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, September 28, 2018

Neri's Travels

“Roma,” Antonio Neri,
from Tesoro del Mondo (Neri 1598–1600).
The length and breadth of Antonio Neri's travels are far greater in thumbnail biographies and off hand remarks than can be substantiated by actual documentation. While stories of the glassmaker's travels through Europe abound, the truth of the matter is that only a small number of his movements have been verified through contemporary materials. But even if a minority of the wanderings attributed to Neri are true, then he certainly was a man of the world. Writing nearly two centuries after his death, historian Giovanni Targioni-Tozzetti claimed the priest left Italy to elude "thugs" in Florence who hounded him for the secret of transmutation. Tozzetti says he fled to England first and then visited Spain, Holland and France. [1] No evidence has yet turned up to support any of this. 

Other accounts say he "traveled all over Europe" and that he deceitfully posed as a "common assistant" in order to learn scientific secrets that he could not gain access to by other means. [2] One story I have heard making the rounds among glass workers is that Neri was chased to the "gates of Prague" by assassins. This is most likely confusion with a similar story about Venetian glassmakers leaving Murano without state permission to ply their craft elsewhere.

There are four cities in which Neri is confirmed to have been present: Florence, the city of his birth; Pisa where he worked at the glass furnace run by Niccolò Sisti; Antwerp, where he spent about seven years visiting his friend Emmanuel Ximenes and in Mechelen, at the Hospital of Malines, where he wrote about pioneering medical treatments in a letter to a friend back in Florence.[3] 

In addition, there are other locations that are strongly hinted at in various writings. In his Treasure of the World manuscript, Neri has an allegorical depiction in the form of a simplistic map showing “The Ways to Rome.” It depicts the walled enclave of the Vatican (see illustration) with various paths representing different chemical routes to transmutation. If nothing else, this leaves the door open to a personal familiarity with the eternal city. In his glass book, L’Arte Vetraria, Neri mentions a number of specific locations in northern Italy, but perhaps none as authoritatively as Venice. He comments about the materials and techniques specific to the glassmakers on Murano. There is little doubt that Neri was exposed to Venetian glass workers in Florence, Pisa and Antwerp, so they provide a perfectly plausible source for his knowledge of their distinctive techniques. This would be a sufficient explanation, except that there is also a letter written by his friend Emmanuel Ximenes, detailing a route for Neri's visit to Antwerp; a route that runs through Venice. Below is the passage from a letter, dated 5 December 1602. The glassmaker would be delayed by illness, but the following year he did make the journey. While it seems a good bet that he followed Ximenes' instructions that is another detail in need of confirmation.
Anyway, the lack of peace in these countries prevents me from recommending them for you to come or not, but if you make up your mind to come, God willing, you will have the same fortunes as we have. Besides, after your arrival, is not a marriage indissoluble, having no other bond than mutual affection? If you decide to come I would recommend that you should go with the courier from Florence to Venice, arriving in Venice in time that you would be able to accompany the merchants who come to the fair held in Frankfurt at mid Lent; you will stay there the length of the fair for fifteen days, which will not displease you for having seen it. After that, you would go in the company of other merchants to Cologne and then with them or others, by land or sea to Holland, ending up at this city. This sea, however, is nothing more than rivers. I recently went by land to Basel and from there by water ending here. But for Your Lordship,  who does not speak the German and Flemish languages, I would consider better the way that I say, with merchants from Venice to Frankfurt and then with others by water to arrive here. To this end, if you decide to come, upon giving me notice I will immediately send letters of recommendation to Venice to find a person who will help you to find company that must end up in Frankfurt and another for a friend in Frankfurt to get you started and perhaps it would be the same one with whom Guillelmo Reineri, servant of my brother Mr. Niccolò, came from here. Guillelmo usually goes to every fair by water up to Frankfurt, then back when it ends. He is close to me, a friend and very practical in his travels. This Renieri may give a report of the Frankfurt fair and also details of the voyage, as he made the outward journey for the fair last September. I shall send him a letter by means of my brother to give him the money on my account that would be necessary. But you should decide and advise me immediately, in order to go to Venice in time to find a group. I will wait for your decision, asking God to inspire the best . . .  [4]


[1] “E fatto con prestezza fagotto, la mattina all'aprir della porta uscì el di Firenze e se n'andò in Inghilterra. Girò la Spagna, Olanda, Francia e Germania…” [He packed in haste and in the morning opened his door, left Florence, and went to England. He toured Spain, Holland, France and Germany…] Targioni-Tozzetti 189, p. 149.
[2] See Rodwell 1870.
[3] Neri 1608.
[4] Ximenes 1601–11, 5 December 1602.
* This post first appeared here on 19 Dec. 2014.

Wednesday, September 26, 2018

Golden Yellow Glass

Yellow Neon Chandelier, 1995
Dale Chihuly.
(Columbus, Indiana Visitors Center). 
"Very few people know how to make colors like golden yellow and solid red well. These are difficult and troublesome in the art of glassmaking, since in making them you must stick precisely to the doses, the timing, the details and the materials as prescribed. The smallest error will cause everything to be ruined, and the colors to be irreparably spoiled. Therefore, you must be on guard not to make mistakes. [1]
So says Antonio Neri in his groundbreaking 1612 book of glass recipes, L’Arte Vetraria. Elsewhere he warns in several places not to add “tartar” to any glass destined for yellow pigmentation. Tartar was a common additive to boost the ‘sparkle’ of a glass because it contained a high level of potassium carbonates. These converted to potassium oxide in the melt, which has a higher refractive index than the usual glass flux, sodium oxide. However, his actual glass recipes tend to contradict this advice. 

Neri says of his “fern glass,” which is entirely potassium based:
…This frit can be given a wonderful golden yellow color provided there is no tartar salt within, as described in the caution, because then golden yellow will not emerge. This crystal is given to a golden yellow that is far more beautiful and pleasant than can be achieved in cristallo made with Levantine polverino salt and with this crystal unlike the other, every kind of job can be done. [2]
“Polverino” was a sodium based plant product used in many of Neri’s glass recipes, which he says was derived from the Kali plant grown in the Levant. The plot thickens when, for yellow, he recommends substituting ‘rocchetta’ another soda based Kali derivative. 

