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, April 28, 2017

Borgo Pinti (Part II)

Palazzo Ximenes Panciatichi da Sangallo,
68 Borgo Pinti, Florence.
Antonio Neri spent his childhood on Borgo Pinti in Florence. Although he would come to live and work in different parts of the city, then later in Pisa and Antwerp, it is here on this street that his impression of the world was first formed.

A short distance from the family house on Pinti was the Palazzo Ximenes, occupied by the wealthy Portuguese trader, Sebastiano Ximenes d'Aragona, with his cousin, Niccolò, and their families. The Ximenes ran a powerful trading empire with branches throughout Europe. Antonio Neri's future friend Emmanuel Ximenes was the brother of the above-mentioned Niccolò. Sebastiano was patriarch of the Florentine branch of the family, which had its origins in Castile. In 1593, Grand Duke Ferdinando I de' Medici made Sebastiano the Marquis of Saturnia. Both Emmanuel and Sebastiano were Christian knights of the order of Saint Stephen. However, the family traced its roots to Jewish ancestry in the Kingdom of Aragon, a region covering what is now northeastern Spain.

The same year that Christopher Columbus sailed for the new world, Jews in Spain and Portugal were forced to make the choice of embracing Christianity or forfeit their property and leave the country. Amid the lynch mobs that roamed the streets of Iberian cities, some families, the Ximenes among them, moved to more tolerant regions such as Tuscany and Flanders. Some Jews made a public embrace of Christianity, while in secret continuing to observe in the faith of their heritage. Others made a full conversion, joining confraternities like the Knights of Saint Stephen in an honest display of commitment. Membership in such groups was prestigious and helped stave criticism by those who might doubt them as true Christians. 

The Ximenes' house on Pinti was earlier owned by the celebrated architect and sculptor Giuliano da Sangallo, who renovated the Cestello Church – attended by Neri's family – for the Cistercian monks between 1481 and 1526. Sangallo was also the favorite architect of Lorenzo de' Medici. Folklore tells that in the house opposite Sangallo's, on Borgo Pinti, lived the child who would be raised by the Medici and become Clement VII (pope from 1523 to his death in 1534). According to the story, in 1478, after the assassination of Giuliano de' Medici, surviving brother Lorenzo was informed by Sangallo that Giuliano had an illegitimate son by the young woman living across the street. Lorenzo adopted the boy, who was named Giulio. Later, he became a close confidant to Lorenzo's son, Giovanni, later Leo X (pope 1513-1521), the first of four Medici popes. 

At the very end of the road on the left, just before the massive Pinti gate, was the residence of the city's archbishop, Alessandro Ottaviano de' Medici, the future Leo XI (pope from 1 to 27 April 1605). This property would become the grandest on the street, a sprawling formal garden overlooked by a massive palazzo, which is now called the Palazzo della Gherardesca. The estate was originally designed by neighbor Giuliano da Sangallo (for Bartolomeo della Scala) around 1480. The Archbishop bought and enlarged the property in 1585, annexing adjacent land purchased from the wool workers guild. 

Appointed archbishop in 1573, Alessandro Ottaviano de' Medici was the direct successor to Alessandro Altoviti, the godfather of Antonio Neri's older brother Jacopo. As court physician, there is every reason to believe that Antonio's father, royal physician Neri Neri, was well acquainted with his neighbor, the new archbishop; both men were part of the Medici inner circle. In 1583, Alessandro was made Cardinal. Had Neri Neri managed to live a few years longer, he would have seen his neighbor elected Pope in April of 1605. It was unfortunate for Alessandro that he did not have the doctor at his coronation to advise him against spending the entire day in the cold rain. The Holy Father fell ill and within the month, the last of the Medici Popes would be dead.

*This post first appeared here on 5 March 2014.

Wednesday, April 26, 2017

Borgo Pinti

Palazzo Marzichi Lenzi, Florence
Former home to famed glassmaker 
Antonio Neri
Located at 27 Borgo Pinti in Florence, the Neri house still stands today. It is now known as the Palazzo Marzichi-Lenzi, named after later owners. Pinti is an unassuming street on the east side of the city. It stretches northeast in nearly a straight line, anchored in Neri's time on either end by city gates. One gate leading out to the Tuscan hills, the other into a more ancient part of the city.

Looking northeast toward the hills of Fiesole, the far end of the street was marked by the imposing gate in the city's final fortress walls, completed in 1333 (now Piazale Donatello). It was the last of six progressive enlargements of the city since the early Roman Empire. Even long after this expansion of the city limits, the land around Pinti remained thinly populated, dotted with fruit trees and grazing fields. What started as a center for the wool industry in Florence, progressed into a haven for artists and sculptors, new construction boomed, and finally, around the time of Antonio's birth the area became a fashionable district for wealthy courtiers.

At the head of Borgo Pinti stood one of the oldest hospitals in Florence, San Paolo a Pinti,  documented as far back as the eleventh century. By the close of the sixteenth century, the small neighborhood hospital had been largely rendered superfluous by the much larger Santa Maria Nuova. Only a couple of blocks from San Paolo a Pinti, S. M.Nuova is where Antonio’s father Neri Neri would practice medicine. However, San Paolo was still apparently operating as a refuge where poor or infirmed travelers could find medicine and a bed for a couple of nights. The nearest apothecary was that of Luca Mini, located on the Piazza San Pier Maggiore, within easy range of both the hospital and of the Neri residence.

