Zaffer

Basilique Cathédrale Notre-Dame de Chartres,

located 80 km (50 mi) southwest of Paris,

(constructed between 1194 and 1250).

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.

Primordial Matter

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 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.

Borgo Pinti

Palazzo Marzichi Lenzi, Florence

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 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 door 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.

Laughing in the Fern

Allain Manesson Mallet  1719,
"Der Mont. – Lune"

In Chapter 5 of L'Arte Vetraria, Antonio Neri shows how to extract salt for glass from fern plants in an evocative recipe. Fern was and still is widely abundant in Tuscany. It presented a ready source material for glassmakers of the region. Neri directs that harvesting of the plants be done in the spring:

Cut this herb from the ground when it is green, between the end of the month of May and mid June. The moon should be waxing and close to its opposition with the sun, because at this point the plant is in its perfection and gives a lot of salt, more than it would at other times and of better nature, strength and whiteness.

At first, it is tempting to dismiss this lunar influence as the product of a fertile imagination, but let us take a closer look. Even today, grandmothers throughout Italy remember the advice to pick vegetables from the garden and bring them into the kitchen at a half-moon. Can nona be completely off-track? The fact is that tidal forces of the moon do subtly affect plants, fish and animals in ways that can be measured. A closer look at Neri’s advice reveals reasoning that is hard to dismiss as mere astrological superstition. When the moon is waxing, tides rise and so do water tables. According to folklore, this is when sap rises from the roots of plants into stems and leaves. Sap carries the dissolved mineral salts required for glass. Neri also stipulates that harvesting should take place during lunar opposition. When the moon is 'opposed' to the sun, it is on the opposite side of the earth from the sun. In opposition, the moon is near full and rises as the sun sets. Plants see more light at night, leading to increased photosynthesis and growth.

In contrast, violin makers from Cremona valued high alpine spruce called moon wood. Trees were felled in the wintertime, when lunar tides were low. This minimized the amount of vibration deadening sap in the wood. In his Natural History, Pliny relates Cato’s advice on felling trees in accordance with the lunar cycle. In fact, centuries-old tradition specified lunar conditions for a host of needs from construction timbers to cheese boxes. In this case the advice relates to picking ferns for use in glass.

Fern ash is high in potassium carbonates. If carefully purified it can make an exceedingly clear glass, rivaling or even surpassing Venetian cristallo. It has the additional advantage of being physically tough, making it ideal for engraving or diamond-point work. On the other hand, once out of the furnace it stiffens quickly, giving it a short 'working life' for the hot glass artisan. This limits designs to simple basic forms. While soda-based glass was the norm for the Mediterranean region, throughout the Middle Ages and into the Renaissance, northern Europeans were more likely to be making potash-based glass. They utilized the potassium rich local trees and plants of the northern forests. In France, fern glass is called verre de fougère. In the considered opinion of some connoisseurs, wine tasted better when sipped from verre de fougère cups, hence the delightful expression 'le vin rit dans la fougère' [wine laughs (sparkles) in the fern].

Since the middle ages, fern glass became part of everyday life in northern Europe. It was familiar enough to find its way into literary verse on matters of the heart. There is a nice reference to fern glass by Geoffrey Chaucer, in The Squires Tale:

But notwithstanding, some said that it was

Wondrous to make fern-ashes into glass,

Since glass is nothing like the ash of fern;

But since long since of this thing men did learn,

Chaucer, in turn, borrowed this reference from an epic twenty-two thousand line French poem from the late thirteenth century, when the technique of making glass from ferns was already ancient.

* This post is a mashup of material that first appeared here on 5-7 August 2013.

Sonnet to 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 Antonio Neri's grandfather, and may 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.

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:

In all consideration, it is my proud duty to dedicate this book to none other than you, most Illustrious Excellency; for you have always been my outstanding patron. You are a gifted leader in this and in all other noble and worthy developments made continually in all the arts.

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 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 deal also gave him possession of the laboratory facility that his father had built and several other properties. That laboratory, 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 syphilis 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.

Carries the Palm

Entry into Jerusalem, 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 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.