Dear Readers,

As you may have seen elsewhere, in mid February my wife and I suffered the loss of our home in a fire, in the hills of central Massachusetts. The good news is that we got out safely and had no animals in our care at the time. The fire crews were able to contain the fire from spreading, in what turned into a 3-alarm, 5-hour-long ordeal in subzero temperatures; they did amazing work, and no one was injured. The bad news is that all of my physical historical materials and research of 30 years have gone up in smoke. As a result I have decided to suspend this blog for the time being. It will remain online as a resource for those interested in the history of glass and glassmaking in the seventeenth century and beyond. I do intend to resume writing when I can, but for now my time and energy are required in getting us back on our feet.

Friends are providing temporary shelter for us nearby and our intention is to rebuild as soon as possible. To those who have reached out with a steady hand, to those who have opened their wallets, and offered advice in our time of need, we thank you from the bottom of our hearts. In what are already difficult times for all of us, you have made a huge difference in our lives.

Paul Engle
6 March, 2021

Friday, February 27, 2015

Antonio Neri's Birthday

Relief portrait of Antonio Neri,
artist unknown, La Specola Museum,
Florence.
Glassmaker Antonio Neri was born in Florence, Italy on 29 February 1576. Because he was a "leap year baby" we celebrate on 1 March in off years. From his baptismal record, we actually know the exact time of birth: "three hours and 25 minutes past sunset." In terms of current timekeeping conventions, sunset occurred on that particular Thursday at about 6:15 pm CET (local time), so the big event happened at 9:40 pm.

It might seem a bit odd to have such accurate records -- almost as if an astronomical event were being recorded. Actually, that is exactly what was being done; astrology of the sixteenth century drew a strong correspondence between 'macroscopic' events in the heavens and more earthly matters. To have an exact time of birth was seen as a way to gain greater insights into the events of ones personal life and to plan in a way that was more in harmony with the natural order of things.

Of all the days to be born, 29 February was considered among the least auspicious. A dire Northern Italian folk proverb states "An bisesti, o la mama o 'l bambi" predicting that, born on this day, a child or its mother was fated to die by year's end. Indeed, the Italian word naming the day, bisestile, had become a synonym for misfortune or calamity and is still the case for the French cognate bissêtre. Whatever stock the family put into ancient superstitions, happily this prophecy did not come true for Dianora or her fourth child Antonio.

Although his was a February birth, it was perhaps not as deep into winter as one might assume. Due to a discrepancy in the Julian calendar, which was in force then, the Spring equinox of Neri's birth year happened much earlier in the calendar than today, around 10 March, in fact. 

Infant mortality was not uncommon and for a child to die unbaptized only magnified a family's trauma. Church theologians had debated since the fourth century on the fate of the souls of such children. Most Catholic families baptized infants as soon as humanly possible, in Antonio's case the very next morning. Births occurring within Florence were officially registered at a central baptistery, San Giovanni, the ancient octagonal basilica standing directly in front of Florence's main Cathedral. 

The full baptistery record, in translation, for Antonio Neri reads:
Thursday, 1 March 1575:  Antonio Lodovico was born to Mr. Neri di Jacopo and Dianora di Francesco Parenti, residents of San Pier Maggiore parish. The time of birth was 29 February, at 3 hours 25 minutes past sunset. The godparents are Francesco di Girolamo Lenzoni and Ginevra di Federigo Sassetti.
The year is recorded as 1575 because in those days, Florentines celebrated the New Year on 25 March. Today we consider January, February and March to be part of the new year. 

Antonio joined a growing family that already contained siblings Lessandra, Jacopo and Francesco, and later would number ten children.  His father was thirty-six year-old Neri di Jacopo Neri, (Neri Neri to his friends) and his mother was twenty-one year-old Dianora Parenti. Neri Neri was a prominent doctor and later was appointed to be the personal physician to Grand Duke Ferdinando. Dianora was the daughter of Francesco Parenti, Michelangelo's lawyer. 

Tradition dictated that births were celebrated with a house party open to friends and neighbors. Thirty-four year-old Francesco Lenzoni, Antonio's godfather, would certainly have done his best to attend. His family included Florentine senators and Francesco himself would later become Tuscan ambassador to Spain. Godmother Ginevra Sassetti, in her late fifties, was also from a prominent family. Her nephew Filippo would send plant specimens back from India to be inspected by Neri Neri and their mutual friend Baccio Valori who would become director of the Laurentian Library in Florence.

Antonio Neri, would go on to learn the finer points of alchemy and glassmaking, developing new formulas and techniques that would be applied throughout Europe. In 1612, he published the world's first book entirely devoted to formulating glass, L'Arte Vetraria. It seems especially appropriate that we pause and raise a toast (in glass, of course) to his accomplishment and to the end of February, looking forward to warmer days ahead.

Wednesday, February 25, 2015

Alberico Barbini

The island of Murano , circa 1600
attributed to Danckerts
In the early seventeenth century, Antonio Neri began preparing batches of glass for the royal family in Florence, Italy. This was a specialist vocation undertaken by alchemists, which by schooling Neri was. His job as “conciatore” involved procuring the ingredients, preparing, mixing and melting them and working with the glass artisans, adjusting the consistency and colors for the work being done. It was a position that carried great prestige, and Neri’s book on glassmaking [1] would cement his name in history. 

Shortly before Neri was born, in 1576, the grand duke of Tuscany, Cosimo I de’ Medici, brokered a special deal to have master glass artisans come to Florence and teach their secrets. These men were from the island of Murano, in Venice; the most famous center of glassmaking anywhere. There is only scant evidence that Neri himself traveled to Venice and perhaps only once, but there is no doubt that he benefited greatly from the knowledge of Muranese workers in Florence, Pisa and Antwerp during his lifetime. 