His primary recipe for golden yellow is #46, in which he reveals two ingredients responsible for the color, paradoxically, one of them, in direct contradiction to his previous advice, is tartar: “For every 100 pounds of [glass], add 1 pound of tartar from the dregs of red wine. Use large pieces well vitrified naturally in bottles of wine, because the powder is no good. Crush these raw dregs well, and pass them through a fine sieve. For every 1 pound of these dregs, add 1 pound of prepared Piedmont manganese…” [3] To this he adds the advice that “the powder is always given in parts and given [to the frit], not to the fused glass, because then it will not tint.”

He also offers advice to add more or less pigment depending on the intended use of the glass: more for thin items, less for heavier ones. “For larger [thick] spit beads, it is said that at Murano they reduce the dose of [wine] dregs and manganese by nearly half.”

For Neri’s lead glass, he uses a different combination, this time pairing copper sulfate with iron oxide: “Take 16 pounds of cristallo frit and 16 pounds of lead calx. Mix them well and pass them through a sieve. To this material, add 6 ounces of thrice cooked copper, made with flakes of the kettle-smiths [chapter 28], and 2 pennyweight of iron crocus made with vinegar [chapter 17].” He goes on to advise, “If it leans toward greenishness, add a little iron crocus, which will remove the greenishness and will bring out a yellow color of the most beautiful gold.

Yellow is one of several colors that iron oxide can form in glass, and is used frequently in low-fire pottery glazes. In that realm, it has a reputation as a difficult, unstable color, as Neri alludes to in his warnings. But in modern, higher temperature borosilicate glass, iron oxide is relied on for a nice yellow. In modern soda-lime glass, cadmium, titanium or the exotic praseodymium are more likely choices. They produced bright reliable color that is stable at the higher temperatures of modern operations. In lead glass, selenium is the modern favorite for yellow.

[1] Neri 1612, ch. 45.
[2] ibid, ch 5.
[3] ibid, ch 46.

Monday, September 24, 2018

Lead Crystal

Roemer type drinking glass c. 1677,
George Ravenscroft.
The entire fourth part of Antonio Neri's 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.

Friday, September 21, 2018

Veins of the Earth

Antonio Neri, "The Mineral Gold"
Neri 1598-1600 (Ferguson 67), f. 5r.
Over a decade before Antonio Neri wrote L’Arte Vetraria, the book on glassmaking for which he would become famous, he wrote an illustrated manuscript on the subject of alchemy. Begun around 1598 and completed in 1600, this is Neri's earliest known work, written very shortly after he was ordained as a Catholic priest. 

The illustrations are divided between technical depictions of chemical apparatus and allegorical images meant to show philosophical relationships within the natural world. Two of Neri's pictures from this latter group, respectively, show veins of gold and silver growing in the earth. The veins are depicted exactly like the arteries of an animal. In both pictures, they radiate out around fiery holes in the ground, what one might presume to be volcanos. Overhead the sun shines down on the gold and the moon over the silver. Further up in the sky, Neri shows the constellations associated with each metal; Leo the lion for gold and Cancer the crab for silver (his rendition looking more like a lobster).

It was no flight of fancy that mined metal and ore deposits were depicted as literal veins. It was widely thought these were living structures, which carried the earth’s nutrients. In one of Neri's final works, his 1613 manuscript Discorso, he explains the ancient theory that gold could occur as immature seed material, left over from the primordial creation. If properly nourished, this seed would mature and grow into the precious metal, and with the appropriate knowledge this natural process could be restarted, or accelerated and the gold could be brought to perfection by artificial means. 

Antonio Neri, "The Mineral Silver"
Neri 1598-1600 (Ferguson 67), f. 6r.
The idea that mined mineral deposits could regenerate naturally, if left to rest, is an ancient concept, one that persisted long past Neri’s era. In 1814, writing about tin mining in "On the Veins of Cornwall," William Phillips complained to the Geological Society of London, that armed with some current scientific knowledge, "nor would many miners […] believe, even to this day, in the regeneration of metals." Phillips quoted from an 1811 survey by
Tonkin, in Carew's survey of Cornwall: "Whether tin doth grow again, and fill up places which have been formerly wrought away, or whether it only seperateth itself from the consumed offal, hath been much controverted, and is not to this day decided." And  "whether—dead lodes—that have not one grain of tin in them—may not hereafter be impregnated,  matured,  and prove a future supply to the country, when the present lodes are exhausted, I think well deserves our highest consideration."  

At base, this is not superstition nor wild speculation, but rather considered judgments of thoughtful men making careful observations. Mines were often attended by acidic or other caustic liquids, either produced naturally or by washing operations, which leached out and dissolved various solubles. These liquids could sometimes dissolve metal out of ore and redeposit it elsewhere. Abandoned mines, it was noticed, could exhibit new crystal growth after a period of years or centuries. Today, the redeposition of minerals is a well accepted phenomenon, however, where it does occur it takes place not on a human time scale, but on a geological one, over millions of years.

*This post first appeared here in a slightly different form on 2 December 2013.

Wednesday, September 19, 2018

Knights of Malta

Fra Antonio Martelli, Knight of the Order of Malta,
Attrib. Caravaggio, c. 1608.
"Of me, Priest Antonio Neri, Florentine 1598." So starts the inscription on the first of 61 ink and watercolor illustrations in a manuscript titled "Tesoro del Mondo" [Treasure of the World]. It is the earliest manuscript known to exist by the respected glassmaker and alchemist, started when he was just twenty-two years old. Given the Church's rules and the typical length of training for ordination, twenty-two is about the youngest age possible for a priest. In fact, it is likely that the responsibility was granted to him mere months or weeks before the ambitious manuscript was begun, which he dedicates to the exposition of "all of alchemy." 

This scenario raises the intriguing question of which religious order would have taken on the sponsorship of educating a future priest as an alchemist; a mystery that remains unanswered to this day. Recently, we looked at two promising possibilities; the Canons Regular, and the Dominicans. Today we investigate a less conventional possibility: the Knights of Malta. The knights were ancient aristocratic military order that originated during the crusades and in Neri's time ran the papal navy. 

