he offers one recipe to restore faded stones by soaking them in almond oil. For turquoise colored enamels he presents two different shades. On the subject of glass, he notes that "Sky Blue, or more properly turquoise, is a principal color in the art of glassmaking" and "I have made this color often, because it is very necessary in beadmaking and is the most esteemed and prized color in the art."

To make his imitation turquoise glass, Neri starts with a batch of high quality transparent aquamarine blue, to which he adds a specially prepared variety of common salt. "Add it little by little, until the aquamarine color loses its transparency and diaphany becoming opaque."

Take the sea salt known as black salt or rather coarse salt, since the ordinary white salt that they make in Volterra would not be good. Put this salt in a frit kiln or oven to calcine, in order to release all moisture and turn white. Next, grind it well into a fine white powder. This salt now calcined should be stored for the use of making sky blue or rather turquoise color as described below.

Sea salt is mostly composed of sodium chloride, which is like table salt that we use for food. However, it can include significant additional minerals, as implied by Neri’s description of it as "black salt." Additional elements can include sulfur, potassium, manganese and more. Regrettably, he leaves us with no further clues to its identity, nor does he explain why the recipe would not work as well with the salt available from Volterra. He goes on to advise that the mix should be used quickly, because if left to sit in the furnace, the glass would start to revert to an ugly transparent color. The remedy for this is to add more salt. He finishes with some practical advice for glassmakers about adding salt to molten glass:

The furnace conciatore should take careful note here, when you add this salt, if it is not well calcined it always bursts. Therefore, you should be cautious and shield your eyes and vision, because there is a danger you could be hurt. Add the doses of salt little by little putting in a bit at a time pausing from one time to the next until you see the desired color. With this, I do not rely on either dose or weight, but only on my eyes. When I see that the glass reaches the desired level of color, I stop adding salt. This all comes with experience. 

* This post first appeared her in a slightly shorter form on 9 April, 2014.

Olearius on Glass

Adam Olearius

In the autumn of 1633, a trade mission heavily laden with gifts headed east from northern Germany. The great duke of Holstein was sending an ambassador to Moscow to request the czar’s permission for travel rights along the Volga River. Holstein was the northernmost tip of the Holy Roman Empire, in many ways more  closely tied to Scandinavia than to their Habsburg overlords. This expedition was part of an attempt to establish an inland silk-trade route between Europe and the Orient. Such a route would eliminate the circumnavigation of Africa, shortening the trip and reducing risk. After several years and initial high hopes, it became clear that the effort was doomed to failure. Czar Michael I of Russia was enthusiastic about the project, but at the southern end of the route, the king of Persia was not so receptive. Nevertheless, the expedition did become famous for a different reason: a written account of the adventures of the diplomats.

Upon the delegation’s return to Holstein, their secretary Adam Olearius (1599-1671) published a book that chronicled their travels. [1] As a mathematician, astronomer and general polymath, Olearius provides an uncommon perspective of the various cultures, practices and technologies encountered. Ultimately, he was appointed royal librarian and keeper of the duke’s cabinet of curiosities. The book proved so popular that more comprehensive editions soon followed, adding the contemporary accounts of another traveler, Johann Albrecht von Mandelslo. [2]

The adventures described have no particular focus on glass, yet this and related subjects were discussed in a number of different passages, giving us a unique insight into the material’s place in those societies.

In August of 1634, the group arrived in Moscow. Having been granted audience with the czar, Olearius describes the procession of the entourage and enumerates a long list of the gifts they brought. Among them was “a great looking-glass, being an ell and a quarter high and half an ell broad, in an ebony frame, with boughs and fruits carv'd thereon in silver, carried by two Muscovites.” [3] An ‘ell’ was the northern european equivalent of a cubit or about 25 inches, so the mirror measured about 12 inches wide by 30 inches tall, not enormous by current standards, but quite an achievement in the seventeenth century. Glass workers would have to blow a large cylindrical bubble, cut it open and lay it flat on a polished marble surface. To be usable, the sheet of glass would have to be made without waves or defects and it would have to be cooled slowly, over a period of many hours in order not to form cracks. Silvering the back was a whole other ordeal performed by an artisan schooled in alchemy.