The Neri palazzo at no. 27 was erected in the fifteenth century, converted from what was a convent or a meditation house, which was in turn built upon much older structures dating from the 1300s. These were probably part of the Palazzo Ferrantini complex. The main house is now called the Palazzo Caccini and stands a few doors further, at no. 33 Borgo Pinti. In 1439, it hosted the Emperor of Constantinople John VIII Palaiologos, Patriarch Joseph II and his delegation, while attending the Ecumenical Council held in Florence. The Council began eight years earlier in Basil with the intent to address numerous issues, including unification between the Roman and several Eastern Orthodox Catholic churches. After nearly a decade of meetings, moving from one city to the next to accommodate politics and avoid the plague, they finally reached an accord in Florence, signed by the Patriarch, the Emperor and the Pope. However, two days later the elderly Joseph II died, and the agreement languished, never ratified by his fellow orthodox bishops back in Constantinople.  The hosts of the Emperor and Patriarch were the Ferrantini family, wealthy bankers in Florence since the thirteenth century.

Directly across the street was the residence and workshop of sculptor Giambologna, complete with a bronze foundry. Giambologna was a favorite of the Medici, and after a successful period working in a space set up in the Palazzo Vecchio courtyard. The newly crowned Grand Duke Ferdinando I de' Medici ordered the studio to be built on Borgo Pinti adjacent to the house that the artist had bought.  This was in the winter of 1587-88, just after the deaths of Francesco I and Bianca Capello, when Antonio turned twelve years old. Apparently, the studio, along with a grant of some land in the countryside was recompense for work done for Francesco I.  Giambologna specialized in large complex sculptures, and had a reputation for producing work with impeccable detail and smooth finished surfaces.

In the early 1500s Michelangelo Buonarroti, known to his countrymen as 'Il Divino' [the divine one], maintained a house with a spacious workshop somewhere on Borgo Pinti, it was paid for by the city cathedral, Santa Maria del Fiore, in anticipation of his sculpting the twelve apostles, a commission that was never fulfilled; only St. Matthew was started.  Shortly thereafter Pope Julius II called Michelangelo to work in Rome. In 1508 the sculptor would find himself flat on his back in the Sistine Chapel, holding a paintbrush instead of a chisel. Pinti land-owners Alamanno Salviati and Giuliano da Sangallo together recommended Michelangelo to Julius II.

For Antonio Neri, knowing an army once marched down his street led by the Pope's envoy, residing across the street from sculptor Giambologna, living on property that the Byzantine Emperor occupied for a couple of years; it all sounds spectacular, and it is spectacular. However, we must acknowledge that in the grand scheme of Florence, Antonio Neri's Borgo Pinti is a relatively minor attraction. One can confidently point to any address in Florence and be certain that something of historical significance – potentially of great significance – transpired there. Simply walking the streets, one is ensured of following in the footsteps of great artists, kings, queens, emperors and popes, but also of alchemists, glassmakers, and innumerable other souls whose stories are no less potent.

Monday, April 24, 2017

Cross Pollination

Throughout the Renaissance, Florence Italy was famous for its artistic output. Names like Donatello, Michelangelo and Giambologna graced the tongues of patrons across Europe. But the secret to the city’s fantastic creativity did not rest solely on individual superstars. The ruling Medici family had found a way to harness the talents of myriad lesser known artisans and use the fruits of their creative labor as a powerful political tool. 

Starting in the late sixteenth century, at Christmas time, boatloads of fine glass, ceramics, jewelry, stonework, and art sailed out from Tuscan ports as gifts to the royal families of Europe, who accepted the offerings gratefully. The Vatican, the Holy Roman Empire, Spain and France all had ambitions, at one time or another, to make Florence their own. These gifts, time and again, helped to smooth ruffled diplomatic feathers, reassure old allies and allowed tiny Tuscany to play the mighty kingdoms against each other, keeping Florence relatively unmolested. What the Florentines lacked in military might, they made up for in sheer artistic creativity.

At home, this strategy depended on the constant attraction of new talent and deep support of all the arts. At the Uffizi palace, Grand Duke Ferdinando set up  a kind of innovation center, called the Galleria dei Lavori (Gallery of the Works), where new techniques were pioneered. His father, Grand Duke Cosimo had already built a glass furnace there, staffed by Venetian masters imported from Murano. In adjacent areas, stone cutters worked minerals collected from around the world into fabulous inlaid table tops and floors in an art called pietre dure. Goldsmiths worked with gem cutters to create exquisite jewelry. Designers and illustrators brought the natural world into new creations that integrated these arts together for the first time. 

This was the world in which a young Antonio Neri grew up; the son of a famous physician, he matured into an alchemist with a profound respect for the healing arts, but also into a glassmaker—a conciatore—to the Medici prince Don Antonio. A key to Florence's creative output was the Medici innovation of housing artists of different disciplines under one roof. A cross pollination of ideas took place that spurred new ideas in individual arts, but also gave birth to the creation of objects which combined the talents of several different arts. Fine wooden furniture graced with inlaid stone, glass used to imitate exotic minerals and rock crystal, fanciful goblets and pitchers that integrated metalwork, glass, shell and other exotic materials.