The Knights of Malta headed two churches in Florence and Neri can be connected to both. With the first, our priest has an indirect association. San Giovannino dei Cavalieri, (formerly called San Giovanni Decollato) is located a few steps from the Casino di San Marco, where Neri made glass at the beginning of the seventeenth century. His sponsor and owner of the Casino was Medici prince Don Antonio, whose daughter Maddalena later served as a nun at the associated convent. [1] The second church, San Jacopo in Campo Corbolini, is directly connected to Neri in a story recorded shortly after his lifetime. [2]

The following passage contains much that is contradicted by the facts, yet infused enough with the truth to make us wonder. Historian, courtier, genealogist and Florentine senator Monsignor Girolamo da Sommaia [3] recounted that:
M. Antonio who had died in Florence five or six years earlier and was from San Jacopo in Campo Corbolino,[4] said that he had the [philosophers] "stone," which he found in a pen-written book of secrets and took the paper and showed it to Casa (Agnolo Talducci della Casa, from the reign of Ferdinando I) who said what he was holding was sophistry, but that the cost was very little to try, so he tried it, and saying he succeeded, he told Casa and a goldsmith on the Ponte Vecchio, who did the first assay and later in his presence threw a bag of that powder into the Arno.[5]
A number of notebooks chronicle Neri's long working association with Della Casa at Don Antonio de' Medici's laboratory. These and other documents cast considerable doubt on the veracity of Sommia's story. Nevertheless, individual details do ring true. Of particular interest is the name of the church, San Jacopo in Campo Corbolini. It still stands today, a block west of the mercato centrale in Florence. The Knights Templar occupied it since 1256 and when that order died out, the Knights of Malta took it over. Neri's affiliation may have been through his work for Don Antonio, who belonged to the order. Another possibility is that Neri was attached to the knights through his father's connections at court. The order maintained a great deal of independence, reporting directly to the pope and curia. Their main presence was on Malta, Neri was not a knight but he could have occupied a place in their clergy.

The knights followed the rule of Augustine and enjoyed a close relationship with the Augustinians. The order traces its roots to the crusades [6] and has various associations with alchemy, notably George Ripley. [7] The fifteenth century English physician and alchemist was ordained into the Canons Regular of Saint Augustine, but he later joined the Carmelites. He is purported to have used gold produced through alchemy to help finance the Knights of Malta in the war with the Ottoman Empire. [8] Folklore maintains that Ripley learned transmutation as part of his Italian schooling in alchemy.

[1] Luti 2006, pp. 171, 172.
[2] See Targioni-Tozzetti 189.
[3] Girolamo da Sommaia (1573–1635). He served as provost of the university (studio) at Pisa and prior of the convent church of the Knights of Saint-Etienne in the years 1614–1636. He was also a friend and supporter of Galileo.
[4] Today, this church is called S. Jacopo in Campo Corbolini. It was founded in 1206.
[5] Related in Targioni-Tozzetti 189, thanks to Maria Grazzini for pointing me to this passage.
[6] Known variously through history as the Knights Hospitaller, the Knights of Rhodes, the Knights of St. John of Jerulsalem and the Knights of Malta.
[7] Sir George Ripley (ca. 1415–1490), Bridlington, York. Cf. Rampling 2008; McCallum 1996.
[8] Fuller 1840.

Monday, September 17, 2018

Alchemist Cardinal

Portrait of Francesco Maria del Monte
Ottavio Leoni (1578–1630)
In the early seventeenth century, Cardinal Francesco Maria del Monte served as the unofficial Florentine cultural ambassador in Rome. He regularly entertained visiting dignitaries and represented the Medici family's interests within the Vatican. He was an avid art collector, glass enthusiast and amateur alchemist.  He was a patron to the artist Caravaggio, to the astronomer Galileo and a dear friend to Antonio Neri's employer Don Antonio de' Medici.

The strong bond of affection between Don Antonio and Cardinal Del Monte is clear from their extensive correspondence and gifts to each other.  In addition to their passion for alchemy, the two shared a strong interest in glassmaking technology. There is a chance that the cardinal met glassmaker Antonio Neri in Florence; in 1602 he visited the Casino di San Marco, where the glass foundry was located and he returned in 1608, although by then Neri was in Antwerp. Del Monte's biographer Zygmunt Waźbiński offers, "It is very likely that Cardinal Del Monte, with his interest in glass, had known then (in 1598) the [future] author [Neri] of L'Arte Vetraria." [1]

Del Monte collaborated with Niccolò Sisti, the grand duke's glass foundry master at Pisa, where Neri also worked for a time. Sisti often provided Del Monte with glassware for Medici customers within the College of Cardinals in Rome. The cardinal's patronage also brought many glassmakers in Rome to the appreciation of the papal court.  After his death, Del Monte's will shows that at his main residence, the Palazzo Madama, he maintained an entire room, "gabinetto dei vetri" [cabinet of glasswork] that housed five hundred pieces of glassware. It cannot go without mention that he was also the proud owner of what has become one of most celebrated pieces of ancient glass, now referred to as the Portland Vase.

There are indications in Neri's 1600 manuscript that he visited Rome. If so, it is hard to imagine him not seeking an audience with the cardinal, either at his villa on the Pincio,  overlooking the city or at the Palazzo Madama, now offices of the Italian Senate. The palazzo was appointed in fabulous luxury and arranged to accommodate a constant flow of dignitaries from around the world. The villa, on the other hand, was where the cardinal's alchemy laboratory was located. This was a more secluded retreat where the cardinal could entertain guests with more discretion.
   
Michelangelo Caravaggio, c. 1597
Casino Ludovisi.
As the sixteenth century ended and a new one dawned, Del Monte sheltered the rough-and-tumble painter Michelangelo Caravaggio, whom he set up with an in-house studio and an allowance. However, in 1606, the master of Realism fled Rome after reportedly murdering a tavern waiter over a tennis wager, but not before executing his only known fresco on the vaulted ceiling of Del Monte's own alchemy laboratory. Looking out over Rome, on the panoramic Pincio, in the Villa that later became the Casino Ludovisi and is now known as the Casino dell'Aurora, Caravaggio put his brush to work. 

