Chalcedony Glass

17th century ribbed bottle,Brescia, Italy.

In hopeful anticipation of flowers, the cusp of spring seems the appropriate time to celebrate Antonio Neri's most colorful creation; chalcedony glass.[1] Through his clever technique, the 17th century glassmaker and alchemist managed to throw every color he knew into one glass pot and come up with, not mud, but the opposite—a swirly rainbow glass that defies verbal description. Somehow, he achieves a balance that blends a full range of colors in a way that seems natural and harmonious. While many glass creations survive from the seventeenth century, none is directly attributable to Neri's glass formulation. But, in my opinion, this piece from Brescia comes close to our alchemist's own description. 

Chalcedony is one of the more exotic varieties of glass described in Antonio Neri's book, L'Arte Vetraria. It is also one of the most labor intensive, exacting recipes and consequently a 'high stakes' risk for losing the entire batch after considerable work. Nevertheless, Neri assures us that the end result is worth the trouble; he describes it as:

Adorned with so many graceful and beautiful areas of undulations and enhanced with the play of diverse, lively, flaming colors.

Chalcedony is a natural mineral, known and admired since antiquity. It occurs in a variety of translucent colors and is most valued when swirls of many different colors are present together in the same piece. In the Roman Empire, it was prized for seals and signet rings; its fine-grained structure allowed intricate carving without fractures. Like many other rare natural materials, it was sometimes supposed to have mystical healing properties. 

Chemically, the mineral chalcedony is identical with quartz or silica, the main ingredient of glass. However, unlike the fabricated substance, the mineral is formed of networks of microscopic interlocking crystals that are responsible for its favorable properties. Small amounts of impurities between the crystal grains cause the swirls of color.

Neri presents three variations of chalcedony glass that span his career as a glassmaker. The first he describes as "the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there." The last was made "in the Flemish city of Antwerp, in January of the year 1611" where he presented "His Excellency, the Prince of Orange with two vessels of chalcedony [glass] which delighted him greatly."

His friend Emmanuel Ximenes was anxious to learn the secrets of this glass as early as July of 1603, when he wrote: 

The details of the last chalcedony [glass], which you promised to send to me, did not come in the letter: but I had to recant by the time I got to the end […] I see and understand, that Your Lordship is not at leisure, but in fact busy at work in the service of Christianity... 

Neri advises that in order to bring out the swirls of color, the glassblower must cool and reheat the piece several times, a process that today is known as 'striking'.

Unfortunately, there is also a dark side to this colorful creation.  It is strongly advised to avoid replication of Neri's chalcedony glass as described in his book of recipes; it contains a cocktail of extremely toxic ingredients. While these are relatively harmless once locked inside the glass, in preparation and especially in the hot molten glass melt, vapors of mercury and arsenic can be deadly. Moderate exposure can be expected to cause neurological and liver damage. (The term "mad as a hatter" comes from the unfortunate side effects of inhaled mercury vapors in the formation of felt hats.) In addition, Neri's extensive uses of strong acid reactions in these preparations make sudden eruptions and severe chemical burns a very real danger.

[1] At least in the northern hemisphere, lets say "autumn colors" in the south.
*This post first appeared here in a slightly different form on 27 September 2013.

Rise and Fall

"Merry Company," (1623)

Gerard van Honthorst

The first decade of the seventeenth century was a golden era for glass in Tuscany. The Venetian techniques brought to the region by Grand Duke Cosimo de' Medici in the 1570s had been assimilated. The pioneering work of his son, Francesco, in cross pollinating different crafts under one roof, was by now bearing fruit in unique items that included the handiwork of glass artisans. Grand Duke Ferdinando understood the value of glass as a source of prestige and was willing to invest in it. This was the environment in which Antonio Neri first learned to make glass. Delicate drinking glasses were the toast of the aristocracy throughout Europe. The material was critical to the advancement of chemistry, medicine and by the end of the decade astronomy. 

In 1602, Antonio Neri came to work in the shop of Niccolò Sisti in Pisa. While Sisti was making fancy glassware for the Medici court, the nearby Coscetti firm was supplying Pisa with everyday items. Coscetti made glassware for private homes, but also innkeepers, spice and perfume sellers, winemakers and a baker among others. Their wares included cruets for oil, saltcellars, carafes, drinking glasses, containers for holy water, reliquaries, gilded Venetian style cups and English style flasks. 