This culture of cross pollination can be seen throughout Antonio Neri's work, in the variety of different glass recipes and also in his knowledge of the ways his glass was to be used. In his 1612 book, L'Arte Vetraria, he says:
Because in order to make vessels and drinking glasses where the glass is thin, you must really load it with a lot of color, but for making large cane for beads not so great a charge of color is necessary. For making thin cane for small beads, you must charge it well with color. In working the glass, you must apportion it with more or less color according to the purpose it must serve.
For lead crystal artisans, he has this advice:
To work lead glass into various drinking glasses or other vessels, or even to draw cane for beadmaking, it is necessary to raise the punty [out of the melt], and to make a gather of glass by turning. Take it out, let it cool somewhat and then work it on a well-cleaned marble [marver]. The marble should be somewhat cool, and well bathed with water before use.
This practice will ensure that the paste of the lead glass does not pull up any of the marble. The glass will always gall marble not bathed in water. Some chips will incorporate into the work, giving it an ugly look. Therefore, frequently flush the marble with fresh water for as long as you are working the glass. Otherwise, all its grace and beauty will be lost.


Unlike his famous brethren Donatello, Michelangelo and his neighbor Giambologna, Antonio Neri was not a superstar and as an alchemist he did not work alone; he was part of a team. He ably represents the small army of workers who supported the Medici creative machine that spread fine craftwork throughout Europe. 

*This post first appeared here on 19 March 2014.

Friday, April 21, 2017

Zaffer

Antique Apothecary jars,
cobalt blue glass.
As best as I can remember, the first time that I really noticed glass was at four or five years old, at my grandmother's house in Queens, New York. The sunlight filtering through a low window caught my eye with a brilliant blue glint through a small cobalt glass bottle.  My grandmother held it up to the light for me and I was enchanted; transported into a realm of exquisite pure color.

Little did I know that the spell cast on me at such a young age had been cast on Egyptian pharaohs of the eighteenth dynasty and on Persian princesses, two thousands years ago, by their cobalt glass jewelry. In all three cases, the deep rich blue of cobalt oxide glass was responsible. Today, the source of ancient Middle Eastern cobalt is unknown, possibly West Africa, but more recently, in the Renaissance; it was mined in Hungary, in Bohemia and in German Saxony, where it was called "zaffer," after its sapphire color.

Legend tells that sixteenth century silver miners in Germany amassed a hoard of smaltite thinking it was silver ore. When they tried to smelt it, the arsenic which cobalt ores always have, evolved highly toxic fumes that made them sick. Discouraged and maligned, they said the product of their labors was cursed by goblins; they named it "kobald" (cobalt) after the evil spirits. The theme of 'evil spirits' (toxic fumes) was common in mining circles. A mythology persisted from ancient times up until the eighteenth century that divided the spirits into two groups; mischievous, and malevolent. The mischievous spirits played tricks on the miner's perception and equipment, the malevolent spirits could stop a man dead in his tracks, literally. 

Regardless of the difficulties both terestrial and otherwise, a strong market developed for the newly found "kobald" among artists for paint, potters for glazes, and glassmakers. The Saxon miners gained a reputation for producing the finest zaffer.

In his glassmaking book L'Arte Vetraria, Antonio Neri describes his method for purifying and preparing zaffer for use in glass. It is a recipe that would stand the test of time, still quoted by authors into the nineteenth and twentieth century.

To Prepare Zaffer, Which Serves for Many Colors in the Art of Glassmaking

You should get zaffer in large pieces and put it in earthenware oven-pans holding it in the furnace chamber for half a day. Then put it into iron ladles to inflame it in the furnace. Heat it well, then take and sprinkle it with strong vinegar. When cold, grind it finely over a porphyry stone into glazed earthen pots with hot water. Then wash more water over it always leaving the zaffer to settle in the bottom.

Now gently decant, to carry away the sediment and impurities of the zaffer. The good part and pigment of the zaffer will remain in the bottom. The pigment remains are now prepared and purified to be far better than it was at first, which will make clear and limpid pigment. This zaffer should be dried and kept in sealed vessels for use, which will be much improved over the original.


Until the mid 1700s zaffer had been associated with silver and copper mines, and was commonly thought to be a derivative of copper. It was Swedish chemist Georg Brandt who finally isolated the new metal, and gave it the name which honors the miners and the subterranean spirits which still can cast a spell on us through its deep pure blue color in glass.

* This post first appeared here in a slightly different form on 4 April 2014.