According to Gian Pietro Bellori, the early biographer of artists, Caravaggio executed the oil painting sometime between 1597 and 1600. [2] Depicted in the mural are the three brothers Jupiter, Neptune and Pluto: the masters of the universe. The image is a double allegory of the three basic chemical substances of Paracelsus (salt sulfur and mercury) and the four Aristotelian elements (air, earth, water and fire). Jupiter with the eagle stands for sulfur and air, Neptune with the seahorse stands for mercury and water and Pluto with the three-headed dog Cerberus stands for salt and earth. Jupiter is reaching out to move the central celestial sphere in which the sun (fire) revolves around the earth. [3] 


The villa was a relatively secluded retreat where the Cardinal could entertain guests discretely, including his friend Galileo–Del Monte and his older brother Guidobaldo helped land Galileo the chair of mathematics at the university in Pisa. This is also where Galileo demonstrated his telescope for interested dignitaries in Rome. It would be interesting to hear the astronomer’s comments on Caravaggio's tribute to heliocentrism.

[1] Neri 1612.
[2] Bellori 1672, pp. 197-216.
[3] Wallach 1975, pp. 101-112.

*The material in this post first appeared in a different form on  27 Nov. 2013 and 4 Jul. 2014.

Friday, September 14, 2018

Bibliomaniac

Broadway Tower, Worcestershire.
The home of Phillipps' Middle Hill Press
In 1612, Antonio Neri published his famous book on glassmaking, L'Arte Vetraria. [1] The venture was bankrolled by Medici prince Don Antonio for whom Neri had worked as an alchemist and glassmaker in 1601 and possibly a couple of years earlier. The printer was Giunti, the venerated Florentine family of typographers who set up their first press in Venice a century and a half earlier. In Neri's era, they operated as the de facto press for the grand dukes in Florence and they are still in business today.

Neri's book was noticed almost immediately; in a 1614 letter addressed to Galileo, Roman Prince Federico Cesi practically begged his astronomer friend to send a copy. [2] Cesi was the founder of the "Accademia dei Lincei" [Society of Lynxes] a group of naturalists who formed an early version of what would later be called 'scientific societies.' The book was tailor made for such groups who were interested in performing their own experiments, however, sales did not exactly catch fire among the public. 

A few decades later, another scientific society was formed in London, with a charter signed by no less than King Charles II. The Royal Society really gave Neri's book a major boost when in 1662; founding member Robert Boyle commissioned Christopher Merrett to translate the work into English. [3] A year earlier, a second edition had been printed in Florence and a year later, another Italian edition appeared in Venice. [4]

From there, the book took off, sprouting multiple new translations in the Netherlands, Germany, France and Spain. There are many interesting stories of how the book spread across Europe; one of the most fascinating deals not with the book itself but with a publisher. Without any doubt, Sir Thomas Phillipps was the most colorful of any of Neri's printers. In 1826, Phillipps' press issued a reprint of Merrett's original English translation, which was by then over a century and a half old. [5]

By the 19th century, L'Arte Vetraria, or "The Art of Glass" as it was dubbed in English, had passed its prime as the bible of glassmakers. As one would expect, methods and technology had matured considerably over the intervening two centuries. Nevertheless, Phillipps recognized its importance. He was also a bit eccentric. As a child, by his sixth birthday, he already owned over a hundred books; his grand ambition was to own one copy of every book ever printed, a quest he carried into adulthood. He was born in Manchester, the product of a clandestine relationship between a textile baron and a woman other than the one to whom his father was married. Nevertheless, he appears to have been well cared for and inherited what Wikipedia reports was a "substantial estate." [6] A fortune that he promptly started to whittle away, spending lavishly on books and manuscripts. He attended University College Oxford and within a few years, he was made a fellow of the above-mentioned Royal Society. 

Depending on where you stand, Phillipps was a classic example of British eccentricity, a brilliant and dedicated preservationist or a completely obsessed crazy-man. Possibly all three. By the end of his life, he had amassed an estimated sixty thousand manuscripts and forty thousand books. At the time it was the largest such private collection in the world. He housed his treasure in a castle that he had built for the purpose, Broadway Tower, in Worcestershire (see photo above). It is said that he would walk into various bookstores and buy the entire stock; his agents around Europe provided a steady stream of new material. Apparently, he himself possessed a sense of humor about his odd obsession, coining the term "vello-maniac" (referring to the vellum bindings common to many books of that period).

The story does have a darker side, albeit with a silver lining. In 1842, Phillipps started collaborating in research with James Halliwell, then an undergraduate at Cambridge studying Shakespeare. Halliwell became romantically involved with Phillipps eldest daughter Harriett, but Phillipps refused consent for them to marry (which they did anyway). Meanwhile, Phillipps had run through the family fortune and started to borrow heavily. He developed paranoia against Halliwell and vowed that he would never gain control of the collection. He entered negotiations to donate the books and manuscripts to the British Library, but his conditions were unpalatable and a deal was never reached. He wanted to stipulate that the order of books should never be reshuffled and that no Roman Catholic, especially his son-in-law, ever be permitted to touch or view the collection. He became so fearful  about Halliwell that he hired 250 men to move the collection, which took two years, at which point the abandoned castle started to fall into ruins. 

In the end, Phillipps died at the age of 79 in 1872. After a court decision, Harriett did inherit her father's collection and Halliwell did gain control. The silver lining is that the two undertook to carefully disperse the collection to some of the most prestigious libraries in Europe. This project took multiple generations to finish. In fact, the final parcel of books from the Phillipps collection sold at auction in 2006, at Christie's.

[1] Neri 1612.
[2] Cesi 1614a, 1614b.
[3] Neri 1662.
[4] Neri 1661, Neri 1663.
[5] Neri 1826.
[6] "Thomas Phillipps" Wikipedia, http://en.wikipedia.org/wiki/Thomas_Phillipps 
* This post first appeared here on 5 Oct 2014.

