Glass Pearls

 

Johannes Vermeer

"Girl with a pearl earring" (1665-6)

Natural pearls, found inside various seashells, have been prized and worn as jewelry since antiquity. The pearl is formed as a secretion of the mollusk; it is the animal's response to an irritant, perhaps a sharp grain of sand, which has become lodged in its tissue. The secretion, called "nacre" is the same material from which the mollusk builds and enlarges its shell. Natural pearls are rare; large, well formed ones are even more so. A famous legend claims that Cleopatra used pearls to win a bet with Marc Antony: that she could spend ten million sesterces on a single meal. She literally drank pearls that had been ground up and dissolved in wine. Because of the difficulty in obtaining pearls, and their high demand among the wealthy, it is not surprising that like artificial gems, artificial pearls have enjoyed a brisk trade throughout history.

In Antonio Neri's era, the early seventeenth century, a number of recipes used glue, egg whites or other organic materials to simulate pearls. These had the obvious disadvantage of being susceptible to degradation by moisture and physical handling. Another alternative was to simulate pearls with glass, and on this count, Neri does not disappoint. Recipe number sixty in his 1612 book L'Arte Vetraria gives his prescription for artificial pearls. Here it is in its entirety:

In fused and clarified cristallo, add three or four portions of tartar from wine dregs. You must thoroughly calcine this tartar to a white color. Stir it thoroughly into the glass, and continue to add more tartar, also well calcined until it is white. Add four to six more portions, always stirring the glass thoroughly, continuing thus until the cristallo takes on a pearl color. In this recipe, I cannot give exact rules, because it is a matter of experience, which is gained through experimentation. Once obtained, you must work the color quickly, because it will dissipate. I have practiced and experimented with this method many times.

"Cristallo" is the exceptionally clear glass the Venetians developed, perfected and were renowned for throughout Europe. "Tartar" is a crystalline growth that forms on the inside of wine casks, what we now know as "cream of tartar." Occasionally, one might spot crystals at the bottom of bottles of wine. They are a rich source of potassium. Neri, the Venetians and others had used tartar as a glass flux over a period of centuries. Here, however, he is not using it as a flux, but as a colorant to give the glass the pearl's shimmering appearance. His claim to making many batches of this glass implies large numbers of artificial pearls were in circulation. Our glassmaker presents a second recipe, which does not make any mention of pearls, but oddly may have much more to do with the evolution of reproducing these treasures of the sea. Recipe number 114 is entitled "The Way to Tint Glass Balls, and Others Vessels of Clear Glass, From the Inside, In All Kinds of Colors, So They Will Imitate Natural Stones." Here, Neri spreads fish-glue on the inside surface of a blown globe of clear glass, followed by various pigments.

Even in his time, artificial pearls found their way into royal courts and onto the canvasses of master painters. The fashion-setting monarchs of France and Britain Catherine de' Medici and Elizabeth I were famous for their extravagant love of pearls. Elizabeth famously purchased faux pearls from Venetian glassmakers to adorn her garments. She commissioned many portraits donning her pearl studded creations. Referring to the famous painting by Johannes Vermeer, Lloyd Schwartz recently observed, "[T]he scholarship on Girl with a Pearl Earring reveals that the pearl isn't really a pearl […] the famous pearl is probably just glass painted to look like a pearl."* It is interesting to note that Vermeer's famous painting was executed in 1665-6, within five years after three reprints of Neri’s book, two in Italian one in English, and only a couple of years before a Latin edition printed in Vermeer's own country.

Around 1680, a Parisian maker of rosary beads invented a type of artificial pearl consisting of a small hollow glass bead, painted on the inside with the iridescent discharge of fish scales mixed with glue. He then filled the beads with wax. Jacquin had apparently rediscovered the shimmering pearly residue of a specific fish. His innovation fueled a new industry; he called the precious pigment "essence d'orient." But the material had already been employed in eastern France in 1656 and according to other reports as early as the reign of Henry IV of France (1572–1610), which closely coincides with Antonio Neri's own lifetime. By 1716, scientists were investigating essence d'orient under a microscope. Rene Antoine Ferchault de Reaumur reported tiny, perfectly formed rectangular plates that reflect the light to cause the shimmering.**

Perhaps more interesting than who discovered what, is the exchange of ideas and the overlap of interest between an Italian alchemist, a British queen, a Dutch painter, a French jeweler and a biologist.