Over the intervening centuries, the title of the glass batcher changed, but the tradition and prestige of glass formulation continued well into the middle of the twentieth century. In fact, even today, among the small glass manufacturers that cater to the studio glass movement, the glass batcher is considered to be something of a modern alchemist; keeper of the arcane knowledge of  the chemicals and amounts necessary to produce special colors and adjust properties of the glass.

In the early 1920s, a Milanese lawyer named Paolo Venini partnered with a Venetian-born antique dealer friend, Giacomo Cappellin, to start a new glass factory on Murano. [2] Even as recently as this, the glass batcher held a respected position both within the factory and the community. Through several incarnations over the next half century Venini grew a world-wide reputation for innovative designs, of which color played an important part. They are specifically associated with the fazzoletto (handkerchief) style vase and the incalmo technique of fusing two or more colors of glass seamlessly in a single furnace-blown piece. 

In 1925, Cappellin split from Venini and took many of the craftsmen with him, in 1933 the new business was acquired by Pauly & C. Again, chemical knowledge and the artistry of reproducing ancient colors made a worldwide reputation. [3] As ownerships changed hands like cards in a game and artisans shuffled between factories, it is easy to lose track of the individual glassworker. Even for a period so recent, many records exist only in the heads of the family members still living on the island. 

In 1956 the Stazione Sperimentale del Vetro (Experimental Station for Glass) was started on Murano with the mandate to preserve and promote the technical aspects of Italy’s glassmaking heritage. [4] The new institution was regarded by some traditionalists with great suspicion, but as we will see, others embraced the resource.

I recently sat down with my friend Emilio Santini, who today carries on a six-centuries-old family tradition in glasswork. [5] Emilio had recently called home to Murano, which led to his father’s recollection of an uncle, who worked making color for Venini and Pauly. Here Emilio recounts the conversation:
Alberico Barbini was the uncle of my father, Mario Santini and the man in charge of making the glass batch “partie” (Venetian) “partite” (Italian). He was the brother of my grandmother, Delfina Barbini. He was not the only one [in my family] who worked for Venini in the early days but the most respected. At Venini he worked formulating glass after another great batch maker, [Albino] Carrara. 
In the early to mid [twentieth] century the batch maker still held an important position in the factory, not like now, you know, and he kept his formulations quite secret, although this relative of mine, Alberico, was smart enough to use the most modern technology available at that time. 
He was different from other batch makers in that when the Stazione Sperimentale del Vetro opened, he made extensive use of it in reproducing colors. At that time, and even now to an extent, the institution was not seen as good for traditional Murano glassmaking. 
He later moved on to Pauly where he was in charge of reproducing the glass colors that were in use in the seventeenth, eighteenth and nineteenth centuries. First, he assisted in remaking broken or missing pieces in private collections, then later in making reproduction antique stemware at Pauly that was impossible to distinguish from the originals. 
You must realize that all this does not come from documents but from the memory, still very sharp and lucid, of my father.


[1] L’Arte Vetraria, (Neri 1612).
[2] Paolo Venini http://en.wikipedia.org/wiki/Paolo_Venini also see https://www.facebook.com/pages/Venini/198475426829887
[3] Pauly & C. Compagnia Venezia Murano http://en.wikipedia.org/wiki/Pauly_%26_C._%E2%80%93_Compagnia_Venezia_Murano
[4] Stazione Sperimentale del Vetro  http://www.spevetro.it/indexENG.htm
[5] Emilio Santini http://www.cmog.org/bio/emilio-santini

Monday, February 23, 2015

Gold Ruby Redux

A gold florin.
Legend claims gold ruby glass
 was discovered when a nobel threw
a gold coin into a glass maker's crucible.
Antonio Neri is best remembered for writing L'Arte Vetraria. It was the first printed book entirely devoted to the formulation of glass, which he published in Florence, Italy, in 1612. If we were to single out just one of his more than a hundred recipes, covering glass, lead crystal, paste gems and enamels, it would have to be his prescription for "Transparent Red" ruby glass made with gold. This recipe still captivates glass artists today, as it has since Neri wrote the book. In fact, gold ruby glass is closely tied to the lore of alchemy and has intrigued experimenters as well as artists and collectors since the Roman Empire, possibly before.

Alchemists had long thought gold to be the perfect metal and that all other "lesser" metals (read: lead, tin, copper, iron, mercury and silver) could be coaxed to fully "mature" into gold. Experimenters thought that if they could capture the "essence" of the king of metals, it could be used to "seed" the other metals, and transmute them into pure gold. This is where ruby glass comes into the discussion. In general, glass is colored by the addition of finely powdered metals. Depending on the metal and how it is treated, a whole rainbow of colors can be produced in glass. Alchemists were convinced that the color was an indication that this "essence" of the metal had been released into the glass. 
Cranberry glass or Gold Ruby
 treasury chamber of the Wittelsbacher , Munich Residenz.

For artists and collectors, gold ruby is simply a very attractive color; the difficulty of producing it and working with it only adds to its cachet. Transparent red in glass can be produced other ways, notably with copper, but copper red has a slightly more orange color. Gold ruby, on the other hand, has a characteristic red color that can have slight hints of purple. It can be made light and ethereal or dark and heavily saturated, but viewed next to its competitors, it has a very distinctive hue that experts pride themselves on recognizing.

Neri’s recipe involves moistening gold powder with "aqua regia," which we know as a mixture of nitric and hydrochloric acids. He then spreads this wet mixture on an earthenware pan and heats it in the furnace "until it becomes a red powder, which will take place after many days." Here is that color change that alchemists looked for as an indication of transformation; we know today that Neri was producing gold chloride. This is one of the very few chemical compounds that gold forms and in fact, this is one of the main things that makes gold so special: it does not rust, nor corrode or tarnish, which are, in the end, all chemical reactions between the metal and its environment.