Wednesday, September 12, 2018

Thomas Edison's Lady Glassblowers

Fig. 1. 
Sealing the Glass Socket and
Carbon Filament into the Flask of an Incandescent Lamp.
"We will next turn to the glass-blowing department, where
hundreds of girls are employed in all the delicate and skillful 
manipulations involved in the glasswork of these lamps"
-Henry Morton, Scribner's Magazine, Vol. 6, 1889
On a cold Monday afternoon in December of 1888, Thomas Edison, his wife Mina and their children arrived in Akron, Ohio, on the 12:17 train. They had traveled from their estate ‘Glenmont’ in West Orange, New Jersey, to visit Mina’s parents for the holidays. That same evening, after dinner, Edison and his father-in-law, Lewis Miller, donned winter coats and walked to a nearby station of the Akron Electric Light Co. where they inspected one of Edison’s dynamo generators that had recently been installed. The dynamo was wired by dedicated copper lines to ‘Oak Place’, Miller’s residence. Upon returning to the house, the family assembled on the third floor, along with a newspaper reporter, where a “mammoth Christmas tree” stood. That year, the tree was adorned with ornaments, tinsel, and also a special addition: forty incandescent lamps that, with a flick of a switch, blazed to life.[1] There is every chance that each of those forty lamps was crafted by female hands at Edison’s Harrison, New Jersey, factory.


Early on, Edison decided on a female crew of flamework glass artisans to perform the delicate manipulations of assembling and finishing the incandescent lamp bulbs, (fig. 1). These specialists crafted the glass parts of the lamps in a complex series of steps. The ‘stem’ makers formed a glass seal around the electrical wires that held the delicate filament in place. The ‘tubulators’ put a small hole in the top of the bulb and attached the glass tubing used to pump the air out of the bulb. Mating the stem to the bulb in an air-tight seal without cracking or damaging either was an art unto itself. All the while, workers needed to adapt on-the-fly to continual changes in materials, procedures and tools as the bulbs evolved and improved. What is known, is that in the early days,  production took place at the laboratory in Menlo Park. As demand for the lamps started to explode, a “shed” for the glass work was built and then expanded. Because of the rural location of the laboratory, there was a continual problem of recruiting qualified workers. Around 1880, Edison turned to the employment of school-aged girls and boys to fill the labor shortage. Here he got a first hand look at what they were capable of. The use of women and girls for this glass work was a tradition that continued for nearly five decades, through the transition into General Electric Co., right up until the work was fully automated.


It was a year earlier, in the spring of 1879 that Edison first made the announcement that he was ready to begin producing electric lamps. Newspapers at the time gave great credit to a German glassblower working for Edison, for bringing the inventor’s research to fruition. This was Ludwig Boehm. He previously worked for Heinrich Geissler in Bonn, Germany, producing electrical discharge tubes and vacuum pumps.[2]  Boehm possessed the glassblowing skills to quickly whip out one test lamp after another, but he also knew how to make the coveted vacuum pumps invented by Geissler. These were the leading edge of vacuum pump technology, far faster and more efficient at evacuating the air out of the lamps than other methods of the time. Edison’s achievement would have been impossible without Geissler’s work and it was Ludwig Boehm, the glassblower, who was the conduit.

By 1882, a new ‘Lamp Works’ factory was ready in Harrison, near metropolitan Newark. It had more floor space than they could possibly ever use, or so they thought. By 1889, Henry Morton, the president of Stevens Institute of technology wrote, “Hundreds of girls are employed in all the delicate and skillful manipulations involved in the glasswork of these lamps.”[3]


Fig. 2.
Laboratory notebook entry
signed solely by Mina Edison.
Edison kept a series of laboratory notebooks documenting experiments and potential solutions to problems, and for the lamps there were many problems. The entries are often signed by Edison himself or his assistants. It is interesting to note that for a period, his wife Mina co-signed some of Edison’s entries and several pages appear in her name alone. This shows her active participation at some level in events of the laboratory.[4] Fig. 2 shows an example of a page signed by Mina Edison, Dated 23 March 1886 with three diagrams of lamps. The top diagram is accompanied by text reading “Make lamps of all kinds of glass and list conductivity.” The next diagram shows a bulb with a special electrode off to the side. The text reads “polished silver. Also one of polished hard rubber.” The third diagram shows a lamp with two filaments and appears to read “copper filament to take out curr[ent] 10-” While the intent of these experimental setups may be lost, what is clear is that she possessed a working understanding of how the lamps functioned and she was proficient at circuit diagrams. Whether she influenced the decision to use female glass workers is an open question.


To become one of Edison’s glass technicians meant steady work in a booming industry, it also meant a first-hand introduction to divisive labor problems common to factories at the end of the 19th century. In the summer of 1889, the general manager of the lamp works took a trip to Europe and, based on British glass blowing practices, he ordered his superintendent in Harrison to immediately cut pay and institute a list of new work rules. The superintendent procrastinated, knowing a disaster in the making when he saw one. Upon the manager’s return in October, the superintendent was fired and the new rules and wages were posted. “The workmen immediately commenced to walk out, and it is likely that the entire force of two hundred will strike” wrote one reporter.[5] Four weeks later, the papers announced that “The girls employed in Edison’s lamp works at Harrison, N J, will go on strike today because of a reduction in wages.”[6] Four years later, an unrelated incident at the lampworks made the papers. It illustrates that even with a good work record and no problems with management, simply getting in through the front door unscathed was not a given. “There was a small riot at the Edison Lamp Works in Harrison, this morning, between several hundred men who were waiting about the gates of the establishment for work. Some objected to the presence of a number of Polish Jews and a free fight ensued, which resulted in a number being badly bruised. The police dispersed the crowd.”[7]


Fig. 3.
Wanted ad for Edison’s Harrison Lampworks factory.
The Boston Globe (Boston Massachusetts)
22 June 1894, Fri., p. 9.
Through it all, the business continued to expand by leaps and bounds. A continual stream of “wanted” advertisements ran in papers as far away as Boston (Fig. 3.) In 1896, Harper’s Magazine reported that  Edison’s lamp factory at Harrison employed “several hundred girls and men” turning out over six-million lamps per year.[8] Even with long hours and partial automation, the line would require at least a couple-hundred glass workers for the delicate hand-work necessary in order to produce what amounted to a new lamp finished every two seconds on the clock.[9]


