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, October 30, 2020

Witches Brew of Glass

 

Glass pumpkin evocative of chalcedony glass
In honor of Halloween, we will take a detailed look at chalcedony glass; this is one of, if not the most colorful types of glass ever made. In the seventeenth century, it was extremely dangerous for glassmakers and artists, containing a veritable “witch’s brew” of toxic materials. In his 1612 book, L’Arte Vetraria, glassmaker Antonio Neri presents three recipes of which he is clearly very proud. Each of the three is attended by a complex list of ingredients. He describes the end result this way:
It will be adorned with so many graceful and beautiful areas of undulations, and enhanced with the play of diverse, lively, flaming colors, that truly it will seem nature cannot attain so great a height or grand a prize. [1]
In the same passage, Neri explains the importance of purifying each ingredient and eliminating all contamination. In so doing, he provides a fascinating insight into the thinking of an alchemist. He writes:
There is no doubt that in this art, when the ingredients are well prepared, they permeate the glass with dazzling lively colors. Impurities will ordinarily impede the entry of the tinctures into the glass, and prevent their intimate unification. However, when you open the colors of the metals well, and separate them from their impurities and sediment, their beauty will always by far surpass those that are common and ordinarily made in the furnace. [2]
To Neri’s mind, the metals used as pigments must undergo a process of “opening.” Once this was done, each metal’s characteristic color or “tincture” was free to permeate the glass, provided it was free of impurities. Today we might say that by reducing each metal into an extremely fine powder, the individual atoms more easily disperse in the glass. Neri’s “opening” process usually involved dissolving a pure metal in an acid and then slowly evaporating the liquid, resulting in a fine powder. Most color arises because, once in the glass,  the metal atoms block some parts of the spectrum, but not others. The result is that each metal gives rise to its own hue and only because it is dispersed in the oxygen rich environment of the glass matrix. 

 The striking point here is how the alchemist’s model was a perfectly adequate description for the times, in the same way that the atomic model works for us. Unfortunately, there was less awareness of the negative health consequences in some of these preparations. The evaporation of powerful acids could (and can) certainly cause acute respiratory and tissue irritation. However there were far more insidious dangers lurking in Neri’s chalcedony recipes.
Ribbed vessel, chalcedony glass, 17th century, 
 Museo del Monastero di Santa Giulia, Brescia.

In his first prescription, he dissolves silver, mercury, cobalt, manganese, copper and iron. [3] Some of these have been prepared with sulfur which also ends up in the mix. He evaporates it to a powder and adds it to well seasoned, good quality clear glass along with pulverized chimney soot. He notes “When you stir [the molten glass] thoroughly it gives off a definite blue smoke.” Specifically hazardous in this recipe is the formation of mercury fumes, which are extremely toxic to breathe. 

He advises that in the furnace the glass appears “as red as fire,” but that “master craftsman always pinches off the glass for the job with nippers, and reheats it, in order to make waves, undulations and interplays of the most beautiful colors.” The reheating process is known to modern glassmakers as “striking,” a maneuver that brings out surprising color in some glass formulations. He suggests that this chalcedony can be used to form drinking glasses to more shapely cups, saltshakers, flower vases and similar vessels.

In his second and more sophisticated preparation Neri dissolves the materials in groups, in six separate flasks, only then combining them. He also adds new materials: lead, zinc, “blue painters enamel,” antimony and red varnish. The final recipe for chalcedony introduces new purification procedures and increases the number of separate flasks to nine. Additional ingredients include metal sulfides, ultramarine, tin, arsenic (read: death's calling card) and crimson paint. 

It is tempting to dismiss a few of these ingredients, like red varnish, or pulverized chimney soot; organic materials that would readily decompose in the heat of the furnace. However, Neri is known to have been a careful experimenter and these additions may well have had an effect on the melt, even if not in terms of color. Of the third recipe, which Neri developed in Antwerp, he wrote: 
Many Portuguese gentlemen in the practice of appraising jewels said that nature could do no better. This was the most beautiful chalcedony that I have ever made in my life. While it may be quite laborious and take a long time to produce, the result is fit for a king. I presented His Excellency, the Prince of Orange, with two vessels of this chalcedony, which delighted him greatly. [4]

[1] Neri 1612, p. 34.
[2] Ibid.
[3] Manganese and cobalt were unknown as distinct metals, but were used in their oxide forms, mined as minerals.
[4] Neri 1612, p. 48. The prince of orange was Philip William.
* This post first appeared here on 31 Oct 2014.