Neri directs his readers to sprinkle, little by little, the gold chloride into the glass melt. He says to "Use fine cristallo, thrown in water many times." Cristallo is the exceptionally clear glass invented by Venetian craftsmen, and "washing" was a technique to remove excess water soluble flux and other contaminants. He finishes his instructions abruptly by saying this method "will make the transparent ruby red glass; but you must experiment in order to find it." In other recipes, Neri goes to great lengths to explain his methods in detail, here he seems content to barely scratch the surface. Much speculation has taken place over the reason for this surprisingly short recipe. Was he ordered, perhaps by his Medici overlords, to keep details to a minimum? Some have wondered if Neri even knew how to produce gold ruby; the short recipe may have been a cover for his lack of knowledge.

Doubts about Neri's gold ruby glass recipe grew after his death, when it was discovered by other experimenters that the addition of small amounts of tin into the mix produced the ruby color quickly and reliably. This compound of tin and gold chloride was called "Cassius purple" after one of its inventors and its color. In some circles it was thought that the tin was an essential ingredient, a lost secret that had been rediscovered. The argument was that gold chloride alone could not produce the color, it must be combined with tin in the form of Cassius purple. However, this is not the case. 

In an 1846 edition of the Journal of the Franklin Institute (ser. 3, v. 11), professor of chemistry and natural philosophy, E. L. Schubarth, cites numerous investigators who demolish this theory. He wrote:
It must not be imagined from this, as some persons have lately stated, that it is necessary to use gold [combined with tin] in the state of Cassius purple.
Neri, at the end of the sixteenth and commencement of the seventeenth century, stated, that in order to stain glass a ruby color, it was only necessary to employ calcined chloride of gold. At a later period, Libar wrote to the same effect, and Merret certified that he had proved the efficacy of the process. In 1834 Golfier Besseyre stated, in the Journal of Pharmacy, that Douault Wieland colored his paste with perchloride of gold only. Lastly, in 1836, Fuss writes, that in Bohemia all the ruby-colored glass was prepared with chloride of gold only, and that glass might be stained red as well with metallic gold, as with oxide of gold or Cassius purple.
It is therefore a fact known for some time, that glass may be stained red, without either Cassius purple or oxide of tin, with [only] metallic gold or preparations of gold. In the glass-works of Bohemia and Silesia perchloride of gold only is used, without the addition of oxide of tin, in order to produce their fine rose or carmine-colored glass.
Of the men cited, Douault-Wieland was a Parisian jeweler who was famous for his artificial gems and crystal glassware. He was praised for his skills by Napoleon. Paul Golfier-Besseyre was a well respected French chemist. Besides many other endeavors, he worked for the glass industry and performed numerous experiments on the formulation of glass. He produced a gold ruby using the same ingredients as Neri. He determined good color could be achieved by letting a new batch of the glass age for a protracted period of time at temperatures below the melting point of gold. Periodically, he removed the glass from the furnace and poured it into water to wash it. The result was a yellowish glass when molten, but when a gaffer finished a piece it was gently reheated and the ruby color developed. 

Friday, February 20, 2015

Incalmo

Incalmo vessels by Tapio Wirkkala for Venini.
In a new series of occasional posts to this blog, we will explore some of the classical techniques of glass art. Filigrana, latticino, reticello, incalmo, pezzato; many of these terms are well established in the lexicon, even if poorly understood. Many glass artists practice these techniques, but have only a dim idea about when and where they were invented and used. Here we will attempt to clarify both the origin of the terms and techniques (they are not always the same) and present a historical perspective of their use. If these terms have left you scratching your head in the past then stay tuned, in a few weeks you will be able to walk into a gallery and say “yes, the filigrana vase is nice, but that reticello plate is just stunning.”


16th century incalmo plate,
unknown artist.
The first technique we will focus on is called ‘incalmo’. The name, in Venetian dialect literally means “graft” as in joining two plants. That is a pretty good description of how this effect is achieved; think of a vase whose bottom-half is one color and top is another. The glass artist blows two separate bubbles of glass, opens them and joins them together to form a single bubble. It is a difficult operation because the two open lips must be exactly the same size to join properly. The process can be continued to add more colors; virtuoso pieces may include several sections, each a different color. In addition, the position of the iron rod that the artist uses to hold the bubble can be changed while the piece is under construction, leading to asymmetrical effects.

The above description is the classical way of achieving incalmo, but modern materials and equipment allow artists to achieve a similar effect with considerably less skill. For instance, precise diameter glass tubing is now available in a wide variety of colors. This can be cut into rings with a saw, then stacked in a kiln and fused together. From there, this “prefabricated incalmo tube can be worked by traditional methods. Whether or not this meets the definition of true incalmo depends entirely on whether one focuses on the method or on the end result.


9-10th century incalmo vase,
Syria or Iraq.
The name ‘incalmo’, was applied to glass in the first half of the twentieth century by the Venini factory on Murano, in Venice. [1] However, both the word and the method are much older. The Venini artisans revived the technique to great acclaim, but Venetian examples date from the sixteenth century and Islamic examples from ninth century Syria have also survived. It is not hard to imagine that this joining technique was experimented with shortly after glassblowing became common around the first century BCE. However, what is truly amazing is that any of these early examples survived to be sold to customers without breaking in the cooling process. The reason for this is a technical issue that we have not discussed yet.

All glass expands a little when it is heated and shrinks when it cools. Different formulations of glass generally expand by differing amounts. When a single piece incorporates more than one type of glass, and the thermal expansions differ significantly, the result is disaster. After the piece is finished it is placed in a kiln where it slowly cools back to room temperature. Because of the mismatch, one area wants to shrink more than the adjacent area and the glass cracks along the join. The expansion and contraction is microscopic, but it is enough to ruin hours and hours of work, leading to much gnashing of teeth the morning after, when the finished work is inspected. 