Wednesday, April 19, 2017

Don Antonio de'Medici

Don Antonio de' Medici
Frontispiece from Pierfilippo Covoni 1892
In 1612, Priest Antonio Neri published his book of glassmaking recipes. L'Arte Vetraria went on to become a primary reference for glass artisans throughout Europe. He dedicated his book to Prince Don Antonio de' Medici the son of Grand Duke Francesco I:
I have considered dedicating this book to none other than you, most Illustrious Excellency; for you have always been my outstanding patron and you understand this and all other worthy and precious knowledge. In fact, you always practice all the arts requested of a true and generous Prince. I implore you therefore to accept if not my work, then my complete devotion to your great merit and virtue, Excellency. I pray that God will fill you with happiness.
As an eleven year-old, Don Antonio was slated to succeed his father as the next Grand Duke of Tuscany, but that situation changed quickly. In the autumn of 1587 the young prince lost both of his parents in the space of a few days. They both fell extremely ill and died within a short time of each other. Rumors flew that Francesco de' Neri and Bianca Capello had been poisoned, but forensic investigators have since found pernicious malaria pathogens in Francesco’s remains, a disease with symptoms consistent with the reports of physicians on the scene. Historians trace their infection to an outing in the damp forest a few days earlier, where they had probably been bitten by mosquitoes carrying the disease. 

The boy’s uncle, Cardinal Ferdinando took charge, consolidated power and excluded Don Antonio from the royal succession, although he was given a prominent place at court as a diplomat. As part of a deal that he would never marry, he was allowed to keep the title of Prince of Capestrano, to which was added Grand Prior of Pisa, in the Knights of Malta. The agreement also gave him possession of the laboratory facility that his father had built s well as several other properties. That laboratory on the north side of Florence, the Casino di San Marco would become the prince’s residence and the place where Antonio Neri would learn about glass formulation.

Poor health attended Don Antonio from his first months through the end of his life. Doctors and medical examinations were to become a regular part of his routine; they may well have inspired his later pursuit of medicinal cures, as well as his foray into alchemy, which also involved Antonio Neri. At some point, probably as a teenager, Don Antonio contracted syphilis, a condition that may well have been treated by Antonio Neri’s father who was physician to the royal family.

The prince had played a major part in Neri's life, elevating him into the upper stratum of Florentine craftsmen and to the forefront of alchemical research in Europe. However, in another manuscript, Discorso, we see a different side of Neri. On the subject of turning base metals into gold, the priest was less forthcoming:
I would add that God's providence over human affairs must not easily allow many to acquire this art, particularly not the great princes. It should not be made clear and common to the vulgar, because in this way, gold and silver and consequently coins lose their value, so that the good order of human trade will be disrupted and we should go back to the ancient barter of things that are necessary to a civil life, creating great disruption and confusion.
Although never allowed to marry, over his lifetime Don Antonio managed to have a number of children; his last three sons were ultimately legitimized by the pope as Medici heirs. In the end, it was the slow, progressive ravages of his disease that brought him down. He died in 1621, at the age of forty-five, unable to leave his bed. He was given a proper funeral, and interred at the Medici chapel of princes in Florence.

*this post first appeared here on 12 May 2014.

Monday, April 17, 2017

Archiater

Antonio Neri's family arms, from the vestibule
of the Palazzo Marzichi-Lenzi, Florence.
Archiater was a title used in ancient times for the doctors of Roman Emperors. Later, this term was applied to the head physicians of rulers throughout Europe. Even today, the pope’s chief physician holds the official title of archiater. 

In 1612 Florence, Antonio Neri wrote the first book devoted to glass formulation. His benefactor was Don Antonio de’ Medici, an alchemist prince from the royal family. There is no doubt that Antonio Neri gained some of his expertise at the prince’s laboratory, but his start in the chemical arts is probably owed to his own father. In the late sixteenth century, his father Neri Neri was appointed to the position of personal physician to the grand duke of Tuscany, Ferdinando I. For Antonio’s childhood and teenage years his father was the most esteemed doctor in all of Tuscany. 

Today, the connection between medicine, alchemy and glassmaking might not be so obvious, but in the early seventeenth century all three professions required use of similar materials, equipment and techniques. In the late 1580s, approaching the age of fifty, Antonio Neri's father was appointed the personal physician to Grand Duke Ferdinando de' Medici. The son of a barber-surgeon, Neri di Jacopo Neri - or Neri Neri, as he was known - had parlayed a degree in medicine into a successful and prosperous career. His elevation to 'citizen' status, a decade earlier, gave him entree into the world of the patrician elite and his appointment as royal physician secured a place for his young family near the top of the Florentine social hierarchy.

The fact that Neri Neri gained citizenship at the age of forty and did so together with his father shows it was not a legacy, but perhaps their medical prowess that lead to the award. One requirement of citizenship was possession of a domicile within the city. The baptism register lists Antonio and all of his siblings as residents of San Pier Maggiore parish, long before the citizenship grant. However, it is in the 1580s that we see the first reference to Neri Neri's ownership of the palazzo at what is now 27 Borgo Pinti.

Baccio Valori was librarian, keeper of the royal herbal gardens and the godfather of Antonio Neri's older sister Lessandra. In 1587, Valori received a letter from Filippo Sassetti, sent from India. Filippo was a native Florentine, the nephew of Antonio Neri's godmother, Ginevra Sassetti. He attended university in Pisa with Valori and they became lifelong friends. In the letter, he notes that he has collected rare varieties of cinnamon in his travels along the Malibar coast. His intention was to rediscover the species thought to be a powerful cure of disease by the ancients. He planned to send a parcel of seeds of these and other medicinal plants. "If it pleases God, in the coming year, I will send this to you, so that you may see it all, together with our Messer Neri Neri, who graces my memories."