Wednesday, October 28, 2020

A Salamander in the Furnace

 

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

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

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

Monday, October 26, 2020

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.

Friday, October 23, 2020

Arminia Vivarini

 

Nef Ewer, Late 16th century, Murano Italy.
Courtesy Milwaukee Art Museum
On the afternoon of Friday, 22 March 1521, The Venetian Senate - then called the ‘Pregadi’ - reconvened after lunch. Senator Marino Sanuto (the Younger) recorded in his now famous diary that among the afternoon business was the granting of a ten year exclusive license to Arminia, the daughter of painter ‘Alvise da Muran’ (Luigi Vivarini). She was granted this privilege to produce the ornamental glass galley ships she had recently devised. [1,2] Once called 'Navicella' (little ships) these ewers, probably most used to serve wine, are now known as ‘nefs’. A pour spout was situated at the ship's bow, and often a handle astern. These objects soon became iconic symbols of the island-nation’s long dominance in trade, and regularly appeared on sideboards and elaborate dinner table settings, not only in the lagoon, but in Florence, Rome and far beyond.


In their Objects of Virtue: Art in Renaissance Italy, Syson and Thornton write,
“It was not only the use of coloured canes in complex patterns embedded into clear glass that typified Venetian glass from the 1520s, but also the manipulation of cristallo into ever more fantastic forms. Novelties were first displayed at the Ascension Day Fair, which, like visits to the glasshouses in Murano itself, was firmly on the tourist map by about 1500. The Venetian diarist Marino Sanuto mentions the work displayed at three booths at the fair in 1525, those of Barovier, Serena and Ballarin workshops ‘among other things, a galley and a very beautiful ship were to be seen.’”
Syson and Thornton continue, “Leandro Alberti singled out just this kind of glass in his famous description of the marvels of Murano in his Description of All Italy of 1550: ‘I saw there (among other things made of glass) a scaled-down model of a galley, one braccia long and with all its rigging and equipment, so perfectly in scale that it seemed impossible to model such things accurately in such a medium.” [3]


Scholar and science investigator, Georgius Agricola, described a vessel in the form of a ship in his De re metallica published in Basel in 1556,
“The glass-makers make diverse things, such as goblets, cups [...] and ships, all of which excellent and wonderful works I have seen when I spent two whole years in Venice some time ago. Especially at the time of the Feast of the Ascension they were on sale at M[u]rano, where are located the most celebrated glass-works. These I saw on other occasions, and when, for a certain reason, I visited Andrea Naugerio in his house which he had there, and conversed with him and Francisco Asulano.” [4]


Arminia Vivarini’s father was a painter of some renown, but her family is also among the earliest recorded glassmakers on Murano. Her third-great grandfather, named Vivarino, arrived from Padua, just ahead of the plague in 1346. [5] The family seems to have been involved in the craft on the island from then on. She clearly had access to a furnace, perhaps one owned by an uncle or a cousin. In any event, she exemplified the qualities of the very best glass artisans throughout history: a clear design sense coupled with technical expertise and the opportunity to put them both into practice.


Her very existence also forces us to more closely examine the well worn narrative that hot-shops were exclusively male domains, from which women were strictly excluded. In such a highly competitive arena, it is perfectly reasonable that a family would promote its best talent, regardless of gender. In many ways, we owe homage to Vivarini for her success with this style of novelty glass object; it started the genre that continues in popularity today, five centuries later, with works of art prized by collectors and in museums around the world. [6]


[1] Arminia  (Armenia, Ermonia) Vivarini (1490-1569). See Luigi Zecchin: Vetro e Vetrai di Murano, 3 vols. (Venezia: Arsenale, 1987-9) v.3, p. 194.
[2] Marino Sanudo: I diarii di Marino Sanuto (1466-1536)  v.30. Eds., F. Stefani, G. Berchet, N. Barozzi (Venezia: Fratelli Visentini, 1891) col. 45. Also see Zecchin 1987-9, v.2, p.276.
[3] Luke Syson, Dora Thornton: Objects of Virtue: Art in Renaissance Italy (Los Angeles: J. Paul Getty Museum, 2001), p. 197.
[4]  Georgius Agricola (Georg Bauer): De Re Metallica: Tr. from the 1st Latin Ed. of 1556… trns: Herbert Hoover, Lou Henry Hoover. (Princeton: Mining Magazine, 1912), p. 592 (Book XII.)
[5] op. Cit. Zecchin 1987-9, v.3, p194-5.
[6] Thanks to Sophie Small‏ @sophieesmall for inspiring the subject of this post.