The Venini glass masters had the benefit of this knowledge, but for earlier artisans, trial and error must have played a big role in determining which formulas were compatible. Different colors mean different metallic additives and to match expansion other ingredients would need to be adjusted. Today, manufacturers produce glass in a series based on expansion; artists can be relatively sure that two different colors from the same series can be “grafted” and not self-destruct when cooled.

[1] I have not absolutely confirmed this, but authoritative secondary references credit Venini, and I can find no mention to "incalmo" as a glass technique prior to the twentieth century.

Wednesday, February 18, 2015

The Duke's Oil

Trajan's Column, Rome
Giovanni Battista Piranesi (1758)
In the seventeenth century, alchemy was a dangerous business. Yes, there were risks of sanctions by the authorities, which could be very harsh, but great dangers also lurked in the chemicals themselves. Some like lead and mercury accumulated in the tissues slowly, over a period of years, others could kill a man within a few minutes. Cardinal Francesco Maria del Monte had personal knowledge of just how deadly the products of alchemy could be.

In Rome, Del Monte was the unofficial ambassador to Florence and the Medici family. He regularly greeted dignitaries from around Europe and dazzled them in his sumptuous palace. He was an avid glass collector, a patron of the arts and more quietly a dedicated student of alchemy. He was a lifelong friend to Don Antonio de' Medici and visited the prince's laboratory in Florence several times. This is where Antonio Neri was making glass early in his career. Later, Neri worked at a secondary Medici glass furnace in Pisa, where the cardinal had fancy glass table service made for the Vatican.

About a two mile walk from Saint Peter's Basilica, over the Tiber River, directly toward the Colosseum, is Trajan's Column. It commemorates Emperor Trajan's victory in the Dacian Wars at the beginning of the second century. It displays a scroll in base relief that winds all the way from the pedestal to the capital. The monument is large enough to contain an internal staircase leading to an observation platform at the top. In 1587, it was crowned by a bronze statue of Saint Peter that still stands today; the initial model was sculpted by artist Tommaso della Porta, who was under the patronage of Cardinal Del Monte. 

Giovanni Baglione picks up the story in his book Lives of Painters, Sculptors and Architects:
That man [della Porta], I think, suffered mentally and it showed at the end of his days. When he felt some kind of tingling in his abdomen, he went to the Cardinal del Monte his friend and master and asked for some of the "grand duke’s oil" that he hoped would relieve the tingling. The Cardinal indulged him; gave it to him and said that he should apply it only to the wrists and only a little, because the oil was potent and it could make him feel sick. He took it and went back to his house and after dinner he sent for the barber, to administer the medication, and while the messenger went on, Tommaso impatient and simpleminded, applied the oil himself and instead of touching the wrists, as the Cardinal had instructed, he lathered the arms, chest, body and entire abdomen, so that the powerful oil went to the heart and in fact killed him. The barber arrived to medicate him, found him dead and all attempts at revival were in vain. Tommaso della Porta, was buried at Santa Maria del Popolo.
The "grand duke's oil," was widely known, and widely cited in references throughout Europe well into the 19th century. Its other name was oil of tobacco – essentially a distillation of almost pure nicotine. In very small doses, it acts as a stimulant of the central nervous system, in slightly higher doses it is a narcotic, even greater, but still relatively small amounts act as a quick and lethal poison absorbed directly through the skin. Ingesting a single pill capsule of typical size full of pure liquid nicotine is more than enough to kill an adult in short order.

This story has one final twist. Antiques dealer Domenico Lupo was one of the men present at the reading of Della Porta's will on 7 March 1607. Twenty-five years later, an inventory of Lupo's assets listed a "small figure half old and half new that is said to be of Prior Ant. Neri," either the glassmaker or possibly his great uncle. 

* This post first appeared here 5 February 2014. 

Sunday, February 15, 2015

Saint Philip Neri

Saint Philip Neri, attr. unknown,
prob. after Giovanni Francesco Barbieri (Il Guernico)
In the final quarter of the seventeenth century, a certain holy man in Rome practiced charity in its humblest form. A native of Florence, a man named Filippo Neri (1515-1595) made visits every day to plague victims in the hospitals. He prayed for patients in their last hours and brought food for those abandoned by their families. He walked among the poor and destitute, eating just from the alms he received. He lived what he preached and set an example of Christianity stripped of pride and envy. In unconventional style, he led walking tours of the churches in Rome. Although the practice of venerating the living as saints received strong discouragement by the Church, Filippo Neri nevertheless realized effective sainthood during his lifetime. His followers credited him with numerous miracles.

Conventional history places the exact location of Filippo Neri's birth in Florence on the south side of the Arno. However, local folklore suggests an alternate location: in one of two rooms of the same Borgo Pinti house later owned and occupied by Antonio Neri's family. The common family name of Neri naturally leads to the question of whether or not the saint and the glassmaker were of common ancestry. Antonio's father, Neri Neri, maintained that his own father, Jacopo, was a cousin to the holy man.


A full-length image of Filippo Neri himself appears in a corner of the Neri chapel, On Borgo Pinti in Florence. Giovanni Cinelli, writing in 1677, tells us of Neri di Jacopo (Neri Neri):

It was his intention to dedicate [the chapel] to his relative Filippo Neri; it is possible that Jacopo di Neri, father of M[esser] Neri Neri was the cousin of Filippo Neri then still living, today Saint Philip. But [the dedication] was not to be, because in pressing to oversee its completion and delays in the canonization of the Saint, the dedication was changed to Nereo and Achilles, which was finished by Alessandro per the will.
Because the canonization was delayed, it would have been inappropriate to dedicate the chapel to Filippo, so two of his favorite saints were substituted.