By the second decade, momentum started to shift and before long, the glass industry in Tuscany fell on hard times. Apparently the demand for glass could not support the number of factories that had started and the rapid succession of leadership in the duchy added uncertainty to patronage of the arts in general. 

Another factory in Pisa was run by Giovanbattista Guerrazzi, who had acquired the exclusive right to make Venetian style cristallo from Neri's old employer Sisti. In 1623, Guerrazzi had problems of a different sort, not directly related to the sales of glass. He appealed to Pisa’s Office of Rivers and Ditches, pleading with them to modify a recent ruling. He explained that he owned three houses next to his furnace, one for his family and the others functioning as sales space and housing for his workers. Since he was the exclusive maker of cristallo, he had employed a number of girls and women to decorate the delicate glassware, and a constant stream of the nobility showed up to watch the work being done. Guerrazzi's problem was that the Magistrate of Public Decency had recently published a list of seven places where women of "ill repute" were allowed to stay. One of these was located next door to his glassmaking operation. He begged for a change in the ruling, to move his new neighbors elsewhere.

The outcome of his appeal is not known, but Guerrazzi was succeeding in the glass business, and at the same time accelerating the demise of his competitors. He bought-out and demolished the furnaces of a number of other glassblowers and planned the same fate for the Coscetti operation, putting all the craftsmen there out of work. In the mid 1620s, after a quarter century of operation, the fires under Coscetti furnace were allowed to go out forever. Furnaces at Leghorn, Pistoia and Prato had shuttered, leaving only the one furnace in Pisa, two in Florence and two at the castle of Montaione. 

*This post first appeared here on 12 Dec 2013.

Sisters of an Alchemist

Portrait of the Egerton Sisters
(no relation to Neri)
English School,  c. 1601-1602

Among the ten children born to glassmaker Antonio Neri’s parents, three of them were girls; Lessandra, Maria, and Lucrezia. Because women were not allowed to legally own property, or sign contracts many of the usual sources of information are silent. Most of what we can learn about them is through their relationships with the men around them.

The Neri's were a patrician family, and the children enjoyed a very comfortable existence for the late sixteenth century. There is evidence that all three sisters survived into adulthood. Lessandra was the first-born, nine years older than Maria, and twelve years older than Lucrezia.

When Lessandra was around age seventeen, her famous father, Neri Neri, was appointed as personal physician to the newly crowned Grand Duke Ferdinando de’ Medici. However, only a few short years later their mother Dianora died at age 42, of causes that are unknown, perhaps childbirth. The girls were 22, 13 and 10. A few short years later they lost both their father, and a brother.

Two information sources for the Neri sisters are their birth records kept at the Opera del Duomo and genealogy records for the family which are filed at the National Archives, both in Florence. The baptism records hold a wealth of indirect material through the names of their godparents. While these do not tell us anything specific about them, it does tell us who their influences were; who they looked to for strength and spiritual guidance, under the circumstances, this is the best we can do.

Lessandra (b. 1572) claimed Baccio Valori as her godfather. The Valori family had a long, tragic history with the ruling Medici family. His father, grandfather and great-grandfather were all close Medici supporters, yet each ended up exiled, imprisoned, or executed after relationships soured. On one hand he was faithfully employed by the Medici, yet he reportedly spent a good deal of his time collecting letters and papers documenting his family’s close support of Girolamo Savonarola, the firebrand Dominican priest who lead Florence in the late 1490s, after the Medici had been temporarily expelled from the city.

Lessandra’s godmother was Marietta Gaetani, also from a noble family, which included dukes, cardinals and popes. They played prominent roles in the politics of Pisa, Rome and Naples for several centuries. Marietta’s father owned the house from whose tower Galileo showed the moons of Jupiter to Grand Duke Cosimo II in 1610.

The genealogical records imply that Lessandra later took vows with the S. Agata monastery on the North end of Florence and took the name suor Emilia.