Speaking of the chemical arts, gifts from the duke of Holstein to the czar of Russia also included “an ebony cabinet, garnish'd with gold, like a little apothecaries shop, with its boxes and vials of gold, enrich'd with precious stones, full of several excellent chymical extractions, carried by two Muscovites” [4]

While in Moscow, Olearius put on a demonstration of optics for some locals. “I shew’d them upon a wall of an obscure chamber, through a little hole I had made in the shutter of the window, by means of a piece of glass polish’d and cut for optics, all was done in the street, and men walking upon their heads: This wrought such an effect in them, that they could never after be otherwise persuaded than that I held a correspondence with the devil.” [5] Here he is describing a ‘camera obscura’ in which scenes from outside are projected upside-down onto the wall of a darkened room.

A couple of years later, after a return to Holstein to ratify a treaty with the czar, the delegation arrived in Persia. They were treated to a sumptuous meal by the king’s chancellor. “The walls were all set about with looking-glasses, to the number of above two hundred, of all sizes. So that when a man stood in the midst of the hall, he might see himself of all sides. We were told that in the king’s palace, in the apartment of his wives, there is also a hall done all about with looking-glasses, but far greater and much fairer than this.” [6]

“For the teaching of astronomy they have neither sphere nor globe, insomuch that they were not little astonished to see in my hands a thing which is so common in Europe. I asked them whether they had ever seen any such before. They told me they had not, but said that there was heretofore in Persia a very fair globe which they call ‘felek’, but that it was lost during the wars between them and the Turks. They haply meant that which Sapor, king of Persia, had caused to be made of glass, so large, that he could sit in the center of it, and observe the motions of the stars and must no doubt be like that of Archimedes, where of Claudian speaks in the Epigram which begins thus: Jupiter in parvo cum cerneret aehera vitro.” [7]

Olearius goes on to describe the Persian army in some detail, including this account of an early form of chemical warfare. “At the siege of Iran, in the year 1633, they had the invention of casting into the place with their arrows, small glasses full of poison, which so infected the air that the garrison was extremely incommodated thereby and made incapable of handling their arms for the defense of the place.” [8]

In 1637, near Tehran, Iran, he describes a royal tomb “adorn’d all about with glass of all sorts of colors, which are preserved by iron grates.” [9] And in the same area,

“At Kimas, in the province of Kilan, there was one of these mountebanks, who having found out the trick of setting cotton on fire by means of a crystal cut in half-round and held in the sun like a burning-glass, would have people persuaded that by operation, which he affirmed to be supernatural, that he was of the kindred of Mohammed. After our return to Holstein, I shew’d the Persians, whom Schach-Sefi [king of Persia] sent thither, that it was the easiest thing in the world to get fire from the sun, and I lighted paper in the very depth of winter by means of a crystal full of cold water, or a piece of ice, which I had made half round in a pewter dish. They were astonish’d at it, and said, that if I had done as much in Persia, I should have pass’d there for either a great saint, or a sorcerer.” [10]

As an addendum, in later editions of Olearius’ book, the recollections of Johan Albrecht de Mandelslo (1616–1644) were added. He accompanied an unrelated trade mission to Isfahan, Persia, and then split from his group to continue touring the region. He traveled through India, and then down the African coast. In 1639, the German traveler passed through Madagascar. He commented on the inferior quality of European glass trade-beads, compared to those of India, which he acquired earlier in the trip.

“The glass-bracelets, beads and agates, we had brought from the Indies [India] were incomparably beyond what they were laden with out of Europe; so that it was resolved ours should not be produced, till the others were sold. By this means, we bought every day four oxen for forty pair of glass bracelets, which the inhabitants call ‘rangus’; a sheep for two, and a calf for three ‘rangus’; and for a brass ring, ten or twelve inches about, a man might have an ox worth here six or seven pound.” [11]

Much has been made of the use of glass trade-beads by Europeans around the world.

In Madagascar and along the trade routes of the Indian Ocean, European traders were fairly late to the party. For a thousand years earlier, [12] beads had been used as the currency of choice among disparate cultures from Indonesia and China to India to Africa who did business with each other.[13] The above quote from Mandelslo’s diary provides a fascinating firsthand account of transactions with beads. The passage also hints at the superior quality of Indian glass beads. Today, glass beadmaking continues on an industrial scale there, and the glass bracelet industry still survives, notably in Firozabad, northern India.

[1] Adam Olearius: Beschreibung der muscowitischen und persischen Reise, (Schleswig: 1647).