The assertion that Neri the medical doctor and Neri the holy man were true blood relations has yet to be verified. However, there are positive signs: the saint's well-established genealogy meshes with records of Antonio Neri's family housed at the state archives in Florence. In fact, both sets of records—of the alchemist and of the saint—share a single file in the archives. These documents indicate a common ancestry at the level of third cousins. The elder Jacopo Neri and Filippo Neri (later Saint Philip) appear to have shared a great-great-grandfather. It is a remote connection, but one that was a source of  pride for Antonio’s father.


There is also a notable similarity of family crests; the shield of Saint Philip Neri's family feature three stars on a blue field, that of Antonio Neri's family features  a  banner with three stars against a blue rampant lion. The Saint's genealogy is well established, but the matter is complicated in that Antonio's branch of the family left Florence around the start of the sixteenth century. Here we lose track of them for one generation. Regardless of the difficulties, there is mounting evidence that Antonio's fourth-great-grandfather, Michele di Neri, was the brother of Saint Philip's second-great grandfather Ser Giovanni di Neri. A further association with Filippo Neri lies with Antonio Neri's maternal grandfather, Francesco Parenti, who served as attorney for the saint’s sister Caterina in the execution of the holy man's will.


Filippo Neri was unusual for his time. He was a champion of the common man, and he was humble to a fault; not a leader by force, by wealth, nor by charisma, but by gravitas. Antonio Neri's father seems to have been a man from the same mold, as exemplified by the absence of self-import declarations or artifice. He admired Filippo Neri, and we can guess that he shared the holy man's philosophy. Filippo never wanted  and protested strenuously against any aggrandizement. We see this trait follow through with Antonio. In his manuscripts and in the book on glassmaking, there is no evidence of boasting, or name-dropping, nor claim of superiority. What we see is a humble quest to understand nature, and to be of service to mankind.


* This post first appeared here on 3 February 2014
.

Friday, February 13, 2015

Iron into Copper

The recovery of copper from vitriolated waters,
from De Re Metallica, 1556, by Agricola (Georg Bauer).
In Discorso, one of the last manuscripts written by Antonio Neri before his death, he reveals several transmutation recipes. One describes turning iron into copper; it is instructive because it uses common materials that we can identify and because the chemistry is now well understood.

Take some iron sheets and lay them in vitriol water, being immersed in that, they will rust. Scrape off this rust, which will be a red powder, melt it in a crucible, and you will have perfect copper. The same effect can be had from various waters that are naturally vitriolated, because they flow through mines of vitriol, such as those of a source some distance from Leiden, and another below the fortress of Smolnik, [now in Slovakia].

Vitriol is an acidic sulfate dissolved in water, it could be made in the laboratory, but it also occurred naturally around mining operations where sulfurous minerals were present. Alchemists knew this solution as "oil of vitriol" and "spirit of vitriol." The mine that Neri references in Smolnik became famous for transmutation. As late as the eighteenth century, scientists and experimenters from around Europe made the pilgrimage to see the effect for themselves and tried to figure out what was happening. It may be a surprise to some readers, but following the above instructions will, in fact, produce copper just as Neri claimed. There is no deception or sleight of hand involved; the explanation is straightforward, but first, Neri treats us to a rare glimpse of his own reasoning on the subject:

Some estimate and not without reason, that this experiment, being used to prove the transmutation of metals, is not suitable for this purpose. They say that the vitriolated waters become such because they are already heavy with the corrosive spirits of sulfur, having passed through the copper or iron mine, these waters corrode copper in the same way aqua fortis corrodes silver. So that really the substance of the copper remains in the water, which attacks the surface of the iron, which always remains iron. However, if that were true then the iron would not get consumed, or if it were consumed it would mix with the substance of the corroded copper in the water, and if it were fused, it would remain a mixture of iron and copper. And yet in this experiment, all the iron is consumed; it is reduced by the vitriolated water into powder, […] which in the fusion is still pure copper, so there should remain no doubt that this is a true transmutation.[1]

Given the state of chemistry at the time, Neri's reasoning is clear and rational. The iron disappears and a copper coating materializes in its place. What better evidence of transmutation could one ask for?

The key to what was actually happening is in the criticism leveled by skeptics. It turns out that they were on the right track, but neither they nor Neri had the full picture. Today, we understand it as a simple ion exchange reaction; blue vitriol water is a transparent saturated solution of copper sulfate (CuSO4), in the presence of solid iron, the liquid dissolves the iron; copper from the vitriol is deposited in its place. The two metals, copper and iron, change places: the iron dissolves, forming green vitriol (FeSO4) and copper is expelled from the solution. The result is a reduction in the amount of the iron, which is replaced by a proportional deposit of pure copper.

On a physical level, this chemical reaction is no different today than it was in the seventeenth century. What has changed is our interpretation of the experiment. What Neri viewed as a transformation of iron into copper, we now see as an exchange. There is, however, a deeper lesson in all this. As an alchemist, Antonio Neri was not being delusional or dishonest; he was careful, observant and applied his knowledge as best he could. This is no different from the way science works today. Both then and now, to be successful in unraveling nature’s secrets, one must become accustomed to a very uncomfortable situation: In the past, careful reasoning by brilliant thinkers has led to utterly wrong conclusions. The fact that much of our world is a mystery is unsettling; that the very process we use to understand it can be so flawed is harder to accept. Even more difficult is that the faculty we all rely on for survival—our own wits—can lead us so far astray.[2]

[1] For more, see Discorso sopra la Chimica: The Paracelsian Philosophy of Antonio Neri”, M.G. Grazzini / Nuncius 27 (2012).
[2] This post first appeared here on 31 January 2014.