* Also see Anthony Bailey, A View of Delft: Vermeer Then and Now (London: Chatto & Windus, 2001), p. 123, 124.
** For an English summary see The Edinburgh Philosophical Journal October 1839-April 1840 (Edinburgh: Adam & Charles Black, 1840), v. 28, p. 114, 115.

Lead Crystal

 

Roemer type drinking glass c. 1677,

George Ravenscroft.

The entire fourth part of Antonio Neri's 1612 book L'Arte Vetraria is devoted to the preparation of lead glass, a forerunner of what is now commonly known as lead crystal. This section is unique in the book in that it contains the only instance of the author giving direct advice to glass artists themselves:

"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."

He goes on to describe what might be termed a kind of dance with the glass. As with a human partner, gentle patience is required in learning the boundaries of what can and cannot be done. Ultimately, an artist must come to understand the material's behavior and personality in order to result in a great partnership. For the artist who makes unrealistic demands, glass can be a heartbreaker.  

"This sort of glass, lead glass, is so runny that were it not cooled, and taken up by turning [the punty] to wind a gather, it would be impossible to work. It is so runny that it would not even hold onto the punty, because it is as loose as soup. This arises out of [the fact that] the lead calx causes it to become very fluid."

"Namely, gather the glass little by little, allow it to cool, and work it over marble frequently bathed in water. Furthermore, make sure to keep the pot of glass rather calm, and in a place in the furnace where it will not see too much heat, otherwise it will not be possible to work this glass at all."

The formulation of lead crystal as we know it is a relatively recent development. This is a composition of crushed silica (sand or quartz), potash (potassium carbonates) and lead oxide substituting for calcium to stabilize the composition. It is also true that lead has been added to glass since its invention a few thousand years ago. It is not clear that this addition was always intentional, but a Babylonian tablet of 1700 BCE gives a recipe for pottery glaze that explicitly contains lead. At some point, a discovery showed that small amounts of lead and pigment smeared on glass and fired made stained glass paintings possible. The earliest known examples of colored stained glass windows date to 800-820 (San Vicenzo Abbey excavation in Volturno, Italy.)  In medieval Europe, leading up to Antonio Neri's time, lead glass was used in mosaic tesserae and in artificial gems.

Finally, it is worth noting that Neri's childhood church in Florence, Cestello (now called Santa Maria Maddalena dei Pazzi), was then run by Cistercian monks. It was the Cistercian luminary St. Bernard of Clairvaux who, in the twelfth century, built the first church with large windows, urging, "The soul shall seek the light by following the light."

This post first appeared here 15 November 2013.

Report from Parnassus

 

Rafael - El Parnaso (Vatican, Rome, 1511)

Apollo on Parnassus, (fresco detail). 

In the spring of 1612, Italian glassmaker Antonio Neri finished writing L’Arte Vetraria, and the Holy Office of the Inquisition approved it for publication. The book of glass technical recipes passed the Church’s censors despite it containing a large number of alchemy related methods. Contrary to what we might imagine, they did not have any problems with Neri’s work; in fact, one bureaucrat commented that the book was full of useful information. Remember, this was at the same time that so-called sorcerers and witches were being tortured and executed around Europe. One big difference in this case was intent, or rather the perceived intent of Neri's writing. Another factor was his personal connections. The truth is that alchemy was something of a fad among the wealthy nobility, who used the equipment for everything from making rosewater, to distilling liquor, to quietly trying their hand at transmutation. 