In the autumn of 1587, Grand Duke Francesco I de' Medici and his wife Bianca Cappello both became ill and died during a visit by the grand duke's younger brother Cardinal Ferdinando. Pernicious malaria was to blame and accounts by physicians on the scene described identical symptoms for husband and wife. The thirty-eight-year-old Cardinal Ferdinando relocated to Florence from Rome; he took charge and assumed power as the new grand duke of Tuscany. Shortly after, he appointed Neri Neri as his head physician.


*This post first appeared here on 14 August 2013.

Friday, April 14, 2017

Primordial Matter

16th century Mining practices, 
from Agricola, De Re Metallica
In the early seventeenth century, Florentine priest Antonio Neri wrote the first printed book devoted to formulating glass from raw materials. His work is called L'Arte Vetraria, which translates to "the art of glassmaking." The book became quite famous and this is what he is remembered for today, yet he considered himself first and foremost an alchemist. In previous posts, we have explored the commonalities between glassmaking, medicine and the apothecary's trade. Another field closely connected to alchemy was mining. 

In the seventeenth century, the earth was considered a living entity; metals were found to occur in "veins" which were thought to grow and once mined, regenerate over time. The metals themselves were thought to undergo a maturation process. Primordial material left over from the creation of the world exerted its influence deep in the ground. Nurtured by the earth, under the influence of the suns rays, a process took place that eventually turned base metals into the more noble silver and gold. As far as Neri was concerned, alchemy was the art of imitating and enhancing natural processes that were already at work. In his manuscript Discorso, he writes:
I feel that the more perfect the art the most simple it is; so the authors [of alchemy] most unanimously agree that the ‘primordial material’ [prima materia] of the [philosopher’s] stone is something vile [base] and not bought with money, but easy to find. Moreover, the manner of work must imitate nature, which in order to produce gold makes use of the singular or simple material, which is the seed of gold, of a single vessel, which is the ‘womb of the earth’ [seno della terra] and of a single natural and vital fire, which is the sun.*
Elsewhere in the manuscript, Neri discusses several specific mines. He discusses the use of "vitriol" water that flowed in certain mines and how it could be used to transmute iron into copper. He discusses an unidentified mine "some distance from Leiden" and another in Slovakia in the town of Smolnik. It is reasonable to think that Neri visited these places himself. A third location, which he purposely keeps under wraps, is where he obtained "immature" gold that he was able to "multiply" through alchemical manipulation. With a certain disappointment, he writes "To this day I have never found another mine like it, and therefore suitable for this purpose." Clearly, he spent a significant portion of his time looking. He advises:
The gold mines are not all in the same condition, which is well understood for those of silver and all the other [metals]. Some are already perfect, in which nature has done what it could do and reduced the gold to its maturity, while other [mines] are still imperfect and in their infancy*
In his work for Medici prince Don Antonio in Florence, Neri's assistant/disciple was Agnolo della Casa. Della Casa took copious notes of Neri's experiments, and literally filled thousands of pages in notebooks that are today held by the National Library in Florence. Much of this material dealt with the transmutation of metals, and as we have seen Neri was not only concerned with materials, but with their specific place of origin. His first manuscript was titled "Treasure of the World, By Priest Antonio Neri – which [covers] the whole of alchemy with various illustrations, not only of the furnaces, vessels and chemical instruments but with other illustrations concerning the mining of all the metals." For he and his colleagues, mining and alchemy shared theoretical connections but also familial ones. Della Casa had a relative named Filippo Talducci della Casa (1543- c.1615), who was a celebrated alchemist and mining engineer, working in Prague and Krakow for the Holy Roman Emperor. Last but not least, there was also a practical connection. Mining provided many of the raw materials used in Antonio Neri’s glassmaking activities.  

* For a full discussion of Neri’s Discorso, see M. G. Grazzini, “Discorso sopra la Chimica: The Paracelsian Philosophy of Antonio Neri”, Nuncius 27, pp. 411-467.

** This post first appeared here 30 April 2014.

Wednesday, April 12, 2017

Carries The Palm

Jesus' entry into Jerusalem, walking on palm leaves.
 Pietro Lorenzetti 1320
For Western Christians, this week began with "Palm Sunday," a feast day that falls on the Sunday before Easter and celebrates Jesus' entry into Jerusalem. His procession is said to have included his followers laying palm tree leaves before him along his path. The connection to seventeenth century priest and glassmaker Antonio Neri is this: In his book L'Arte Vetraria, Neri describes his very best green glass with a colloquial expression; saying the recipe "carries the palm" for all other greens.   


Saint Justina of Padua with a palm frond,
Bartolo Montagna 1490s
In his book, Neri presents a string of recipes for variations of green glass. Finally, in chapter 35, he presents his ultimate green, which he titles: "Another Green, Which 'Carries the Palm' for All Other Greens, Invented by Me." The phrase "carries the palm" alludes to the biblical story of Jesus entering Jerusalem, in which the people welcomed him by laying down cloth and palm branches on the ground in his path. Even before that, the palm branch served as a symbol of victory; in ancient Greece, palm fronds were awarded to victorious athletes. Later in history, Roman lawyers who won a case decorated their doors with palm leaves.