Maria’s (b. 1581) godfather was Monsignor Giovanni Alberti. Giovanni was the son of a Florentine senator. He served as protonotary apostolic for Pope Gregory XIII and as bishop of Cortona under Pope Clement VIII. A godfather serving in the papal inner chambers was a good family contact indeed. Also appearing for Maria was Pierfilippo Perini, a physician and lawyer. The Registri lists Maria Neri's godmother as Alessandra di Girolamo Pepi. Among the prominent Florentine republicans was Alessandra's father, Girolamo. He was tortured by Alessandro de' Medici in the 1530s, upon the family's regaining control of Florence after the siege.The genealogy indicates that she married into the Boscoli family, but further work is needed to identify a specific individual.

Lucrezia (b. 1584), the youngest Neri girl, has a single godparent listed in the register, Montiglio degli Albizi. The Albizi family boasted powerful bankers and politicians. This was another case where deep divisions over Medici rule drove a family apart. Perhaps the best-recognized member of the Albizzi family was Eleonora degli Albizi. She was the young consort of grand duke Cosimo I. Folklore has it that in 1566, Cosimo intended to retire from public life and marry Albizi quietly, after the birth of a girl, but his regent son, Francesco I, forbade it to due to the inheritance complications that would ensue. The story is that Cosimo's long-time personal secretary, Sforza Almeni, leaked word of the clandestine marriage to the family. For his betrayal, an enraged Cosimo murdered Almeni in cold blood. Eleonora later gave birth to Don Giovanni de’ Medici, the uncle and friend of Don Antonio, Neri's sponsor. The specific Albizi family member we are interested in, Lucrezia's godfather, Montiglio degli Albizi, seems to have eluded history. Lucretia married into the Talenti family, but no further details are known.

Women in Alchemy

Antonio Neri, 1598-1600,

MS Ferguson 67, f. 25r.

It is certain that women have participated in the practice of alchemy since its beginnings, but hard documentation is scant. Maria Prophetissima, also known as Mary the Jewess, is perhaps the best known female alchemist. None of her writings have survived, but she is thought to have lived around the third century. Legend tells that the "bain-marie" (double boiler) is named after her.

In the seventeenth century, celebrated glassmaker and alchemist Antonio Neri provides us with further detail, even if raising more questions than answers. One of his manuscripts, entitled Tesoro del Mondo (Treasure of the World) depicts three women running chemical equipment. Unfortunately, we are left to guess who they were and what role they played in the larger Florentine technical arts community. It is possible that these were nuns, trained in the same Church sponsored educational system that produced Neri. Convents were often expected to be self-sufficient and many ran their own pharmacies. Neri had sisters as well as brothers and at least one sister entered a convent located on the north side of Florence, near the laboratory where Antonio practiced alchemy and made glass. The fact that specific names have not been associated with Neri’s three female co-workers should not deter us from celebrating their contribution to the birth of early modern science.

Within a year of his ordination in the Catholic Church, Neri began an ambitious treatise, illustrated in his own hand, devoted to "all of alchemy." Six of the illustrations in this manuscript, completed in 1600, show women tending equipment. It is not remarkable that some alchemists of the 16th century were women, what is remarkable is to find them in the historical record. Direct depiction of female participation in alchemy is otherwise extremely rare. 


Two pictures in the Neri manuscript show female alchemists at

Antonio Neri, 1598-1600, 
MS Ferguson 67, f. 35r.

work. In both cases, the technician stands behind a dedicated piece of apparatus, facing forward, giving the impression of propriety in an arranged portrait. In other words, Neri is drawing his co-workers at their stations, practicing their art. The first drawing depicts a furnace and vessels used to make liquid mercury from its ore. The other shows a different type of furnace with a 'tower,' used as an efficient way to cook ceruse (white lead oxide). These images are part of a larger set of two dozen similar drawings that each illustrate the equipment used to prepare a specific product, many include a furnace and glassware. Nine of these show a single individual, (or in one case two men) tending the equipment. Because the manuscript is a recipe book, it contains almost no personal information. However, the context of these illustrations indicated that like their male counterparts, the individuals depicted all have specific responsibilities and specializations within the workplace.