Wednesday, February 11, 2015

Caterina Sforza

Caterina Sforza, by Lorenzo di Credi
(now in the Museum of Forlì.)
Antonio Neri is remembered mostly for his book on glassmaking, L'Arte Vetraria. However, he considered himself first and foremost an alchemist. This interest can be traced to at least two generations before him; his father, Neri Neri, was an acclaimed physician – in fact, the personal physician to Grand Duke of Tuscany, Ferdinando I de’ Medici. Antonio's grandfather, Jacopo Neri, was a barber-surgeon. Both of these professions required an extensive knowledge of herbal distillation and other techniques which are shared by alchemists.

Antonio's benefactor, Don Antonio de' Medici, also followed a family passion for the chemical arts, in his case, traceable through an unbroken chain, to a female alchemist, his great-great-grandmother, Caterina Sforza, (c.1463–1509). After her death, over four hundred of her formulas were passed down to her son, Giovanni dalle Bande Nere, then to his son Grand Duke Cosimo I de' Medici, Grand Duke Francesco I, and finally to Don Antonio. 

Caterina was the illegitimate daughter of the Duke of Milan, Galeazzo Maria Sforza, but was still educated at court. At age fifteen, she was married to a nephew of Pope Sixtus. The pope granted her title of Countess of Forlì and Imola. After her territory was later taken and her husband murdered (by a faction of their own people), she escaped prison and retook the two cities. In 1495, when her second husband was assassinated, she launched a campaign which gutted the families of the murderers. Her third husband was Giovanni de' Medici, and their son, named after his father would become a brilliant military strategist, like his mother. His own son, Cosimo, would later become the first "Grand Duke" of Tuscany. 

Her chemical recipes were transcribed in 1525 by a captain in her son's army, Count Lucantonio Cuppano da Montefalco, and ultimately published as a book in 1893 (Passolini). Included are an assortment of formulas which range from cosmetics, to medical remedies, poisons and alchemical concoctions.
Researcher Jacqueline Spicer writes:
Lost among the romanticized military conquests is a thorough account [of] the project that occupied several years of her life—the manuscript of her alchemical and medical experiments and recipes titled Gli Experimenti de la Ex.ma S.r Caterina da Furlj Matre de lo inllux.mo S.r Giouanni de Medici, or Gli Experimenti. The text is an early example of what would later become the popular medical genre of "Books of Secrets", but is so early that it does not appear in most modern writing on such books. Furthermore, Gli Experimenti is unusual because it was written by a woman in an otherwise male dominated genre, and unique in that we know a great deal about the life of its author.[1]

Among the alchemical entries are "to convert pewter into silver of the finest quality and of standard alloy," a method "for giving to bars of brass a fine golden color" and another for "for multiplying silver." Also, there are ways described  to "make iron hard," "to dissolve pearls" and "to dissolve all metals." In the medicinal category, we find "for infirm lungs, an ointment is to be made of the blood of a hen, a duck, a pig, a goose, mixed with fresh butter and white wax." This was to be applied to the chest with a fox's skin.
Sandro Botticelli, Primavera (1498)
(detail - rightmost of the three graces)

Caterina Sforza was painted many times and often depicted as the Virgin Mary, a typical trope for the nobility at the time. She may have been immortalized  by Sandro Botticelli as the rightmost of the three graces in his Primavera and as the main subject in The Birth of Venus.[2] Reportedly, she was the subject of ballads and sonnets, although most have been lost. She is a topic of discussion in Niccolò Machiavelli's famous treatise The Prince

In the end she was captured, raped and imprisoned on the orders of Pope Alexander VI, who justified her incarceration, in the Vatican's  Sant'Angelo Castle, by claiming she tried to poison him. She survived the ordeal, but after release entered the convent of the Murate nuns in Florence, and died, in 1509, at the age of forty-seven. She was buried at the convent, in the same city where her future great-great-grandson, Don Antonio, along with Antonio Neri, would perform their own alchemical experiments and help usher in the age of  modern science.

[1]https://sites.eca.ed.ac.uk/renaissancecosmetics/cosmetics-recipes/caterina-sforzas-experimenti/ also see  http://edinburgh.academia.edu/JacquelineSpicer.
[2] Another possibility for the model of Venus was Simonetta Vespucci.
This post first appeared here on 27 January 2014.

Monday, February 9, 2015

Botanical Gardens Reprise

Rudolf II as "Vertumnus"(c. 1590)
Giuseppe Arcimboldo.
In 1543-44 new botanical gardens were founded in Pisa; L’Orto Botanico was its Italian name. It was the very first garden devoted to the research of plants. Literally within a year, similar gardens sprung up in Padua and Florence, and many other cities followed shortly thereafter. Exotic foreign species as well as important local plants were grown, studied, harvested distilled, and imbibed. These horticultural stations became centerpieces of medical programs throughout Italy, and then greater Europe. The concept of herbal (“simples”) gardens was centuries old. Almost every monastery, convent and hospital maintained a space to grow the plants they needed to transform into medicines for care of the infirmed. The grafting of fruit trees was actively practiced since before Roman times, but these new gardens were specifically planted as research spaces and run by universities. 

When Neri Neri, the father of glassmaker Antonio Neri, studied medicine at the Studio Fiorentino  in the mid 1550s, there can be no doubt he spent time at the gardens in Florence, and quite possibly at the ones in Pisa. (The Pisa gardens were moved twice before arriving at their current location in 1591). This was a period of vigorous expansion in the field of herbal medicine. Competition was fierce to obtain and study medicinal plants from around the globe. Cosimo I de’ Medici poured money into the medical school in Pisa, attracting students and faculty from around Europe. In 1554 famed botanist and physician Andrea Cesalpino took over the Pisa gardens  from his teacher, Luca Ghini, who first built them. 