Copper Sulfate (vitriol of copper)
Cristallino was a mid-grade glass made with a soda based plant ash from the Levant which Neri called "rocchetta." For this recipe, he blends it with common glass, and adds red lead oxide to the mix, in effect forming an early version of what we now call lead crystal. He "cleans" the glass by using the well-established technique of flinging the molten glass into a large tub of clean water. This had the effect of "washing out" excess glass salt (flux). In addition, it provided the opportunity to sort through the fragments to remove any undissolved metallic lead. Lead that did not go into the glass had the tendency to collect at the bottom of the clay crucible as lumps of molten metal. It could then eat a hole in the vessel, resulting in a glass-shop disaster, as Neri warns: 
All lead precipitating out of the glass must be removed with diligence, throwing it away, so that it does not make the bottom of the crucible break out, as can happen. Return the glass that was thrown in water to the crucible and leave it to clarify for a day. Then add the color using the powder, made chemically by the dry distillation of vitriol of copper [chapter 31]. Also, add a little crocus of iron, but very little. The result will be a most marvelous beautiful green, the best that I ever made. It will seem just like an emerald of ancient oriental rock, and you can use it in every sort of job.
The "crocus of iron" mentioned above is simply iron oxide or 'rust' as it is more commonly known. The "vitriol of copper" he refers to is copper sulfate. Neri forms it in a laborious process that involves cutting copper sheet into small, coin-sized pieces, mixing it with sulfur, heating in the furnace and then reprocessing it several times. The result is then added to water and the soluble part is further processed, filtered and evaporated. The final product is a pure blue crystalline material that has uses for our alchemist that go far beyond glassmaking, as he alludes to in the final sentence of the book:
Although I have placed here the way to make this powder with much clarity, do not presuppose that I have described a way to make something ordinary, but rather a true treasure of nature, and this for the delight of kind and curious spirits.
*This post first appeared her in a slightly different form on 25 October 2013.

Monday, April 10, 2017

Washing Molten Glass

Washing, sorting and carrying cullet
Denis Diderot 1772
One of the continuing frustrations with the study of glassmaker Antonio Neri, is that there is no known example of his glass to be found anywhere. It is very possible that pieces do survive, but so far, none has been tied to him or his recipes. At first it might seem to be a straightforward task of analyzing the composition of likely candidates and comparing the results to his formulas. Unfortunately, this plan does not hold water. Even if a recipe for glass was followed exactly, the result will have a different composition from the starting materials. One reason is that before the hot glass was crafted by artisans, a new batch was typically "washed" by flinging ladlefuls of molten glass into great vats of cold, clean water. In his 1612 book L'Arte Vetraria Neri wrote:
After a while, when the glass is well fused, take it out of the crucibles and throw it into large earthenware pans or clean sturdy wooden tubs filled with fresh water. This step of throwing the glass into water has the effect of causing the water to remove a kind of salt called Alkali salt [glass gall], which ruins the cristallo and makes it dark and cloudy. So while it is still being worked let the glass spit out this salt, a substance quite foul, then return it to clean crucibles. Carry out this flinging into water repeatedly as necessary. In order to separate the cristallo from all its [alkali] salt, this should be repeated to the satisfaction of the furnace conciatore [glassmaker].
This step, he assures us, is absolutely necessary for the finest glass, but also helps improve the most common glass:
If you throw it into water at least one time, what you will have will be beautiful and clear. The same is true for common glass, which once brought to perfection you should return to the crucibles for use. It will be bright, fine and quite satisfactory to work in those jobs that require it. […] when a more than ordinary fine glass is desired it is necessary. Beyond becoming very white[clear], it calcines and clarifies nicely with few impurities.
This technique becomes even more critical for Neri's lead crystal, in fact, any glassmaker who ignored this step for a leaded glass did so at risk of a major disaster.
In a few hours everything will have clarified, now purify it by throwing it in water. Inspect the glass carefully before returning it to the crucible. All lead precipitating out of the glass must be removed with diligence, throwing it away, so that it does not make the bottom of the crucible break out, as can happen. Return the glass that was thrown in water to the crucible and leave it to clarify for a day.
In addition to washing the glass, sometimes the top layer of a melt was skimmed off and discarded because it contained contaminants that floated to the surface. To complicate matters further, molten glass can stratify in the crucible, meaning the composition might vary from top to bottom and from the center of the pot to the edges. 

Scientists and historians have collaborated to see what can be learned from period samples of glass. When attention is focused on the composition of a single type of glass, like Venetian style cristallo for example, one might expect a wide variation. The opposite turns out to be true. Even with all of these factors conspiring to change the glass composition, remarkably the analysis shows it is quite difficult to tell apart glass that was known to be made in Florence from that of Antwerp or Venice. Recent efforts have centered on identifying minuscule amounts of trace materials in the old glass that were unique to the raw ingredients of a specific region. Meanwhile, Antonio Neri's glass continues to elude us, even though it might be sitting on the shelves of museums around the world, right in front of our eyes.

* This post first appeared here on 9 May 2014.