Three other illustrations in the manuscript are notable for their engagement of women. These pictures show details of kitchen and nursing work; what might be termed more traditional female roles in the sixteenth century. Two of these illustrations are devoted to the respective arts of preparing plants and animals. They show women working alongside men performing various tasks. A third illustration shows medicinal fogging tents tended by a woman. Inside one tent, a male patient sits naked on a bench, exposed and breathing fumes pumped in by a large vessel perched over a fire. Similar arrangements are known to have been used to treat skin lesions caused by leprosy and syphilis.

Antonio Neri, 1598-1600, 
MS Ferguson 67, f. 37r.

The circumstances in these images present other possibilities to Antonio Neri's work environment. One is that the scenes take place at the Neri household on Borgo Pinti in Florence. Antonio's father was the personal physician to Ferdinando de' Medici, the grand duke of Tuscany. He was also the head of the college of physicians in Florence, and presumably ran a thriving private practice. The women may be Neri's siblings or other family members. 

Another possibility is that we may be looking at operations inside the Casino di San Marco soon after prince Don Antonio de' Medici's occupation of the facility. This palace laboratory had a reputation for medical cures that extended throughout Europe. Don Antonio spent extravagant sums to learn alchemical and medicinal secrets. The glass furnace here, which had employed masters from Venice is where Neri began formulating glass. The presence of women among his colleagues indicates a social setting with a camaraderie not displayed in other alchemical works of the period. 

* This post first appeared here on 17 March 2013 in a slightly different form.

Dianora Parenti

Agnolo di Cosimo 'Bronzino',

"Portrait of Florentine Noblewoman"

(subject unknown , circa. 1540).

The mother of Antonio Neri, the 17th century glassmaker and alchemist,  was named Dianora Parenti. She was the oldest of six children: three girls and three boys. She was born in Florence, on 11 February 1552, with the given name of Dora listed in the city's baptistery register. In all probability by the age of eighteen she was quite accustomed to helping her mother with the other children; Caterina, the youngest, was born less than a year before Dianora's wedding.

Her father and grandfather were prominent lawyers; together they handled much of the personal business of famed artist Michelangelo. On the 20th day of August 1570, Francesco Parenti walked his eldest child down the aisle to be joined, in holy matrimony, to physician Neri Neri. Two years later, their first child Lessandra was born. 

Historians Luigi Zecchin and Enzo Settesoldi identified four of Antonio's brothers, two older and two younger. They were Jacopo (1573), Francesco (1575), a second Jacopo (1577) and Vincenzio (1579). In addition to these five boys, there were at least two more brothers born later, Emilio (1583) and Alessandro (1587). And there were at least three girls, the first-born child Lessandra (1572) and two younger sisters: Maria (1581) and Lucretia (1584). 

In all, there were ten births by Dianora recorded in Florence, occurring almost like clockwork on a fifteen-month schedule. As did many women of the period, she spent a significant portion of her adult life pregnant. In her case, it was a span of sixteen years, carrying one child after another with minimal interruption.

The birth of a child in Renaissance Florence was no small occasion. Patrician families went to considerable expense on decorations, on food and drink for guests and on gifts for the mother and godparents. "The woman who gave birth, like a bride at her wedding, occupied for a passing moment a position of unparalleled honor,"* more than that, while a wedding signaled the transition from daughter to wife, the birth celebration was a rare social recognition of a woman as an individual.

A genealogical record of the eighteenth century, held at the State Archives in Florence (ASF), confirms most of the Neri children's births. It also sets the date of death for their mother Dianora at 1594 when she would have been forty-two years old. This means Antonio lost his mother when he was eighteen and his youngest brother Alessandro was a mere seven.

* Margaret L. King, Women of the Renaissance (Chicago: University of Chicago Press, 1991), p. 4.

This post first appeared on 11 September 2013.

Kitchen Alchemy

Tesoro del Mondo, "Ars Preparatio Animalium"

Antonio Neri 1598-1600, f. 10r (MS Ferguson 67).