Wednesday, October 21, 2020

Anna Agnew, Champion Glassblower

 

Anna J. Agnew,
Chicago Tribune, 9 March 1902, p. 43
In the spring of 1902, newspapers around the United States reported that eighteen-year-old Anna Agnew, of Norwood Pennsylvania had been proclaimed a “champion glass blower.” Stories in New York, Pennsylvania, Alabama, Virginia, Florida, Chicago and Arizona described how she was able to blow several thousand pieces of medical glassware per day. Speaking to the rigors of her profession, she stated that in the past two years her lungs had become stronger and that she had “increased in weight from 110 to 130 pounds since taking up men’s work.” When asked if she was a member of the glass workers’ union, she replied “No, as the hateful men would not take women in as active members.” [1]

Agnew worked for the glass house of the H. K. Mulford Company, a pioneering pharmaceutical outfit that grew out of the first apothecary in Philadelphia, founded in 1823. The facility was located just outside the city in idyllic Glenolden. The owners had made a strategic decision to attract a female labor force for their line of torch-made scientific glassware and sterile containers. The women “have a delicacy of touch and a deftness which make them specially fitted for expertness.” [2] Their superintendent said, “I’ve been in this business from boyhood up, and I know what I am talking about when I say that no men can turn out such good work as these girls do. [Male] glass blowers would be astonished if they looked in on this factory. The girls are infinitely more careful and painstaking than men have ever thought of being, and they are achieving results never before known in the trade.” [3]

In the not-so-distant history of American glass work, women played a strong but understated and now all but forgotten role. Anna Agnew fabricated antitoxin bulbs, goose-necks, and did ‘fancy’ glass work besides. Her female co-workers were experts at producing capillary tubes, hermetically sealed ampules and homeopathic vials. But the appreciation of female glass workers was not by any means confined to the Mulford company. Elsewhere, women around the country were specifically recruited as glass workers in other fields. From the tiny Moore Pushpin (thumb-tack) company [4] to the burgeoning incandescent light bulb industry. As Agnew and her co-workers honed their skills in the east, the Houston Electrical Supply Company in Texas advertised for “Lady Glass Blowers” experienced with incandescent lamps. Even earlier, In the 1890’s Edison’s General Electric company was running help wanted ads for “Female Glass Tubulators and Stem Makers” for his incandescent light bulb factory in Harrison, New Jersey. [5] There, women composed the vast majority of blowers making glass bases and envelopes for light bulbs. By 1918 General Electric maintained 36 lamp factories around the world, and the women at the Harrison plant met to discuss forming a union of their own. [6] Still later women became vital to the manufacture of vacuum tubes for electronics, and by the 1940’s they were working side by side with their male counterparts at the hot-glass furnaces of the Libbey glass company in Toledo, Ohio. [7]

The appreciation of female glass workers by industry in the late 1800s did not materialize out of thin air; far from it. In fact, it is not an exaggeration to say that every man, woman and child in America had heard of, read about, or seen a lady glassblower ply her craft in person. They were a widely popular attraction at county fairs, circus sideshows and dime museums. In an era when traveling performers were the premier form of entertainment in the country, glass blowers working over a torch were especially popular with women and children. Audience members could expect to walk away with a small glass toy; a model ship, an animal or a flower made entirely of glass. To see a woman making such objects was icing on the cake, a fact not lost on show managers and promoters. By the last decade of the 19th century, there were troupes entirely composed of “lady glass blowers” traveling the country, headlining their own exhibitions.

Anna Agnew was the daughter of a Philadelphia sewing machine salesman. After her stint with Mulford, she married trolley car conductor Harry Stewart and as far as can be determined, retired from the fire-arts to raise a family. She died at age 74 in Philadelphia in 1957. Other women continued their career in glass throughout their lives. There is a strong and proud tradition of women glass workers in the arts and industry that carries over from Europe and runs like a golden thread right through the entire history of the United States since its earliest days.