To form a better sense of the public image of the chemical arts in the early seventeenth century, we can turn to the satirical critic Traiano Boccalini, who published a book of his own the same year as Neri. Ragguagli di Parnaso [Reports from Parnassus] was an immediate hit. In fact, it became so popular that he and his sharp tongue were forced to leave Rome for the comparative safety of Venice soon after its completion, and soon after that friends found him dead under suspicious circumstances. Initially, Boccalini had been on good terms with Church officials, but perhaps he had seen a bit too much of the institution's inner workings. Eventually, he became bitterly disillusioned and wrote Ragguagli as a collection of fictitious news-sheets. These were patterned after the letters that circulated widely as the forerunners of modern newspapers. His reports took place in the mythical state of “Parnassus,” which struck an uncanny resemblance to contemporary Rome. Its monarch, Apollo, struck an uncanny resemblance to the pope, as the princes of Parnassus did to cardinals, bishops and curia officials. Report LXXXIX is illustrative of what were the more practical fears over alchemy, in this case, some creative wealth building among the clergy. It gives a sense of alchemy’s public persona. Apparently, in real life, there was a crackdown by the Church on chemical apparatus, under the guise of concern for public health. Our author slyly suggests, in the very last line, that it may have had more to do with putting an end to clergy lining their own pockets. 

Apollo [the pope] Prohibits the Princes from the Use of Distillers or Alembics At Home: 

In the past few months here, various ailments have emerged in this state of Parnassus, which have caused in some an extraordinary fatigue with frequent agitation: in many a tenacious fever, a faint pulse and a monstrous appetite: in others an intense stomach ache with an ardent thirst.  

The doctors cannot find a single remedy. However, the true cause of these maladies, by decree of Apollo, was revealed before a recent meeting of the grand Asclepius [Society] of prominent Greek, Latin and Arabic doctors, where it was the subject of long and erudite debate. Because neither the enemies of the grand princes nor other eminent gentlemen were spared, it was doubted whether the sickness was caused artificially by powerful poisons. Furthermore, it is clear these troubles were not only happening nearby.  

And we see several modern princes put great study in their most excellent facilities to prepare in their alembics things other than rose water. They conceal subjects dangerous and heinous with their hidden machinations of poison. This cannot be allowed to be covered up; such a scandal must be exposed with the violence of a dagger.  

His Majesty, concurring with the opinion of the congregation, yesterday morning made a public speech, to issue a strict edict, which forbids princes of any color, from ever keeping distillation or alembic operations at home or outside. However, he allowed similar exercises in the hands of experimenters and herbalists. A thing being extremely foul is the minting of counterfeit money in the night and then by day covering so treacherous a crime by running shops openly making medals for the crown. 

In this piece, Boccalini crystallizes the complex social stigma carried by alchemy. Of all the practical tasks that could be performed in this art, the most notoriety by far was derived from the concept of turning base metals into gold. 

In a 1613 ms, Neri openly expressed his fear that true transmutation, in the hands of the masses was likely to collapse the economy. The Vatican’s concerns were more immediate: financial gluttony within the Church. Anyone with enough alchemical knowledge could produce convincing counterfeit money. Turning lead into gold was a theoretical issue; dealing with rogue counterfeiters was a real and immediate one. 

[1] Antonio Neri, Manuscript, Biblioteca Nazionale Centrale di Firenze: Ms. Conv. Soppr., B.3.16. Discorso sopra la chimica (che cosa sia, e sue Operazioni del R.[everendo] P.[rete] Antonio Neri Sacerdote Fio.o) (1613).
*This post first appeared here on 8 August 2014.

Galleria dei Lavori

 

Giovanni Stradano  (Jan van der Straet) 

Alchemy Studio, 1571
(Inside the Uffizi Galleria dei Lavori)

In 1560, Cosimo I, Duke of Tuscany, commissioned Georgio Vassari to begin construction on the Uffizi Palace in Florence. Two wings of the structure frame a long, narrow courtyard leading out to banks of the Arno River. Today it houses one of Europe's premier art museums, but its original design was as the central administration of the Medici government. The lower floor held offices of the regional magistrates, and the upper floor of the west wing (above the mint) held a variety of workshops highlighting Tuscan industry. Grand Duke Cosimo de' Medici built a glass furnace there, which he staffed with Muranese masters of the art. He won their expertise through long, hard negotiations with the doge of Venice. 