In 1602, Neri was to be found working alongside Niccolò Sisti at the grand duke’s secondary glass furnace along the Arno River in Pisa. According to Neri’s own account, Pisa is where he worked on ferns as an alternative plant salt for glass and mentions many other plants with which he experimented: 
Set about making ash in the way previously described, however use the husks and stalks of broad beans after the farmhands have thrashed and shelled them. The same may be made from the ashes of cabbages, or a thorn bush that bears small fruit, called the blackberry, even from millet, rush, marsh reeds, and from many other plants that will relinquish their salt.
In a letter to Neri from his friend Emanuel Ximenes, the Antwerp based Portuguese banker expressed surprise that Neri was able to devise a fern based glass salt recipe so quickly. In all likelihood, Neri would have had access to the botanical gardens and the small adjacent laboratory located just a few blocks from the glass furnace. In the period of time the glassmaker spent there, the directorate of the gardens changed hands from Francesco Malocchi to Marco Cornacchini. Both of these men avidly pursued new botanical based cures, and corresponded internationally. 

In his Glassmaking book, L’Arte Vetraria, Neri devotes a number of recipes to making paint pigments from flower blossoms. While he could have easily obtained his stock material from any number of sources, the botanical gardens would have certainly provided a convenient cache of many different varieties.

In the winter of 1603-4 Neri traveled From Pisa to visit his friend in Antwerp. If he followed Ximenes suggested route, he would have passed back through his native Florence, then on to Venice where he would meet up with a caravan of merchants on their way to the Frankfort spring fair, and then on to Antwerp by river. Upon his return to Italy, seven years later, he wrote his glassmaking book, but then devoted himself fully to alchemy and medicine. In January of 1614, in what might be the very last manuscript he worked on before his death, he wrote about some recipes “copied from an old book here in Pisa.” At that time, the director of the botanical gardens was Domenico Vigna, who continued to direct the gardens on and off until 1634.

It would be interesting to know how Neri the alchemist thought about his raw materials. Did he see all the possibilities of what could be made with them? For instance, how did he approach a towering pile of May ferns, large enough to produce a hundred pounds of ash, or a giant sack of rose petals? Did he ever lean forward and breathe in the delicious musty aroma? Did he ever dig in with his hands and bury his face in an arm-load of soft, pure color? How could he not?

*This post first appeared here 22 Jan 2014.

Friday, February 6, 2015

16-17th Century Glass Furnace

From "De re metallica" 
Agricola (Georg Bauer) 1556.
In the seventeenth century, glass furnaces represented a pinnacle of technology. True, the ability to achieve the high temperatures required to melt glass had been around for centuries – high enough to melt gold, silver and copper as well. What made the glass furnace remarkable was its refinement. It made efficient use of its hardwood fuel and was able to maintain a controlled, even temperature long before any thermometer could measure it. In fact, Galileo was only just beginning to use glass bulbs and tubes to measure differences in ambient room temperatures.

In Florence, the construction used was typical of the time throughout Europe, called a "beehive" furnace because its shape resembled the elongated dome of a beehive. A double wall, built of fire resistant bricks, provided further insulation, trapping heat inside. Vertically, the furnace was divided into three levels, each forming a wide open chamber. The bottom space was used to build the fire, and had one or two openings to the outside, used to add wood fuel, rake the coals, or shovel out ash. The second, central level was where the pots of glass resided. A central hole or "eye" on the floor directly exposed the fire pit below. The space directly next to the eye was the hottest, and temperature could be further controlled by moving the crucibles farther away or closer to the eye. A number of openings in the wall allowed gaffers access to the glass pots, and at least one larger opening was used to place new crucibles, or rearrange the existing ones. The upper chamber was used to control the draft, and sometimes for annealing. Again, a central hole in the floor of this (top) level allowed exhaust gasses to leave the glass chamber and an opening to one side vented the exhaust.

In his book, L’Arte Vetraria, Neri is careful to stress that only dry oak or other hardwood should be used because it burns cleanly, and will not deposit ash or creosote in the glass.
The furnace should have dry wood, hard wood of oak because soft wood tinges the furnace and does no good. Stoke it steadily and continuously so that the flame is always clear, and there is never any smoke, which is very important in order to make a beautiful cristallo.
Once a finished piece of glassware is made, it must be allowed to cool slowly, over a period of many hours. This was often accomplished by building a long enclosed horizontal trough that connected to the furnace. A draft opening at the far end allowed heat from the furnace to be drawn in, and finished pieces were placed in a pan at the furnace end and then slowly pulled by a chain further and further down the trough toward the cooler end. This "annealing" process ensured the glass would not develop stresses and crack as it cooled.

Although Neri does not concern himself with the vagaries of furnace construction in the book, it is clear that he did possess considerable knowledge on the subject. Several of his unconventional methods for making pigments for glass involve taking bricks out of the furnace wall to stash chemicals for long term exposure to the heat.
Take small pieces of copper and put them inside the arches of the furnace. In that place, they will be within the walls. Leave them that way until each piece of copper is well calcined, using a simple fire.
While it is true that artisans of the early seventeenth century did not possess the same understanding of nature that we now enjoy, they did have a working knowledge that served them very well. It was backed by a theoretical framework that was quite sophisticated and was consistent with what could be observed and measured at the time. This is no different from our own modern understanding of nature: sophisticated and consistent with what we can observe and measure.

*This post first appeared here 24 January 2014

Wednesday, February 4, 2015

Like Snow From Heaven

28th December 2005 in Florence
Photo by Marco De La Pierre
In its simplest incarnation, glass is nothing more than crushed quartz or sand mixed with glass salt. This salt is the carbonates of sodium or potassium. Essentially, plant ash oxidizes in the furnace and dramatically lowers the melting point of the sand.

In Pliny's account of the discovery of glass, the process takes place in a single step. The ingredients came together accidentally in a fire and "glass trickled out." The problem is that pure quartz does not react with the salt until it gets very hot and even then, it does so reluctantly. In a wood-fired furnace, quartz stones, even small pebbles or sand would melt with excruciating slowness. As Neri advises, "... this would only succeed after a protracted period of time and a great amount of trouble." 