[1] “Girl Champion Glassblower” Chicago Tribune: Chicago, Illinois, 9 March 1902, p. 43.
[2] “Glass-Blower Girls” The Buffalo Enquirer: Buffalo, New York, 29 July 1904, p. 5.
[3] Day, Mary Edith, “Girls Who Blow Glass” Reading Times: Reading, Pennsylvania, 14 May 1902, p. 3.
[4] “Help Wanted” The Philadelphia Enquirer: Philadelphia, Pennsylvania, p. 40.
[5] “Female Help Wanted” The Boston Globe: Boston, Massachusetts, p. 9.
[6] “Have Mass Meeting of Lamp Works Employees” The Fort Wayne Sentinel: Fort Wayne, Indiana,  31 December, 1918, p. 3.
[7] Rosellen Callahan, "Lady Glassblowers Wend Their Way Into 'For Men Only' Trade", Fort Lauderdale News: Fort Lauderdale, Florida, 5 August, 1943, p. 6.

Monday, October 19, 2020

Thomas Edison's Lady Glassblower

 

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 on the grounds 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, and apparently made his decision to go with all girls. 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 information conduit on the pumps.

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.

Friday, October 16, 2020

Fire, Brimstone and Glass

 

The Alchemical Symbol for Sulfur
Bright yellow elemental sulfur or “brimstone” as it was often called, occupied a central place in the cabinets of seventeenth century alchemists. Antonio Neri used it in many of his preparations and specifically in pigments for glass. When sulfur is heated with thin sheets or shavings of metal, foul smelling chemical reactions can take place that reduce the metal to a powdered compound and some of these turn out to be effective glass colorants. Neri’s 1612 book, L’Arte Vetraria, offers a variety of recipes, which specifically prepare iron and copper using sulfur to form pigments. In reality, the resultant chemicals were mixtures of oxides and sulfur compounds. Since these also chemically interact with each other in the glass melt, many different effects are possible. Modern glass artists sometimes specifically use both oxide and sulfide pigmented glass side by side in the same piece; a striking effect can be the spontaneous formation of a third color along the boundary. As Neri says in the closing line of his 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.[1]
Keep in mind that the thinking of alchemist Neri was that the sulfur acted upon the metal, but did not necessarily combine with it. From his point of view, the exposure resulted in the metal’s infusion with new properties. The Aristotelian conception of the world was that everything under the sun contained various amounts of four elemental essences: air, water, fire and earth. Sulfur was seen to be dominated by the latter two, ‘fire’ because it burned easily and ‘earth’ because it occurs as a solid.

In the sixteenth century, a Swiss physician named Paracelsus developed an extension of the four-element system. After his death, his writings enjoyed a new popularity among chemical experimenters in the period that Neri came of age. Since his teenage years, the work of Paracelsus was a strong influence on both Neri and separately on his benefactor, Florentine prince Don Antonio de’ Medici. According to Paracelsus, sulfur was one of a triad of “principles” consisting of salt, sulfur and mercury. These three had philosophical as well as physical interpretations attached to them. Besides other applications, like in medicine, the three physical materials figured prominently in efforts to transmute one metal into another. 

In fact, sulfur in particular played a starring role in a very convincing demonstration that purported to turn iron into copper. Mining operations often utilized water to clean or separate ore from tailings. Other times, water was used to keep dust down, or simply flowed naturally through underground springs. When sulfur-bearing earth is exposed to air and moisture, the result can be the formation of dilute sulfuric acid. This “vitriol” was an irritant to the eyes and skin, and very unpopular with the miners. However, in at least one location, it seemed to have a miraculous property. When this “vitriolated water” flowed out of the mine, it seemed to transform bits of iron into copper. [2]

Chemically, copper had already been dissolved in the acid, forming a copper sulfate solution. But sulfuric acid shows a preference for iron. When the copper solution flowed over iron tools, it took up the iron and dropped the copper, depositing it in a thin layer. The effect appeared to be a transmutation of iron into copper. Further testing and scrutiny confirmed that pure iron, when exposed to the mine fluids resulted in real copper. Neri for one was well aware that the vitriolated water might have arrived containing copper, as he explains in his manuscript Discorso. [3] But apparently, it did not occur to him that the water leaving the scene might have contained the iron. If he had made the connection, the observation would have advanced the understanding of both ion-exchange chemistry and the principal of conservation of matter; these were two ideas that would not be explored seriously for another hundred years.