A 1571 painting by Giovanni Stradano is entitled the Alchemy Studio. It shows Cosmo's son, Francesco I, in the Uffizi surrounded by laboratory equipment and workers. Under the watchful eyes of a senior alchemist, he stirs a chemical preparation over a stove with intense concentration. The prolific glassware in this scene drives home the close relationship between glassmaking and scientific investigation.

By 1588 Francesco's brother, Ferdinando I de' Medici, formally declared this space the Galleria dei Lavori or 'gallery of the works'. There is no direct evidence that Antonio Neri gained his education in alchemy at this facility, but it makes a very attractive candidate. Of note to this story is that a demonstration was performed for Ferdinando de' Medici in Rome that purported to turn half of an iron nail into gold; the work of German alchemist Leonhard Thurneysser. In the 1590s, when Neri was being schooled, several accounts describe that the nail (chiodo) remained on display for some time in the Galleria. Neri mentions the nail in his Discorso and Thurneysser is discussed in a 1601 letter to the priest from his friend Emanuel Ximenes.

After Neri's death in 1614, his Medici sponsor, don Antonio commenced a search for the glassmaker's secret of transmutation, which Neri had promised. In testimony given by a royal goldsmith, who had, in July of 1596, witnessed a demonstration in which "gold" was made by Neri, he pressed the glassmaker, who told him that the transmutation was a technique learned from a German, done with ordinary vitriol.  

It is interesting to note that when iron is soaked in a solution of "blue vitriol" now known as copper sulfate, an ion exchange reaction takes place, where the liquid deposits copper and takes up iron from the nail. It would be well into the 18th century before this chemistry was adequately understood. What the royal goldsmith would have seen is  a dull iron nail turn the color of yellow metal before their eyes. Perhaps the goldsmith was not given the opportunity to further test the sample. 

Bianca Cappello and Francesco de Medici

 

19th century romantic depiction of

Bianca Cappello, Francesco de' Medici 

(with Don Antoni as a child.)

The story of 17th century glassmaker Antonio Neri weaves together closely with that of a Medici prince also named Antonio. The prince was six months younger, living quite a different life, yet holding many of the same interests. Don Antonio de' Medici was the eldest and only surviving son of the second grand duke of Tuscany. He became both Neri's employer and his benefactor. Don Antonio's own fascination with nature's secrets ran in his blood, a fascination that preceded him by at least four generations. His father Francesco and his grandfather Cosimo, both grand dukes of Tuscany, avidly pursued the vagaries of natural secrets. Cosimo had picked up the interest of alchemy from the notebooks of his own paternal grandmother, Caterina Sforza, as preserved by his father, Giovanni dalle Bande Nere. Don Antonio would carry on the family passion working in the laboratory built by his father on the north side of Florence, called the Casino di San Marco. Shortly after the prince settled in, priest Antonio Neri came to work in the Casino laboratory and there learned the craft of glass formulation. 

Evidence suggests that Don Antonio's mother. Bianca, was also fascinated by alchemy. Although specifics are hazy, she apparently cultivated relationships with women in the city's Jewish quarter who were well steeped in the concoction of various remedies and potions. Furthermore her family was involved in the glassmaking industry in Venice, another craft with close connections to chemistry.

By the time Don Antonio dusted off the cobwebs at the Casino and restarted the laboratory there in his early twenties, he had already experienced more than his share of misfortune. At the age of eleven, his life was suddenly changed forever when he lost both parents. Among many other implications, it meant relinquishing his future as grand duke of Tuscany to his uncle Ferdinando. Cardinal Ferdinando de' Medici had been visiting his brother, Grand Duke Francesco and his wife Bianca when they both became violently ill and died within days of each other in the fall of 1587. It was no secret that the brothers had running quarrels on a variety of matters from the cardinal's allowance to the way Francesco was running Tuscany. It was also no secret that Cardinal Ferdinando strongly disapproved of his older brother's wife, Bianca Cappello. She had earlier been the duke's mistress; they married in secret shortly after Grand Duchess Giovanna died in pregnancy. 