[2] Adam Olearius, John Davies, Johann Albrecht von Mandelslo, Philipp Crusius, Otto Brüggemann: The Voyages and Travells of the Ambassadors Sent by Frederick Duke of Holstein, to the Great Duke of Muscovy, and the King of Persia... (London: John Starkey, and Thomas Basset, 1669).

[3] Ibid, p. 11.

[4] Ibid.

[5] Ibid, p. 58.

[6] Ibid, p. 212-213.

[7] Ibid, p.252. Jupiter in parvo quum cerneret æthera vitro [When Jove a heav’n of small glass did behold,] see Henry Vaughan: Silex scintillan, Hermetical physick, Thalia redivava, Translations, Pious thoughts and ejaculations. (Oxford: Clarendon Press, 1914) v. 2, p.635.

[8] Ibid, p. 271.

[9] Ibid, p 182.

[10] Ibid, p. 280-281.

[11] Ibid, p.204.

[12] For example warring states beads in China, see https://en.wikipedia.org/wiki/Ancient_Chinese_glass

[13] Carla Klehm has a nice post on the subject of trade beads used around the Indian Ocean; see “Trade Tales and Tiny Trails: Glass Beads in the Kalahari Desert” in The Appendix, Jan. 2014, v. 2, n. 1. http://theappendix.net/issues/2014/1/trade-tales-and-tiny-trails-glass-beads-in-the-kalahari-desert

Donato Altomare

Donato Altomare, engr. C. Biendi,  from

 "Biografia degli uomini illustri del regno di Napoli,"

In sixteenth century Europe, it was not easy being a physician if your philosophy of medicine deviated from the norm. In those days, the 'norm' was to treat all diseases solely based on elementary properties or "humors" as they were called. Successful treatment, according to theory, depended on the restoration of balance between the four humors which were in turn associated with air, water, earth and fire. For example, symptoms that included a burning fever called for a diametrically opposite treatment than for a patient with chills. Sometimes these procedures worked, other times not so much. These principles were very old; they had been established centuries earlier in the writings of Hippocrates and Galen and the wisdom of the ancients was not generally questioned. The medical establishment was locked into these concepts and to deviate was to risk severe criticism from one’s professional peers. 

An early maverick was one-time mining physician Paracelsus. Today he is known as a pioneer of sorts; he focused his attention on practical solutions that worked in the field rather than on dogmatic theories. He insisted on basing his treatment, not blindly on a set of rules, but on close observation of his patients and of nature. Increasingly, his peers considered him a dangerous crackpot and a liability for his unorthodox treatments. He spent the last part of his life running from one town to another, trying desperately to stay ahead of his detractors. The fact that he was also outspoken about his belief of an impending apocalypse did not help his case. He died in 1541 and his ideas about chemistry and medicine did not start to gain traction until about fifty years later, when among many others, alchemists Antonio Neri and his sponsor Prince Don Antonio de' Medici became devotees.

Paracelsus is an extreme example, and perhaps the best known, but he was far from alone in a rising tide of debate about the nature of disease. A much lesser known example, one that peripherally involved Neri's own father was that of Neapolitan physician Donato Altomare who was a university professor in the middle of the sixteenth century. He was hounded out of Naples and forced to relocate in Rome after favoring the opinions of leading Arab physicians over established theory, but philosophically, he was still very much in the mainstream of promoting the ideas of Galen and Hippocrates. The old ideology was held so tightly, that even a slight deviation could leave a career in ruins. Ultimately, Altomare found favor with fellow Neapolitan Pope Paul IV, rehabilitated his reputation and was allowed to return to his hometown, but criticism persisted. One of his most vocal detractors was a classmate of his own son, named Salvo Sclano. 

In 1585, a book on a variety of topics in medical theory was published by one of the leading doctors, Antonio Alvarez, personal physician to the Viceroy of Naples. In Epistolarum et Consiliorum Medicinalium pars prima, Alvarez invited a number of well-respected peers to contribute chapters in the form of letters. The book is most noted for the final chapter in which Alvarez mounts a spirited defense of the above-mentioned Donato Altomare and against his nemesis Sclano.