Well into the eighteenth century, the mine at Smolnik, (now in Slovakia), was a highly touted tourist destination for chemical experimenters. [4] For some, it was considered among the strongest evidence that transmutation could and did take place in the natural world. I like this demonstration so much because it works the same way as a parlor trick; while we are so intently focused on the metal changing before our eyes, Mother Nature quietly slips the copper in with one hand and takes the iron away with the other, no one the wiser.


[1] Neri 1612, p.114.
[2] See this post for a more detailed description  http://www.conciatore.org/2014/01/turning-iron-into-copper.html
[3] Grazzini 2102.
[4] The effect had previously been described Georgius Agricola, in book 5 [9] of Nature Fossilium. See edition, transl. from the first Latin edition of 1546 by Mark Chance Bandy, Jean A. Bandy (New York: Mineralogical Society of America, 1955), p. 188.
*This post first appeared here on 7 November 2014.

Wednesday, October 14, 2020

Crocus Martis

The many different alchemical symbols used to denote crocus martis.
In order to understand the seventeenth century glass recipes of Antonio Neri and for that matter, any alchemical recipes, it is first necessary to have a grasp of the chemical repertoire; no degree in chemistry required. The ingredients referenced by Neri were not especially exotic, but over the intervening four centuries since he wrote, the common names of materials have changed considerably. In the current lexicon, we name materials by their chemical formulas, so iron oxide names its two constituent elements, iron and oxygen. But in the seventeenth century, the periodic table of elements was a concept yet to be invented; hence "crocus Martis." Martis refers to Mars, the Roman god of war, the red planet, and the ancient alchemical name for iron. The origins of crocus are lost, but it may refer to the similar looking spice saffron, (crocus sativus) which has been highly valued since antiquity. Poetically, 'saffron of Mars' alludes to the orange-red color of rust. 

A first encounter with the technical recipes of sixteenth and seventeenth century alchemy can be confusing, frustrating and more than a little disorienting. There is no shortage of records, letters, manuscripts and recipe books that have been preserved from that period, however, the challenge lays in making sense of them in a way that relates to our current view of the world. It is understandable that alchemical materials and compounds had unfamiliar names; but even larger difficulties arise with the realization that any given name might describe several different chemicals, and in fact, there may be several different interchangeable synonyms/symbols for any given name. As it happens, there were good reasons for this state of affairs. The challenge of deciphering alchemy is not insurmountable. Taking the time to understand really opens up a window onto a strange and wonderful landscape of history. 

Antonio Neri considered himself an alchemist first and glassmaker second. His purely alchemical works are somewhat cryptic, but in the glass book he bends over backwards to be accessible to novices. Because of this crossover, his work can help us to navigate details in both areas that might otherwise go without explanation. His writings broadly divide into two categories: one intended for generally curious readers and another intended only for those familiar with the arcane coded language of alchemy. We have examples of both styles by Neri and all written within the period of about fifteen years at the beginning of the seventeenth century. As a result, we can use his works intended for a general audience to decode some of his more arcane passages elsewhere. With the glass recipes, his careful explanations lead us to gain considerable confidence in his technical abilities. In the introduction to his famous book on glassmaking, L'Arte Vetraria, he wrote, "I have described every last detail clearly and distinctly in this work, I am sure that if you do not purposely foul up, it will be impossible to fail, after having acquired experience and practice." Even in Neri's more obscure works, he earned the respect of later chemists; in 1870, in the journal Nature, George Rodwell, the first science master of Marlborough College, pronouncing him a "sensible chemist." Rodwell went on to note that Neri had used "no less than thirty-five different names, and twenty-two symbols" to denote a single material, the metal mercury. 

In still other writings, it becomes clear that Neri was deeply concerned that some alchemical operations were inappropriate for general consumption and were better kept secret among true practitioners of the art. In particular, he worried that if the transmutation of base metals into gold and silver were practiced widely, the result would be a collapse of the economy and would ultimately plunge civilization into disarray.

We will start with his glass book, where his materials and methods are detailed with special consideration for those not familiar with the art. Then perhaps we can build on that and make sense of his more esoteric material.