In the early 1900s the processes for making the lamps was further automated, with women still running much of the equipment. By 1903 a single worker could turn out 600 completed bulbs per day.[10]  By 1912 the Harrison plant employed a total of 4000 workers. In 1918 the women glass workers at the plant met to discuss forming their own union in order to institute an apprentice system to ensure the trade remained healthy.[11] Ultimately the entire lamp factory was closed in 1929 and the work was distributed to more modern and fully automated facilities around the country.[12]


Fig. 4.
Finishing work by women on tungsten lamps, c.1927.
(Shortly before the manufacture of lamp bulbs was fully automated)
Notice the striking similarities to fig. 1. above, from
the same facility, 40 years earlier.
The individual women and girls who worked for the electric lamp factory in Harrison can be traced to some extent through census records. A survey of the 1900 US census found over a hundred female respondents listing the Edison Lamp Works as their place of employment [13] The oldest was Elizabeth Stultz aged 45, the youngest Tillie Glinik just 13. There were a number of sisters there working glass side-by-side. Mary and Carrie Wright were 26 and 16 respectively, while Barbara, Christina and Annie Etzel were 19, 18 and 17.[14]


There is also evidence that the use of female glassworkers for Edison carried overseas to his British lamp making operation. As an 18-year-old, Florence Small who lived in a suburb north of London, worked making glass ‘stems’ for the Edison and Swan Electric Light Company (Royal Ediswan). In 1911, she worked at their Ponders End facility in her hometown of Enfield. She thought enough of the experience to include that detail in her will, fifty years later.[15]

Those forty lamps on the Miller’s Christmas tree in 1888, along with millions of other lamps were created by the skilled female flameworkers of the Edison and later General Electric lamp works in Harrison. It is quite a legacy that from the time of the introduction of electric lamps in 1879, all the way to the invention of television in 1927, the delicate glasswork of the electric lighting industry was firmly entrusted to the competent hands of women.


[1] “A Talk With Edison”, The Summit County Beacon (Akron, Ohio), 2 Jan 1889, Wed, Page 7
[2] “A Very Skillful Glass-Blower” Chicago Tribune (Chicago, Illinois), 4 January 1880, Sun, p. 10. In US Census records and laboratory notebooks Boehm spells his own name “Ludwig K Böhm”. In later life, he reinvented himself as a patent attorney in New York.
[3] Henry Jackson Morton, “Electricity in Lighting” Scribner’s Magazine 1889 vol. VI, pp. 19-23 [compiled, pp. 176-200], (Charles Scribner’s Sons: New York) p. 192.
[4] 03/18/1886 Edison, Thomas Alva -- Technical Notes and Drawings (Edison, Mina Miller (Mrs Thomas A.)) Incandescent lamp [N314] Notebook Series -- Fort Myers Notebooks: N-86-03-18 (1886) [N314003; TAEM 42:815] Courtesy of Thomas Edison National Historical Park.
[5] The Nebraska State Journal (Lincoln, Nebraska), 12 October 1889, Sat. p. 4.
[6] The Brooklyn Daily Eagle (Brooklyn, New York), 11 November 1889, Mon. p. 4.
[7] “Edison Lamp Works Riot.” Reading Times (Reading, Pennsylvania), 5 Dec. 1893, Tue. p. 4.
[8] R. R. (Richard Rodgers) Bowker “Electricity, a Great American Industry”, Harper’s Magazine, Oct 1896, vol. 32, p. 710.
[9] In 1892 Edison began to automate the process of forming the outer bulbs, ultimately farming the work out to Corning Glassworks.
[10] John W. Howell And Henry Schroeder, “History of the Incandescent Lamp” (The Maqua Company: Schenectady, New York ,1927), pp. 165-172.
[11] “Have Mass Meeting of Lamp Works Employes” (sic.), The Fort Wayne Sentinel (Fort Wayne, Indiana) 31 December 1918, p. 3.
[12] In 1932 the Harrison factory was re-purposed for the Radiophone Corporation of America. RCA, which produced electronic tubes until 1976. The site was ultimately leveled and is now home to a shopping mall.
[13] Combinations of search terms targeted females working at the Harrison, New Jersey Edison/General Electric Lamp Works. Women found working there, but not listing a specific profession could have worked non glass blowing jobs. Conversely, many who were glass workers at the plant left the census field for 'employment' blank, or were not asked by the census taker and therefore not found in the search.
[14] No candidates could be found in the 1880 US census, and the 1890 census was largely destroyed in a fire at the Commerce Dept. in 1921.
[15] Probate details for Florence Small provided by https://www.terrys.org.uk/charts/c/crack301.htm


Fig. 1: Sealing the Glass Socket and Carbon Filament into the Flask of an Incandescent Lamp. 1889
Fig. 2: Laboratory notebook entry signed solely by Mina Edison.
Fig. 3: Wanted ad for Edison’s Harrison Lampworks factory. The Boston Globe (Boston Massachusetts) 22 June 1894, Fri., p. 9.
Fig. 4: Finishing work on tungsten lamps, c.1927.

Monday, September 10, 2018

The Paracelsans

Image of Paracelsus
In the late sixteenth century, the writings of an obscure physician started to become very popular around Europe. Born in 1493 with the name of Theophrastus von Hohenheim, "Paracelsus"[1] was the son of a German physician living in Switzerland. Before marriage, his mother worked in an abbey hospital. Paracelsus took a degree in medicine from the university at Ferrara and proceeded to practice medicine as he wandered through Germany, France, Spain, Hungary, the Netherlands, Denmark, Sweden, Poland and Russia. 

Paracelsus died in 1541, nearly half a century before the various pamphlets he wrote started to be noticed and reprinted. In his lifetime he was not honored, but hounded out of one European city after another for defying traditionally accepted medical practices and insisting on doing things his own way. He was known for somewhat difficult personality, and the gloomy but steadfast conviction that the world would shortly come to an end. Today he is celebrated for diagnoses based on careful observation of nature, and of his patients actual symptoms, a radical departure from the norm for his time. 