Between 1598 and 1600, Antonio Neri wrote a manuscript filled with alchemical recipes. He entitled it Tesoro del Mondo or "Treasure of the World" and stated that it was a book in draft form, intended for publication. It never did see the ink of a printer's press, but Neri's original did survive intact and today occupies a place of pride in the Ferguson Collection of the University of Glasgow Library. [1]

Tesoro is an ambitious work, devoted to "all of alchemy," containing numerous hand-drawn ink and watercolor illustrations; some of the pictures are allegorical, many others document practitioners working with equipment. Only passing reference is made in this manuscript to Neri's later claim to fame: glass—its most notable appearance in Tesoro  is in illustrations of experimental vessels. 1598 was two or three years before Antonio's glassmaking career is thought to have started. His life was busy on other fronts. He had just been ordained as a Catholic Priest, undergoing the laying on of hands ceremony, probably by his neighbor on Borgo Pinti, the Florentine archbishop Alessandro Ottaviano de' Medici. 1598 was also a year of tragedy for the Neri family; by the summer, his father Neri Neri, personal physician to the grand duke, died of an unknown illness, but not before making arrangements for his family, which included a will. A court magistrate would oversee the now orphaned children's education, inheritance and dowries. They would soon suffer further tragedy in the unexpected death of a brother; sixteen year-old Emilio would leave them on Christmas day of the following year, in Castello outside Florence. 

The losses must have been devastating. In 1598, five of the nine children were still under the age of twenty. Without a mother or father, great responsibility must have fallen on the shoulders of the matriarch of the house, the children's elderly paternal grandmother Maddalena. [2] To outsiders, the Neri's were a wealthy and quite well respected family, but internally, the tragic events undoubtedly threw their lives into turmoil. It is in these circumstances that Antonio started his manuscript. The events allude to the reasoning behind a cryptic Latin quote scribbled at the top of a page above the first recipe of Tesoro: "fuimus troes." It means, "We are Trojans no more" From Virgil's Aeneid, referring to the fall of Troy. [3] 

Early in the manuscript there is a series of four illustrations, each showing a different activity, In order, they are titled The Art of Preparation of Stones, Metals, Plants and Animals. [4] Each is filled with multiple workers engaged in various activities pertinent to the specific art. Each highlights interactions between the Aristotelian elements: air, water, earth and fire. There is no specific indication of where any of the four scenes take place, although some educated guesses can be taken. For instance, the stone workers, or lapidaries, almost certainly are an early incarnation of the famed 'Opificio delle pietre dure' working in the Uffizi's Galleria dei Lavori. But we will leave that discussion for another time. 

Of the four illustrations, "Preparing Animals" focuses on activity within a kitchen. (See above, click to enlarge). The scene is intriguing in that it appears to take place in a domestic setting. Labels call out the four Aristotelian elements; birds hanging from the rafters represent air, fish on a grilling rack represent water, a whole carcass on the spit represents earth and fire appears as itself. The scene suggest that this setting is none other than the Neri family kitchen and that the practitioners of the art are three of Antonio's siblings. In the middle right, a young boy is engaged in turning the spit (in green). The best candidate would be then eleven year-old Allesandro, the eventual heir to the family, whose own son named Neri would carry on the family practice as a physician. Of the two young women pictured, the three family choices are fourteen year-old Lucretia, Sixteen year-old Maria and twenty-six year-old Lessandra.

In one sense, the methodology of alchemy lives-on today in kitchens around the world. The process of combining raw ingredients and cooking them together, of experimentation and of iteratively refining a recipe to perfection, this is not so different from what Antonio Neri and his siblings were doing four hundred years ago.


[1] Neri 1598-1600.
[2] Maddalena di Bartolomeo di Niccolò Bartoloz[z]i, married Jacopo Neri, and they gave birth to Antonio’s father Neri Neri. (ASF 599).
[3] Fuimus Troes, fuit Ilium, et ingens Gloria Teucrorum. [We Trojans are at an end, Illium has ended and the vast glory of the Trojans], The Aeneid: Book 2, Line 325.  See also the post in this blog (Conciatore.org) dated 13 June 2014.
[4] Neri 1598-1600, ff. 7r, 8r, 9r, 10r.
* This post first appeared here on 27 August 2014,

Béguines of Malines

A Béguine of Antwerp,

from Pierre Hélyot,

L'Histoire des ordres monastiques… 1719 (v.8)

Five years into his stay in Antwerp, on 21 February 1608, glassmaker Antonio Neri posted a letter to a friend in Florence. The letter was addressed to the house of Zanobi Bartolini—likely the son of Neri’s late former landlord Alamano, also the nephew of Emmanuel Ximenes, Neri’s host in Antwerp. The letter provides strong evidence that however much time Neri devoted to making glass, he also devoted considerable attention to his interest in medicine. 