In L'Arte Vetraria, Neri gives four different methods to make crocus Martis. He explains: 
Crocus Martis is nothing other that a refinement and calcination of iron. A means by which its pigment, that in glass is a deep rutty red, is opened and imparted to the glass. It not only manifests itself but makes all the other metallic colors as well, which ordinarily hide and are dead in the glass, dance in resplendent apparition. Since this is the way to make the hidden metallic colors appear, I have put down four ways to make it.
The term calcination means only 'to roast' in a hot oven. It derives from the ancient practice of cooking seashells into powdered quicklime, which is a prime ingredient of cement; now called calcium oxide.  In his first method for crocus Martis, Neri mixes iron filings with sulfur and then heats the mixture in the furnace for a long period. We can guess that the result is a mix of iron oxide and iron sulfide. These are the constituents of a popular red pigment of the same name (Crocus Martis) used in pottery glazes. In the second method, he takes the iron and sulfur mixture and sprinkles it with vinegar and leaves it in the sun for many days. The third method uses aqua fortis (nitric acid) for better effect. In the fourth and final method, Neri uses aqua regis, an even stronger acid. 

In all four cases the predominant result will be for the acids to chemically react with the metal to form iron oxide and sulfide, but alas, chemistry is not that simple; there will be minor concentrations of other compounds depending on the acid used, which may or may not affect the final product. We must consider that vinegar and the other acids in the seventeenth century were significantly different from those products today. They were made by different methods and contained a variety of impurities that would never be found in the current products. As Neri notes, each method produces different effects in the glass and therefore we must conclude that each, to some extent, differs in chemistry as well. Today, we know that iron forms several different oxides, each responsible for different color effects in glass. In a number of green glass recipes Neri uses crocus made with vinegar, yet in chapter 71 he uses it to diminish the green in yellow lead crystal. In chapter 124 he uses crocus made with aqua fortis for red glass. The lesson here is that the name of a material tells us only the basics, how it was made is at least as important if not more so. 

* this post first appeared in a somewhat different form on 15 August 2014. 

Monday, October 12, 2020

Vitriol of Venus

 

Crystals of Copper Sulfate Pentahydrate
(Vitriol of Venus)
Vitriol of Venus was one of the most cherished items in Antonio Neri’s chemical library. In his book, L'Arte Vetraria, he describes its effect in glass this way:
To your great contentment, you will be astonished at what you see. I do not know of anybody else who has tried it this way and I Priest Antonio Neri trying it found it most marvelous, as said above, and it is of my own invention. [1]
To be clear, Neri is claiming a novel preparation technique for a chemical substance that was known since antiquity. I think it is quite reasonable to say that a particular personality trait led him down this path of discovery; his almost maniacal drive for purification. For a seventeenth century alchemist, it is a trait that served him well. Where other practitioners were content to use contaminated or substitute ingredients in their formulations, Neri always goes the extra mile in verifying his ingredients and using any extra filtering steps that might be warranted, no matter how time consuming. More than anything else this is what led him to such success in glass formulation, the assurance of exceptionally clear product and bright colors.

He is so proud of his creation that he spreads the description of his method over four full chapters of the book, going into a level of meticulous detail that is extreme, even for Neri. Rest assured, dear readers, that I have taken the liberty of distilling said description down to a more manageable form for your reading pleasure. Nevertheless, our priest-alchemist clearly puts great stock in this preparation, going so far as to drop hints that this material has uses that go far beyond glassmaking: "Many things could be said here, which are omitted as not being pertinent to the art of glassmaking, which perhaps upon another occasion you will be able to judge." [2]

Before starting, he gives some general advice:
You should make the sulfurs, vitriols, ammoniac salts, and similar materials slowly, over a low fire, so they are well prepared and well opened, because a violent fire will cause great damage to them.[3]
To begin, Neri cuts thin copper sheet into small pieces half the size of a small coin. filling a crucible, he layers the copper pieces with common sulfur (known as brimstone).  He cements the vessel shut with a lid and then buries it in the hot coals of a drafted furnace for two hours.

The dark purple contents are then ground and sifted through a fine screen, mixed with six ounces of pulverized sulfur per pound and then heated in a round terracotta pan, which is sitting in the hot coals. When the sulfur starts to burn, he stirs the mixture, rolling it into balls with an iron hook so it does not stick to the pan, continuing until it stops smoking. He removes the mixture from the heat, grinds it finely, adds more sulfur and repeats the entire process three times.