'Fritting' is an intermediate step that speeds the process considerably. Glassmakers reduce the quartz to a fine powder and then mix it with alkali salt. In the heat of a kiln, the entire content of each stone is thus exposed to the salt right from the beginning. This roasting process starts a chemical reaction between the ingredients. The combination is then cooled and 'aged' for several months before use. When made from pure quartz river stones and the best Levantine ash, the result is what Neri calls 'bollito,' "white and pure like snow from heaven."

A third ingredient of glass, critical to its long-term stability is lime, or calcium oxide. Without the lime, glass is susceptible to attack by water. The water actually dissolves the glass, or less dramatically makes it subject to 'glass disease' or 'crizzling', a condition where the glass slowly decomposes due to humidity in the air. Waterglass is a product made without the lime. On Murano and elsewhere, it was painted onto the shells of eggs to seal and preserve them. In Neri's era, lime was produced by roasting seashells. It was a key ingredient of cement, and as such was readily available. It had been a major commodity throughout the Mediterranean since the Roman Empire. Neri advises to add lime to all his glass recipes, but it is not so clear that he himself understood why it was so important.


*This post first appeared here on 11 October 2013.

Monday, February 2, 2015

The Golden Sun Reprise

The Sun, Robert Fludd
from Utriusque Cosmi (1617),v. 2, p. 19.
Today, Antonio Neri is best known for his 1612 book, L'Arte Vetraria, in which he exposes the secrets of the art of making glass. In publishing his volume, he helped to fuel new discoveries in chemistry and medicine simply by making glass apparatus more available to experimenters. A 1662 translation of his book into English was one of the first acts undertaken by the newly formed Royal Society in London. Neri himself lived for only two years after his book went to press, in his native Florence, and never saw the seeds of his labor come to fruition. If he had lived, he might well be surprised that his legacy is in glassmaking, and not in the subjects that he himself held most dear.

In his death at the age of thirty-eight, Neri missed a rapid advancement in our basic understanding of nature. In the space of only a few decades the face of science and medicine would start to change irrevocably. Soon, experimenters were finding new chemical elements and began to map out the periodic table, often with apparatus made of glass. For centuries, the ancient Aristotelian concept of air, earth, water and fire as the basic building blocks of the universe had endured. By the end of the seventeenth century, the inadequacies of the old model were becoming clear. 

But Neri was not privy to any of this. In his time, any cracks in the Aristotelian model were minor. Like his sponsor, Medici prince Don Antonio, Neri was an adherent of new doctrines of the physician Paracelsus, who rebelled against the old system, but was still very much a product of it. First and foremost, Neri thought of himself as an alchemist. While history has not generally been kind to his ilk, a true understanding of early modern science rests on the methods and reasoning developed by alchemists like Neri. 

Although alchemy covered a wide range of activities, it will forever be associated most closely with the mistaken notion that base metals such as lead or iron could be transmuted into gold. Once science had established this idea as specious, the race was on to separate "new science" from the old. It became fashionable to cast alchemists into the mold of charlatans, tricksters and self-deceived fools. While many such characters did exist, Neri was not one of them; his work was based on careful reasoning and experimentation. The final irony is that through the kind of advancements that he himself helped to pioneer, the majority of his life's work has fallen by the wayside. What has endured the test of modern science is his treatise on glassmaking.

As early as the age of twenty, Neri was demonstrating transmutation to expert gold refiners. As late as the year before his death he was writing authoritatively and coherently on the subject. To understand how this is possible – to be rational and methodical, and at the same time completely wrong – is to get a sense of the true difficulties involved in science. Based on what he was taught, what he read, and his own experimentation, Neri thought metals and other materials "matured" over time. He thought that more "imperfect" metals like lead and iron were part of a continuum that ended with the "perfect" metal gold. Furthermore, he thought that primordial "seeds of gold" left over from the creation of the earth could be mined and isolated. Like wheat and other plants, given the correct nurturing, and conditions, this seed material could be encouraged to mature into vast quantities of gold. Writing in his 1613 manuscript Discorso, he says,
The response is that the chemical art lets the gold proceed from that present and immediate cause, because this is the seed of gold, which acts naturally when art cooperates. The chemist does nothing but extract the seed from gold and apply it to suitable bodies, with which it is united to render the fruit multiplied in the same way that the farmer does. He does not produce the fruit, but provides and prepares the earth and the seed, uniting them in such a way so that they bear fruit.*
Neri thought that ultimately, for gold transmutation to be successful one needed the blessing of the Creator. He documented his process in a heavily coded (and incomprehensible) recipe he called "Donum Dei" (the most precious gift of God). This name traces to alchemical writings from as early as the fifteenth century. He maintained that those who might harm society with this knowledge or wished to profit personally or swindle others would be denied the blessing and therefore be unsuccessful. 

The remarkable thing here is that Neri's understanding of chemistry was supported at every turn by experimentation. His recorded methods, for transforming lesser metals into one-another, were repeatable and stood the test of scrutiny by contemporary experts. In the light of modern chemistry, these transformations depended on subtle physical processes and chemical reactions that would not be understood for another century or more. By performing these experiments under controlled conditions, he was taking the first steps in what would become modern science. Eventually, it would be understood that while chemical compounds can be created and destroyed by various manipulations, individual elements cannot. Today we know that iron, lead and gold were formed in the cores of ancient stars, not too different from our sun. Lighter elements are successively transformed into heavier ones under a star's "nurturing" conditions. While he lived in a period in which he had no chance of getting the particular details correct, in a poetic sense Neri was not far from the truth.



* See Maria Grazia Grazzini, “Discorso sopra la Chimica: The Paracelsian Philosophy of Antonio Neri” Nuncius 27 (2012) 311–367.