Antonio Neri's father, Neri Neri, has a detailed chapter in Alvarez's book. The elder Neri was the personal physician to the grand duke of Tuscany, Ferdinando de' Medici. In his piece, he wrote on the treatment of what was known as "left side paralysis," usually the result of a stroke, which often left patients physically debilitated and unable to speak. This same malady befell a close Neri family friend in the 1560's. Poet and historian Lodovico Domenichi spent the end of his life unable to speak, but still attended by his best friend, Antonio's grandfather, Jacopo Neri. The medical problem was correctly identified as originating in the brain, but the prescribed treatment was, shall we say, less than optimal. An incision was made in the rear of the patient's head at the base of the skull. Wires or small beads were inserted to keep the wound open. The theory was that deep pathogens were drawn out of the body, as evidenced by the large discharge of puss that resulted. 

The fact that Neri Neri contributed to the book is an indication that he was in sympathy with Alvarez's defense of Altomare. It is interesting that while he was quietly championing the minor revision of  main-stream Galenic medicine, his son Antonio would go on to champion the far more radical teachings of Paracelsus. While the majority of Antonio's writings deal with medical cures, nowhere does he discuss the theory of "humors" or Galenic medicine, although he also does not speak out against it. In his own quiet way, Antonio Neri was helping to sever ties to the old ways of medical practice. In the future, the emphasis of medical science would be squarely focused on careful observation of nature.

*  This post first appeared here as "Physician Steel Thyself" on 30 July 2014. 

The Neighbors

"Portrait of Giamologna"by Hendrick Goltzius

In Florence, directly across the street from the Palazzo Neri, where glassmaker Antonio Neri spent his youth (now the Marzichi-Lenzi), was the residence and workshop of famed sculptor Giambologna. This two-building compound was a 'gift' to the artist from the newly crowned Grand Duke Ferdinando de' Medici, in 1587. It was intended to settle debts incurred for the artist's work by the previous grand duke, Francesco. The dwelling, at 26 Borgo Pinti, was located on the same street that was formerly inhabited by the likes of Michelangelo, Perugino, Pontormo and Cellini.

Neri's father, the royal physician, had collected art. According to historian Giovanni Cinelli, in 1677, when Antonio Neri's nephew owned the property, among the pieces in the house were:

Two small bronze horses by Giambologna, many works of [Simone] Pignoni and others, among which are two marvelous holdings; a waist-up Ecce Homo by Titian and a Satyr of beautiful ancient bronze which is wonderfully captivating; it is of the Greek manner and expresses an attitude of prompt movement that recalls liveliness, the muscles are very well prepared. Finally, a statue of Cupid flanked in marble in the best Greek style.

Giambologna had a strong influence on Florentine art and his work was to be found throughout the city, from the courtyard of the Palazzo Vecchio, to the gardens of the Casino di San Marco, where Neri made glass. The sculptor was well known for the fine surface finishes he achieved on marble and for his ability to resolve the technical challenges of portraying multiple figures, especially those involving a complex intertwining of limbs and bodies. The Rape of the Sabine Women, completed when Neri was a boy, is considered his crowning achievement.

Giambologna was born in Douai, Flanders, now in France, as Jean Boulogne. He landed in Florence in 1553, after a period working in Rome for Pope Pius IV among others. The Medici never allowed him to leave Tuscany for fear that once out of their reach, he would be enticed to go to work for another of the European sovereigns, never to return. It is reasonable to speculate that before his own trip to Flanders in 1604, Antonio Neri offered to relay messages or other effects to the family of his seventy-five year old former neighbor. Neri spent seven years with his friend Emmanuel Ximenes in Antwerp. Before his return to Tuscany, in 1611, both Grand Duke Ferdinando and Giambologna had already gone to meet their maker.

Neri had left Florence in his twenties, and returned in his thirties to a very different city. He settled down to write the book for which he will forever be remembered, L'Arte Vetraria, the first printed book devoted to the formulation of glass.

This post first appeared here on 20 Sept. 2013.

San Giusto Alle Mura

Window of  Santa Maria del Fiore cathedral,
Florence, Italy.

In Florence, at the very end of the street on which Antonio Neri spent his youth, Borgo Pinti, was the residence and estate of the Archbishop. Beyond were the city walls and the enormous wooden doors of the Porta Pinti gate (115 foot, or 35 meters tall). Just on the other side of the gate, which in Neri’s time was normally closed and guarded, once stood the San Giusto alle Mura monastery, built in the thirteenth century. Despite the similar name, there is no connection between the Ingesuati monks of San Giusto and the modern order known as the Jesuits, which was not formed until 1534 and recognized by the Church in 1540.