As soon as Francesco and Bianca's deaths were made public, rumors began to fly that the cause was poison in their food and not pernicious malaria, as pronounced by Ferdinando's own two doctors, Cini and Da Barga. Related rumors claimed that Don Antonio was an illegitimate child, or adopted, or even the product of witchcraft, none of which hurt Ferdinando's case for succeeding his brother as grand duke. The narrative was that Ferdinando had made a ruthless power grab, assassinating his brother and sister-in-law; it was a narrative that spread and gained momentum over the years, fueled by careless researchers and Victorian era romanticism. In some nineteenth and twentieth century history books, it was reported as all but fact. The poisoning of Ferdinando and Bianca has been the subject of theatrical productions, novels, poetry, paintings and a musical composition. Admittedly, it does have all the elements of a great story: Marriage for love in the aristocracy, sex, murder, intrigue, politics and religion. Truth be told, given the Medici family’s actual history, the story is not all that far-fetched, but it turns out not to be true, at least as far as modern forensics technology can determine.

 Controversy erupted in 2007 when a team from the University of Florence reported that they had unearthed what they presumed to be the long-lost (but partial) remains of Grand Duchess Bianca. Testing revealed a significant level of arsenic, leading some to give assassination another look. Others pointed out that arsenic was commonly used as an embalming preservative in this period. Meanwhile, a team at the University of Pisa confirmed that there are malaria pathogens in what are not disputed to be Francesco's remains, interred at the Chapel of Princes in Florence. 

Ferdinando's two physicians, Giulio Cini and Giulio Angeli da Barga, who were on the scene in October of 1587, reported that symptoms were identical in both patients. Modern forensics pathologists agree that those symptoms are entirely consistent with pernicious malaria. Furthermore, it was recorded that a few days earlier, Francesco and Bianca had ventured into a swampy area on a walk near the estate where they met their end. In fact, Francesco had lost two younger brothers and his mother to malaria, and I can personally vouch that Tuscan mosquitoes are nasty little creatures. If not for an insect bite, Don Antonio might well have become the third grand duke. As it was, Ferdinando took the reigns of power and Antonio Neri's father was appointed to be the new grand duke's royal physician, with Cini and da Barga his assistants.

Torricelli and Glass

Evangelista Torricelli

by Lorenzo Lippi, circa 1647

Evangelista Torricelli (1608–1647) is remembered as the inventor of the mercury barometer. Lesser known are a number of significant contributions he made to mathematics, astronomy and physics. There is no direct connection to the Florentine alchemist and glassmaker Antonio Neri—Torricelli was only a boy of six when Neri died—yet there are unmistakable echoes left by Neri that are amplified when we examine Torricelli’s time in Florence.   

In 1632, Torricelli wrote a letter to Galileo, which began a friendship that lasted until the famous astronomer died a decade later. In fact, Galileo invited Torricelli to stay at his house where they spent the last three months of Galileo’s life working together. If Torricelli had not heard of Neri before, perhaps he became acquainted through the copy of his book, L’Arte Vetraria that Galileo had on his bookshelf. Afterward, while preparing to return to Rome, Torricelli was intercepted by the Grand Duke of Tuscany, Ferdinando II de' Medici, who asked him to succeed Galileo as the chair of mathematics at Pisa. He was given a good salary and quarters at the fabulous palace in the center of Florence, that is now called the Medici-Riccardi.  