By the end of the sixteenth century, his writings were being circulated among the intelligentsia of the Florentine royal court in Italy. His opinions extended not only to medicine and anatomy, but also to alchemy, botany, pharmacology, astrology, and what would later be called psychology. Paracelsus' philosophy was a powerful influence on the education of Antonio Neri in the discipline of alchemy.  Neri's father was the royal physician to Florentine Grand Duke Ferdinando de' Medici, and almost certainly did not subscribe to Paracelsan ideas, but Antonio seems to have taken a different path. His benefactor, Prince Don Antonio de' Medici was a confirmed Paracelsan.

By the time Neri's book on glassmaking appeared in 1612, the priest counted himself a devoted Paracelsan spagyricist and he as much as says so. In the book's introduction, he holds out the future possibility of publishing “the experience of my endeavors over many years, working in diverse parts of the world […in] the chemical and spagyric arts.” [2] Paracelsus had pioneered two new disciplines that he named "iatrochemistry" and "spagyrics." Iatrochemistry dealt with the use of minerals and chemicals in medicine; spagyrics made use of plants and their extracts. Here we get a hint that Neri's true passions lie beyond the formulation of glass. Speaking about the potential of chemistry in medicines, also in the introduction, he writes, "These are matters of nature to which I believe there is no higher calling in the service of humanity." The same techniques and terminology used to produce medical remedies shows up in Neri's glass formulations. Twice, he refers to ingredients as "medicine," [3] which he adds to the glass melt in "doses." He also uses the somewhat specialized apothecary's term 'ana', [4]  which means "in equal parts." 

Paracelsus coined the word "spagyric" in his book Liber Paragranum, [5] where he argues medicine should be based on the physical laws of nature alone. The word derives from two Greek terms: spao meaning to separate and ageiro meaning to combine. The underlying philosophy recurs throughout the history of alchemy. To enhance the special properties of a plant, break it down, to its separate constituents, then purify each and recombine them for a more potent product. 

Herein lay the bones of Neri’s empirical methodology with glass; one built on the processes of reduction, purification and recombination. These methods appear throughout his technical recipes. Neri utilizes the method with both plant and mineral ingredients, in the preparation of basic materials and pigments and throughout his medicinal work. You could say that these very techniques and the resultant near mania he developed for purification are responsible for the high reputation of his glass formulas. His colors were bright and clear beyond what was produced by typical preparation by artisans of his time. 

Around 1600, documented in surviving letters from his friend, Emmanuel Ximenes, the two men discuss Paracelsus, but do so carefully since it is still a rather controversial topic. [6] By 1608, Neri seems a bit more relaxed, writing to a Ximenes nephew that he had cured diseases using the "grandissima meraviglia" (wonderfully grand) methods of Paracelsus. [7]

Mere months before his own death in 1614, Neri wrote a small tract titled Discorso. The full title translates to 'Discourse on Chemistry, What it is, and its Operations'. [8] In it, he "manifests right from the outset his adherence to the Paracelsan doctrine, which is not restricted to inorganic chemical operations involving the transmutation of metals, but has broader applicability to the field of medicine." [9] Neri begins:
The operations belonging to chemistry do not only, as some estimate, involve the transmutation of metals. It is a much more universal art, which in some ways also embraces medicine (or at least it comes very close in assisting) and it can be defined. It is an art, which resolves and reduces all ‘mixed bodies’ [corpi misti] into their primary elements, it searches out their nature and separates the pure from the impure and it makes use of the pure to perfect these bodies and even to transform one body into another. [10]
History has mostly remembered Neri as a glassmaker, but his own philosophy was a bit different. He considered himself first and foremost an alchemist and his art—the art of chemistry—was a discipline that embraced metallurgy, glassmaking and medicine. 

[1] often referred to as Philippus Aureolus Theophrastus Bombastus von Hohenheim, this concatination was not used to refer to himself. for a fascinating discussion see Thony Cristie's post here: https://thonyc.wordpress.com/2012/05/01/whats-in-a-name-2/
[2] Neri 1612, p. vii.
[3] Neri 1612, pp. 40, 104, medicina; p. 9, dose and throughout. 
[4] Neri 1612, p. 98 ana
[5]Opus Paragranum, written in 1529/30 not published until 1565. Cf. Paracelsus 1565.
[6] Neri 1980, pp. xlii–xliii, lix. In his letters, Ximenes is careful about references to Paracelsus. 
[7] Neri 1608; Zecchin 1987–89, p. 157. “… che già stava in casa il s.r. Zanobi Bartolini, che mostra gl’ effetti di mali da lui guariti secondo gli ordini Paracelsici di grandissima meraviglia…” [that previously when in the house s.r. Zanobi Bartolini showed the effects on sicknesses that he healed using the instructions of the great and marvelous Paracelsus ....].
[8] Discorso sopra la Chimica, che cosa sia, e sue Operazioni, Neri 1613.
[9] Grazzini 1983, p. 221. 
[10] For the original Italian, see Grazzini 2012.

Friday, September 7, 2018

Neri's Other Ruby Glass

Rhodochrosite, from the Sweet Home Mine, Colorado.
Antonio Neri is widely recognized for publishing a recipe for the coveted and difficult gold ruby glass. "Rubino," as it is sometimes called, achieves a deep ruby red color utilizing only powdered metallic gold as a colorant. Perhaps because of the notoriety of that prescription, Neri’s other transparent red glass is hardly known. His recipe #120 describes a deep red pigment based on manganese. Today manganese takes its place on the periodic table as an elemental metal, but in the early seventeenth century it had not been isolated from its mineral ore. What Neri calls manganese was actually its oxide, which occurs as a black powdery material. Its effects in glass have been known since the early Egyptian dynasties and before that, as a pottery glaze. By itself the oxide produces a tint often likened to violet or amethyst. In small quantities, it is used to neutralize the slight green tint introduced by iron impurities in clear glass. 

To make his ruby red pigment, Neri starts with high quality manganese oxide from Piedmont and processes it through several alchemical operations. I will not be delving into the chemistry in detail here, suffice it to say that he comes close to synthesizing a highly unstable explosive, the likes of which was not "discovered" for another two centuries. It is a striking illustration of how technical ability can be in place long before theory catches up, in this case thankfully so. 