The monks at San Giusto were famous for the stained glass windows they made; hence one of numerous theories that the name 'Pinti' may be a contraction of 'dipinti 'or 'dipintori' (paintings or painters). Using their own glass furnaces, the Ingesuati monks provided windows for the Neri family's church Cestello and for Santa Maria del Fiore among other churches. They also ran an art school and were famous for making the color pigments used by painters, producing a coveted ultramarine blue. Their customers included the likes of Leonardo, Michelangelo, Botticelli, Del Sarto, Ghirlandaio and Filippo Lippi. 

Apparently, the Ingesuati's artistic devotion was not matched by their religious observance. In his Lives of the Artists, Giorgio Vasari recalls the less than complimentary sentiments of the monk's own in-house chaplain, a certain Servite monk named Fra Martino. He notes that the monks do not read Mass, and that they, "do nothing but say paternosters ['our Father...'], make glass windows, distill herbs for sweet waters, dig their gardens, and perform other works of similar kind, but do not study or cultivate letters."

Antonio Neri has a slightly more positive opinion about the value of stained glass windows. In the introduction to L'Arte Vetraria, he waxes poetic: 

Glass is also a great ornament to God's churches since, among other things, many beautiful windows are made, adorned with graceful paintings, in which the metallic colors are so intense and vivid that they seem like so many oriental gems. 

The windows that inspired these lines may well have been made by monks of San Giusto. As a child, Antonio Neri had seen the striking windows in Cestello and in the city cathedral. It would be nice to be able to connect him to the Ingesuati, but in 1529, long before his birth, their entire complex just outside the Pinti Gate was dismantled in defensive preparation for the siege of Florence. The Florentine military cleared away the structures near the outside of the city walls. The monks of San Giusto alle Mura moved to the much smaller Calza Convent on the oltrarno, on the opposite side of town near the Porta Romana gate. They did not rebuild the glassworks at the new location and it is doubtful that any of the glass workers would have still been alive by the time Antonio Neri came of age.

This post first appeared here in a slightly shorter form as "Glass Monks" on 30 September 2013.

Vitrum Flexile

Abraham Drentwett (the elder),  c.1647-1727
Vulcan Making Arms for Achilles, while Venus and Cupid Look On.

In the first century CE, references appear in the literature for a malleable form of glass, the method for which is reported as lost. This 'vitrum flexile' was a material that supposedly could be worked with a hammer like metal; not brittle but plastic, yet retaining the other favorable properties of glass. In the ancient world, historians Strabo (c. 63 BCE–24 CE), Pliny (c. 23–79 CE), Petronius (c. 27–66 CE) and others recount the story of a hapless artisan who brought his great discovery to Roman emperor Tiberius. Fearing the devaluation of his wealth, the emperor had the glassmaker executed on the spot and his workshop destroyed. The implication being that the inestimable value of a malleable glass would crash the markets for gold and silver. [1]

Since then, the legend has resurfaced in various forms, notably at periods in history of technological upheaval; times when innovative knowledge threatened to 'disrupt' the established order. One incarnation has the sophy of Persia gifting a set of malleable drinking glasses to the king of Spain, Philip III, around 1610. Just then, new trade deals with the Middle East rattled the European economy and Venetian glass craftsmen fanned out through Europe, disrupting local glass furnaces and guilds with their superior techniques. [2] Another version tells of a French sculptor bringing his malleable glass-work to Cardinal Richelieu (1585-1642), of Dumas' Three Musketeers fame. According to the story, that particular artisan’s reward was life in prison. The tale takes place in a tumultuous political period in French history and appears in print at the dawn of the so-called industrial revolution. [3]

Chronologically, this last story aligns nicely with the publication, in southern France, of a Latin book of alchemical recipes by royal physician Pierre-Jean Fabre (1588-1658). Contained in his volume is a prescription for a malleable form of glass, presumably the fabled vitrum flexile. Fabre's book was titled Palladium Spagyricum, 1624. [4] Spagyricum is a reference to spagyrics, the specific brand of chemistry practiced by sixteenth century alchemist-physician Paracelsus. Palladium translates to 'protector' or 'savior'. As an aside, it is interesting to note that Fabre developed an elaborate philosophy which integrated chemistry as a 'sacrament' to Catholic theology, but that is a story for another day.