Friday, April 7, 2017

The Glassmaker's Salamander

From Michael Maier's 1617 book of emblems.
The salamander was thought to be born of fire.
If one can say that hot-glass workers have a mascot, it is without any doubt the salamander. Since ancient times, this lizard-like, poisonous skinned amphibian was ascribed to exist within fire, even to be born out of the flames. According to legend, its cold body allowed it to survive the heat. To see one in the flames of a furnace was considered good luck, but glassblowers who suddenly disappeared (to work elsewhere) were said to have been "eaten by the salamander." 

Glass work has always been a hot, sweaty, exhausting affair. It is not surprising that after a long day's labor one might honestly think they saw small animals scampering around in the fire. The legend, however, is an ancient one; Aristotle, in his History of Animals reported that salamanders were thought to possess the ability to put out fire with their bodies. They became part of the lore among glassmakers in Venice on Murano and were even spotted in Antonio Neri's Florence. In his autobiography (1558-1567), Florentine artist Benvenuto Cellini offers this recollection:
When I was about five years old my father happened to be in a basement-chamber of our house, where they had been washing, and where a good fire of oak-logs was still burning; he had a viol in his hand, and was playing and singing alone beside the fire. The weather was very cold. Happening to look into the fire, he spied in the middle of those most burning flames a little creature like a lizard, which was sporting in the core of the intensest coals. Becoming instantly aware of what the thing was, he had my sister and me called, and pointing it out to us children, gave me a great box on the ears, which caused me to howl and weep with all my might. Then he pacified me good-humouredly, and spoke as follows: 'My dear little boy, I am not striking you for any wrong that you have done, but only to make you remember that that lizard which you see in the fire is a salamander, a creature which has never been seen before by anyone of whom we have credible information.' So saying he kissed me and gave me some pieces of money.

Incidentally, at the end of Cellini's life, family friend and Church canon  Piero della Stufa was appointed to settle his estate. Among other items, he was entrusted with the manuscript for Cellini's autobiography, from which the above quote is taken. Della Stufa was also the godfather to Antonio Neri's younger brother Vincenzio.
  
(Quotation from: J. Addington Symonds "Benvenuto Cellini's Autobiography" in Harvard Classics v. 31, Charles W. Elliot, ed. (New York: P. F. Collier & Son, 1910), p. 11 (book I, ch. V.))
* This post first appeared here, in a somewhat different form on 19 August 2013.

Wednesday, April 5, 2017

Rosichiero Glass

Sunset over Venice
(click to enlarge)
The most famous glass recipe in Antonio Neri’s 1612 book, L'Arte Vetraria, is “#129 Transparent Red.” The reason for its notoriety is, of course, the pure gold used as a pigment. Gold-ruby, or “rubino” is a devilishly difficult color to produce in glass and was not reliably duplicated until many years after Neri’s death, although pieces made in ancient times have been unearthed.  

Even though gold rubino is Neri's most well known recipe and certainly his most famous red glass, this recipe does not exist in isolation. In fact, it fits in the middle of a group of eleven recipes (120–130) devoted to transparent, or at least translucent red glass, enamel and related preparations. 


120 Transparent Red in Glass.
121 Red Like Blood.
122 Balas Color.
123 To extract the Spirit of Saturn, Which Serves Many Uses in Enamels and Glasses.
124 Rosichiero to Enamel Gold.
125 Rosichiero for Gold by Another Method.
126 How to Fix Sulfur for the Above Described Work.
127 A Glass as Red as Blood, Which Can Serve as Rosichiero.
128 A Proven Way to Make Rosichiero.
129 Transparent Red.
130 The Way to Fix Sulfur for Rosichiero to Enamel Gold.


A particular shade that was popular at the time was known in Italian as "rosichiero." Our glassmaker presents four different recipes and two more on “fixing” sulfur, which some of the preparations require. Most dictionaries cite Neri as the first to use of the word 'rosichiero' in print, but we know it was a common term of art among glassmakers much earlier. The French equivalent is "rouge clair." The Spanish edition of L'Arte Vetraria notes that in that language the term is “rosicler,” which is still used today to describe the intense rosy twilight color of a nice sunset.

The red glasses of this group all call for the addition of copper as a colorant and copper has remained a popular pigment up to the present. For instance, red traffic lights that are made of glass are typically tinted with copper. But that is not the entire story; some of Neri's rosichieros also include the addition of sulfur and some require hematite or iron oxide, red lead oxide, manganese oxide, or wine tartar. In his recipe #125 for rosichiero, he starts with four pounds of high quality cristallo glass. To this adds equal parts of tin and lead oxides, mixed together: 
[A]dd this calx little by little, ½ oz at a time, let it incorporate, and watch for when the glass becomes an ash gray color, at which point it will be good. Do not add too much calx because if you overload it, the glass will become white in color, which is not good.When it turns the said gray color, do not add more calx but leave it to clarify. Then have 2 oz fine minium [red lead oxide], add this to the glass, and let it incorporate well, and clarify. When it clarifies well, throw into water, return it to the crucible and leave it for 8 hours [in the furnace]. 