Historian Mario Gliozzi writes: “Torricelli remained in Florence until his death; these years, the happiest of his life, were filled with the greatest scientific activity. Esteemed for his polished, brilliant, and witty conversation, he soon formed friendships with the outstanding representatives of Florentine culture.” [1]  The ancient palace itself was largely empty in this period, inhabited by a handful of relatives, officials, intellectuals and artists connected with the Grand Ducal court. [2]

Among Torricelli’s companions at the palace were the three sons of Don Antonio de’ Medici, Antonio Neri’s long time benefactor. The boys, Paolo (1616-1656), Giulio (1617-1670) and Antonfrancesco (1618-1659) moved there in 1646. None of the brothers had personally met Neri, as they were all born shortly after his death, but they must have heard plenty about him growing up. As children, they had the run of the Casino di San Marco, the palace where Neri had made glass and pursued the secrets of alchemy. After Neri’s death, their father, Don Antonio spent significant time trying to hunt down Neri’s secret recipe for transmutation. Years later, when Giulio died in 1670, among his possessions were found a box of elixirs and “a booklet, entitled: Material of all the compounds of Priest Antonio Neri; there is a red dustcover, which says ‘experiments.’” [3] The materials were handed over to Jacinto Talducci, the Grand Duke’s chief chemist, and master of the new glassworks established in the Boboli Gardens, a man whom Torricelli depended on for glass. Talducci was also a veteran of the Casino di San Marco Laboratory; according to legend, as a boy he personally witnessed Neri’s transmutation of gold. Curiously, at Giulio’s death he was listed as living on Borgo Pinti in Florence, the same street on which Antonio Neri grew up. Also the same street where Galileo was tutored in  mathematics as a boy -- at the monastery where Neri's family attended church.

While in Florence, Torricelli took a great interest in optics. Again quoting Gliozzi:

[T]here is very good evidence of his technical ability in working telescope lenses, a skill almost certainly acquired during his stay in Florence. By the autumn of 1642 he was already capable of making lenses that were in no way mediocre, although they did not attain the excellence of those made by Francesco Fontana, at that time the most renowned Italian telescope maker. Torricelli had set out to emulate and surpass Fontana. By 1643 he was already able to obtain lenses equal to Fontana’s or perhaps even better, but above all he had come to understand that what is really important for the efficiency of a lens is the perfectly spherical machining of the surface, which he carried out with refined techniques. The efficiency of Torricelli’s lenses was recognized by the grand duke, who in 1644 presented Torricelli with a gold necklace bearing a medal with the motto “Virtutis praemia.” 

The fame of Torricelli’s excellent lenses quickly became widespread and he received many requests, which he fulfilled at a good profit. He attributed the efficiency of telescopes fitted with his lenses to a machining process that was kept secret at the time but was described in certain papers passed at Torricelli’s death to the grand duke, who gave them to Viviani, after which they were lost.

Gliozzi continues to describe that in 1924 one of Torricelli’s lenses was examined optically using the diffraction grating. “It was found to be of exquisite workmanship, so much so that one face was seen to have been machined better than the mirror taken as reference surface, and was constructed with the most advanced technique of the period.”

In addition to precision glass for lenses, Torricelli depended on Talducci and the grand duke’s furnace for scientific glassware; his experiments that demonstrated the measurement of air pressure required glass tubes, sealed at one end, two ‘cubits’ long (about four feet). They needed to be strong enough to be filled with mercury (which is very heavy) without breaking. It took his colleague Mersenne a couple of years (until 1646) to match the Florentines and obtain an acceptable tube from the French glassworks. 

Torricelli worked with former employees of the Casino di San Marco laboratory who knew Neri, he lived with Don Antonio’s three sons and he took a keen interest in glass; it seems impossible for him to be unaware of Neri and the echoes of his work in Florence.

[1] Mario Gliozzi "Torricelli, Evangelista" in Complete Dictionary of Scientific Biography. 2008. Encyclopedia.com.  http://www.encyclopedia.com/doc/1G2-2830904345.html

[2] 1609-1659 - The last inhabitants of Palazzo Medici http://www.palazzo-medici.it/mediateca/en/Scheda_1609-1659_-_Ultimi_abitanti_di_Palazzo_Medici_

[3] Covoni 1892, p. 193.

The Rise and Fall of Glass

 

"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.