The pigment he did succeed in making is for now a mystery. Manganese carbonate, which can form ruby red crystals might fit the bill, except that it decomposes at the temperatures of molten glass. It occurs in nature as the mineral rhodochrosite as seen above. [1] Below is Neri's recipe for "Transparent Red in Glass" from his 1612 book L’Arte Vetraria. Most of the terminology is straightforward, with the exception of a few terms. 'Porphyry' is a hard granite used for grinding stones. 'Reverberation' is indirect radiation in a furnace, where the heat is reflected from the walls. 'Sublimation' is when certain materials vaporize directly from a solid form and recondense without passing through a liquid phase.
Grind manganese impalpably, then mix it with an equal amount of refined saltpeter and put it into a clay pan set to the fire, reverberating and calcining it for 24 hours. Take it then and wash its saltiness away with warm common water. Once separated from the salt, let it dry. It will be a ruby-red color. With this, mix an equal weight of sal ammoniac and grind them together over porphyry stone with distilled vinegar, which they will soak up. Leave this alone to dry and then put it in a retort with a wide body and a long neck. Heat it in sand for 12 hours to sublimate. 
Then break up the glass. Take all the deposits in the neck and body of the retort and mix it with the residual remains in the bottom. Weigh it and combine it all with as much sal ammoniac as was lost in the first sublimation. Grind everything together over the porphyry stone, with distilled vinegar for it to soak up. Then put it in a retort to sublimate as above. Repeat this sublimation, in this manner, many times until in the end, the manganese will all remain fusible in the bottom. 
This is the medicine that tints crystal and pastes in a diaphanous red color and a ruby red as well. Use 20 oz of this medicine per ounce of cristallo or glass, but more or less may be used accordingly to govern the color. The manganese should be the very best from Piedmont, so that it will have the effect of tinting the glass a beautiful ruby color and be a sight of wonderment.
[1] Manganese carbonate, MnCO3.

Wednesday, September 5, 2018

Lake of Flowers

'The Miracle of the Immobility of Santa Lucia'
Leandro Bassano, using Florentine lakes.
In the final part of Antonio Neri's 1612 book on glassmaking, [1] he presents several recipes that are devoted to pigments for painting. His intention for including them is for their application on glass objects, but these were the same materials used in general by fine artists in the early seventeenth century. 

In his recipe #110, the Florentine priest gives a wonderfully simple method to extract the color from common flowers. The term for these pigments is "lakes." Once obtained, the pigments were often used to dye a powdered carrier material in order to give them more body and behave like other paint. From there they might be mixed into egg-tempera, varnish or oil depending on the application. It is likely that Neri used similar pigments for the illustrations in his 1598 manuscript.[2] Here is his recipe in its entirety: 


A Way to Extract the Lake [3] and Color for Painting, from Orange Blossoms, Red Poppies, Blue Irises, Ordinary Violets, Red Violets, Carnations, Red Roses, Borage Flowers, Day Lilies, Irises, and From Flowers of Any Desired Color and the Greens of the Mallow, the Pimpernel and All the Plants. 
Take whichever flower you want, of any color you want, or even a [green] plant. If it will rub green from a leaf onto white paper staining it with color, then it will be good. The plants and flowers that do not show this effect are no-good. Put ordinary aqua vitae into a glass urinal, with a cappello [alembic cap] for its cover, making sure the said crystallo cap is as wide as possible. 
Into this cap, pack the leaves [or petals] of any flower or plant from which you want to release and extract the tincture. Now lute the mouth joint of the cap. Fit a receiver to its snout and lute that joint. Give it a moderated fire so that the volatile part [alcohol] of the aqua vitae rises into the alembic, and falls down into its volume upon the petals of the flowers, extracting the tincture. 
In time, drops will run down the snout of the cap into the receiver, colored and charged with the tincture. Once all of the volatile part of the aqua vitae passes and becomes colored, distill this colored volatile part of the aqua vitae in a glass vessel. [The alcohol] will pass white and will be useable three more times. The dye will remain in the bottom, which you should not allow to dry too much, but just moderately. Then you will have the very best tincture or lake for painting from an abundance of flowers and plants.

The "aqua vitae" he refers to is simply a distilled alcohol such as grappa. The important point here is that it is a potent solution of ethanol and water; a well-known modern equivalent would be vodka. The chemical apparatus he describes is about as simple as it got for alchemists. It has three parts; the first is a base consisting of (in this case) a urinal—an inexpensive and convenient glass container with a wide mouth. The second piece is what Neri calls a "cappello"; it is a special glass cap featuring a long tubular snout leading from the top, angled slightly downward. When the cap is affixed to the base with the materials inside and gently heated, vapor will condense in the cap and run down the snout for collection in the third piece, a "receiver" vessel. 

The material he uses to seal the pieces together was called "lute," a mixture of mud, cloth fibers, egg and some other materials that stick to the glass and withstand the heat of the fire. Its only purpose was to keep the glassware sealed until the procedure was complete. [4] 

In the mid nineteenth century, Mary Merrifield made an extensive survey of Italian manuscripts with recipes for artists. She included this comment about Neri's home town:
Florentine lake must have had considerable reputation in Venice, since Leandro Bassano contracted to employ it in his picture of the 'Combat of the Angles,' painted for the church of S. Giorgio Maggiore at Venice in 1597. [5]
Today, this painting is known as 'The Miracle of the immobility of Santa Lucia' and is shown at the top of this post.

[1] L'Arte Vetraria, Neri 1612.
[2] Discorso, Neri 1598-1600.
[3] Neri uses the word "lacca," the equivalent of "lacha" in other manuscripts. For a specific reference to Neri in this regard, see Merrifield 1849, v. 1, p. clxxxi.
[4] A word to the wise: high proof alcohol in a confined glass container near an open flame is a good way to cause a minor explosion and a fireball featuring glass shrapnel.
[5] Merrifield 1849, v.1, p. clxxxiii. She references Cicogna  1824–1858, v. 4, p. 349 for this information. 
* This post first appeared here on 14 Oct 2014.