Have ½ oz of calcined copper, that is to say red copper and ½ oz of raw white [wine] tartar. Throw these materials in, and stir them well. Now add a dram of hematite, which the sword makers use for burnishing, and 1 dram of fixed sulfur. Stir and incorporate these powders, and watch. If it is over-colored, give it a little manganese to dilute it. If it is clear of color, add more of the fixed sulfur, hematite, a little red copper and a little white wine tartar at your discretion so it becomes the desired color.
None of these ingredients excepting copper is common in color glass production today; in fact, sulfur is usually considered an undesirable contaminant. Hematite is a naturally occurring mineral form of iron oxide. It is so named because if abraded in water it tints the water red, appearing to bleed. Hematite is not currently used as a red pigment in glass, but it is commonly used in some pottery glazes. 

From a chemistry standpoint, a good guess is that sulfur added to the glass would react with the copper and iron to produce various sulfide compounds. How those compounds affect the color and texture of the glass is an open question. Here is where we get into uncharted territory; four hundred years after Neri’s book was first published, predicting colors based on chemistry is no easier for us than it was for him. The science of color in general remains a difficult nut to crack. However, the fact that there is still much that we do not understand does not prevent us from enjoying the brilliant reds inspired by a good sunset.

* For the technically minded, the University of Oslo has a wonderful presentation on the state of color physics. For the non-technical, take a look – a series of fascinating images that spans the sense of sight and beyond. There is a link address in the "picture credits" for this post.

** This post first appeared here on 24 April 2014.

Monday, April 3, 2017

Sonnet for a Barber

Possible portrait of Lodovico Domenichi,
British Museum, inventory #1867,1012.650
In honor of National Poetry Month in the US, here is a post about a 16th century poet who was best friends with alchemist/glassmaker Antonio Neri's grandfather, and may even be the inspiration for the glassmaker's middle name: Lodovico. Neri, born in 1576,  is remembered mostly for his book of glass recipes, L'Arte Vetraria, yet he considered himself first and foremost an alchemist. His father was the personal physician to the grand duke of Tuscany, and his grandfather was a barber surgeon, who probably lived in the family house until his death in 1594, when Antonio was an 18-year-old. There can be little question that our glassmaker/alchemist was steeped in chemistry and medicine from a very early age, but perhaps also literature. 

In November of 1554, poet Lodovico Domenichi wrote a sonnet to his friend, Jacopo Neri. Jacopo was from Dicomano in the upper Arno River valley, then living in Florence with his young family. Domenichi was serving a sentence of house arrest in a wretched paper mill in Pescia, in the hills north of Florence. He had been found guilty by the inquisition on charges of translating the heretical writing of John Calvin into vernacular Italian, a crime for which the poet could have easily been executed. Luckily, he had friends in high places and after some nervous time spent in the stockade in Pisa, his sentence was reduced and later commuted by Grand Duke Cosimo I de' Medici.

Jacopo Neri had taken ill with a grave infirmity and when word reached Domenichi, he took pen to paper and composed seventy stanzas in the style of Petrarch. In so doing he bestowed a precious gift, the only one he could under the circumstances; he immortalized his good friend on paper. The sonnet starts:

      As I have now come to understand your
      Perilous illness and health,
      It is both grief and fondness that I show

      So may merciful God help you,
      Without delay, lest this vile world lose
      So much goodness in you, so much virtue.

In the sonnet, he goes on to extol Jacopo's kindness towards patients, his willingness to forgive and his admiration among scholars. Along the way, Domenichi describes his own predicament; the cruelties of the mill workers, the muddy floors, his desire to flee and trying to sleep on a bed of frozen straw among the work animals. The rain has been falling for weeks and he is miserable. Recalling happier times he evokes the memories of many mutual friends, including a dwarf named Don Gabriello Franceschi, who delivered sermons at the Cestello church, Neri's family church, located a few hundred feet from his front door. Franceschi was from the family into which Jacopo's daughter, Faustina, would later marry. 

      There he is called Don Gabriello 
      Franceschi and I am honored, for good reason,
      A giant of men in a small handsome package.

He goes on to describe his saviors; the men who intervened with the Church on his behalf. One was Pompeo della Barba, educated at Pisa and later called to Rome as the personal physician to Pope Pius IV. In the end, Domenichi was pardoned, allowed to leave the damp mill and return to Florence. Within a short time, he was appointed court historian to Cosimo I. Over his career, he published many volumes; translations of works ranging from Xenophon, to Plutarch, to Pliny's Natural History, to a groundbreaking compilation of poems by contemporary women. At the end of his life, Domenichi suffered devastating debilitation, maybe from a stroke, which robbed him of the ability to speak. Even so, he still received regular visits from his old friend Jacopo Neri the barber surgeon. As we turn away from the subject of Lodovico Domenichi, it is hard to resist speculating that a decade after his death, the poet was remembered with fondness by the Neri family in the christening of our glassmaker, whose full name is Antonio Lodovico Neri.

Lodovico Domenichi, "A Mastro Jacopo di Neri, Cerusico, E Barbiere." in Il Secondo libro dell' Opere Burlesche, di M. Francesco Berni.  (Fiorenza: Apresso li Heredi di Bernardo Giunti, 1555), vv. 2. Reprinted many times. 
*This post first appeared 9 September 2013.