In this letter, the priest describes his success with medicinal cures. He also references experiments he carried out in Brussels and at the Hospital of Malines, in Mechelen. In particular, he praised Paracelsus’ recipe for ‘theriac of mummy,’ and its superiority to Galen’s ‘theriac magna’. Theriac was an ancient medicinal remedy, often taking the form of a thick honey based syrup. It often contained numerous herbal ingredients. It was thought to be a cure for any poison and used as a way to stave off the plague. Mummy or mumia was a compound composed of just what one might think: the ground up flesh of ancient Egyptian bodies. 

The Hospital of Malines was an ancient one, started in the thirteenth century by a society of lay Catholic women called Béguines. In their 1907 book A History of Nursing, Dock and Nutting note:

Through the whole time of the active career of the Béguines, nursing remained an important branch of their work. One of their most beautiful settlements was at Malines, where there were over 1500 Sisters, not including their dependents. This would appear to have been a nursing center of importance, for Helyot says that the nursing in many hospitals was provided for by orders arising from the Béguines of Malines. […] The building were surrounded with extensive gardens and trees, and had an ample water supply. ‘The sick were nursed there’ he [Helyot] wrote ‘with all the skill, refinement and sweetness that might be expected from the appearance of the place. [1]

The Béguines were not nuns. They did live in communal housing, and did devote themselves to a pious lifestyle, but without formal cloister, without renouncing their possessions, and taking only a temporary vow of chastity, able to leave at any time, for instance to get married. They formed corporations throughout the Low Lands and into France and Germany that were self sustaining and largely independent of local control. These were huge organizations of women, working for themselves, under their own roofs and by their own rules. They produced crafts and textiles, they schooled nurses and they ran hospitals. Because they existed on the fringes of Church control, they were downplayed or even resented within the hierarchy. One result is that their achievements have largely been forgotten by history. When Mathias Hovius, the Archbishop of Mechelen, toured the facilities in 1601 he took the petty action of requiring Béguines who chose to keep lap-dogs to pay a fine to the Church. In 1630, Bishop Malderus of Antwerp defended the women in an extraordinary letter. He wrote,

The Order of the Béguines is truly not a religious order, but a pious society, and compared with the former complete consecration is as a preparatory school in which the piously inclined women of Belgium live after a pattern highly characteristic of the temper and mind and the character of the people. For this people is jealous of its liberty and will be led rather than driven. Although it is beyond a doubt more meritorious to devote one’s self to the service of heaven by vows of perpetual chastity, obedience, and poverty, and though there are many pious women in Belgium who are so disposed, yet most of them shrink from this irrevocable vow. They prefer to remain inviolably chaste rather than to promise to be so; they are willing to obey, but without formally binding themselves to obedience; to rather use their poverty in reasonable outlays for the poor than to give it at once up for good to all; rather voluntarily renounce daily the world than immure themselves once and forever.[2]

At the beginning of the seventeenth century, the hospital was used to treat wounded Spanish and Italian soldiers fighting in the war against the Dutch. By 1607, just before Antonio Neri wrote his letter, the staff at the hospital numbered fifty, “including seven doctors, eight surgeons, and three surgeon’s mates.”[3]

As the son of a grand duke’s personal physician and grandson of a surgeon, there can be little doubt that Neri had ample familiarity with medical procedure. It seems likely, given the circumstances, that in Mechelen he was lending his expertise to ease the ravages of war, helping to heal wounded soldiers.

[1] Lavinia L. Dock, Mary Adelaide Nutting, A History of Nursing (Putnam, 1907) v. 1, p. 268.
[2] Ibid, p. 269.[3] Geoffrey Parker, The Army of Flanders and the Spanish Road, 1567-1659 (Cambridge Univ. Press, 2004), p.141
[3] Ibid, Dock, Nutting 1907.
* This post first appeared here on 26 Mar 2014.