In 1685, Fabre's recipes were nicely translated into English and tucked into the end of a book otherwise devoted to the art of drawing, by William Salmon [5]. Here is the full recipe "To Make Malleable Glass" as rendered in Salmon's book:

I.        Take oyl of Luna, twenty drachms: oyl of Mercury, or its water seven times rectified, one pound: mix them together and distill them.

II.      Repeat this distillation till the oleum Lunae rises with the water of Mercury in distillation. 

III.     Distill this water again until it is fixed, and converted into a fixed oyl, and this repeat four times. 

IV.     In the fourth time the oyl of Luna is fixed with the oyl of Mercury, so that they render glass malleable; for so great is the viscosity in your oyls, that it removes the brittleness of the glass, and so leaves it of a malleable temper. 

V.      The reason is, because that the radical moisture of the glass is multiplied by the radical moisture of the metals. Which is plentiful and turgent or swelling in the oyls of Luna and Mercury. 

VI.     And if [in] this oyl made volatile, diamonds should be dissolved, and then digested into a fixt oyl, it would transmute all glass into diamonds, only by projecting this oyl onto melted glass. 

VII.   There are also other precious stones comprehended within this oyl, when it is made volatile, and digested, and fixed again by digestion continually for the space of a year. 

VIII.  Also this oyl can turn glass into precious stones of any kind whatsoever, if therein (being made volatile) precious stones of the same kind have been dissolved, and digested with it into a fixed oyl. 

IX.     For as metals are included in their fixed oyls: so are precious stones in theirs, as Raymundus Lullius doth witness in many places; the which thing we shall teach you in the following chapter. 

 Elsewhere in the book, it is explained that 'oyl of Luna' is silver dissolved in acid, and 'oyl of Mercury' is a sublimation of mercury and saltpeter. [6] From a purely technical standpoint, the formula is credible in that both mercury and silver were successfully used as additives to glass and they do integrate into the matrix. Notably, Antonio Neri used both of them in his chalcedony glass. In Neri's case he was using these metals to produce color, although he does not attribute a specific tint to these ingredients. Under some circumstances, silver is known to produce an attractive blue. It should also be noted that Renaissance glassmakers used similar silver-mercury formulas to produce a reflective layer on finished glass mirrors, in a process that resembled gilding. They formed what was known as "mercury glass." It is not beyond the pale to speculate that experiments would be conducted to add such concoctions directly to the glass melt. In the end, though, there is no indication that these additives would produce a malleable glass.

As far as I am aware, this is the first example of a specific recipe for malleable glass uncovered in the literature. If nothing else, it is an important marker for further research into the history of glassmaking.

[1] Strabo: Geography, v. 8; Pliny: Naturalis Historia XXXVI.lxvi.195; Petronius: Satyricon 50.7; Also recounted by Casius Dio (c.150–235 CE): Historia Romana 57.21.7; Isidore of Seville (c. 560–636 CE): Etymologiae XVI.16.6, ‘De vitro’; Suetonius; Ibn Abd Alhokin; John of Sailsbury.

[2] Knolles, Grimstone, Johnson: Richard Knolles' The General Historie of the Turkes (London: Adam Islip, 1621).

[3] Neri 1697 (Introduction). A French translation of Florentine glassmaker Antonio Neri’s 1612 book L’Arte Vetraria [The art of making glass] by Jean Haudicquer de Blancourt. Also see my earlier post here http://www.conciatore.org/2014/07/flexible-glass-reprise.html .

[4] Pierre-Jean Fabre: Palladium spagyricum Petri Ioannis Fabri doctoris medici Monspeliensis ... (Toulouse: Bosc, 1624), p. 276. Later translated into several English editions, see note [5].

[5] William Salmon: Polygraphice: Or the Arts of Drawing, Engraving, Etching, Limming, Painting … (London: T. Passenger & T. Sawbridge, 1685), pp. 598, 599.

[6] To more adventurous readers: DO NOT TRY THIS AT HOME, or anywhere else, ever. Vaporized mercury is a powerful neurotoxin. Small amounts can cause permanent brain damage and multiple organ failure. Furthermore, this recipe uses powerful acids and nitrates, which are extremely dangerous even in a controlled laboratory setting. Even if you have little regard for your own health and safety, consider those around you; this includes loved ones, family, children, pets, neighbors and the emergency workers who will inevitably be left to clean up your mess.