Neri grinds the resulting reddish tawny colored material into powder, putting a pound of it into a large glass vessel containing six pounds of clean water and gently evaporate away a third of the water. The liquid is carefully poured off and saved. The residual solids are dried and recycled in the process. Now more solids are allowed to settle out of the "beautiful blue" liquid over a two-day period and then the liquid is filtered through a felt cone.

He heats the liquid again, this time evaporating two thirds and then puts the remaining third into glazed terracotta pans, and leaves them in a cold damp place overnight. "You will find the vitriol of copper has formed into crystalline points that mimic true oriental emeralds." The crystals are removed, dried and the liquid is further evaporated in order to obtain more crystals. To the chemist, this material is copper sulfate pentahydrate [4]; today it is sold inexpensively as a fungicide for swimming pools. One reason it was so valuable to alchemists is that when gently heated or added to water this chemical forms a sulfuric acid solution. 
This is the true flaming azure blue [tincture], with which marvelous things are made. It is most potent, and as sharp as anything known in nature today, as can easily be perceived from its odor.
However important this was in other areas of alchemy, those applications do not have any particular relevance to the blue-green tint it imparts to glass, which he does make use of throughout the book. The full recipe was so long that he continued it several times and finished as the final chapter of L'Arte Vetraria. Here are the closing words to 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.[5]
[1] Neri 1612, ch. 31.
[2] Ibid, ch. 133.
[3] Ibid, ch. 37.
[4] CuSO4•5H2O
[5] Ibid, ch 133.
* This post first appeared here on 29 Aug 2014.

Friday, October 9, 2020

Casino di San Marco

 

The Casino di San Marco, Florence
Location of Antonio Neri's first glassmaking job
In 1612, Antonio Neri wrote the first book entirely devoted to making glass from raw materials. It was called L’Arte Vetraria, or in English, 'The Art of Glassmaking'. When Neri put pen to paper for his book, he had already been making glass for over a decade. He had the opportunity to learn his craft from some of the experts in the field. At the beginning, his first known experience in glassmaking was at the laboratory palace of Don Antonio de’ Medici, a prince from the ruling family of Tuscany. 

The Palace was called the Casino di San Marco. “Casino”, we might innocently guess indicated some kind of gambling hall, which it was not.  Instead, "Casino" was Italian parlance for a palace that was informally organized like a small country house with the living quarters on the ground floor. It was built by Don Antonio’s father, the former Grand Duke, as a place where Nature’s secrets would be discovered and new inventions would be made. Neri worked at the Casino for a couple of years before moving to Pisa and then to Antwerp, all the while making glass. He returned to Florence to publish his book, in which he thanked Don Antonio for his long patronage. 

Don Antonio's Casino was as much a grand concept as it was a physical space. Completed to his father’s specifications in 1574, it evolved into a prince's palace par excellence. Within its walls, grand dinners were held, productions were staged and poetry was read. In 1605 Michelangelo Buonarroti the younger staged a play there titled "The Christmas of Hercules." In its chambers, music was performed, philosophy debated and diplomacy conducted. In its laboratories, alchemy was nurtured, and glass was formulated. It was a sort of grand royal conservatory, melding together art, letters, drama, music and science. From its courtyard, hunters set forth into the Tuscan hills in search of unicorns, and within its workshops, artisans explored the territory of new materials and natural secrets.

The Royal Foundry, as it was also called, became a place of pride for Grand Duke Ferdinando. It was a place that visiting dignitaries specifically asked to see and tour. Behind the doors of the Casino di San Marco, Antonio Neri and his associates worked their magic. This is probably where he first learned the secrets of Venetian style glass composition and undoubtedly much more. He assisted the prince in his research, formulated herbal remedies and helped in the production of luxury gifts for visiting dignitaries.


This was the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there. At that time, the task of scheduling furnace-work fell to the outstanding Mr. Niccolò Landi, my close friend and a man of rare talent in enamel work at the oil lamp. I made many pots of chalcedony in the furnace there. I never deviated from the method stated above, I always prepared the materials well and it always came out beautifully in all my proofs.[1] 

[1] L'Arte VetrariaAntonio Neri 1612, p. 41.
* This post first appeared here in a shorter form on 12 August 2012.

Wednesday, October 7, 2020

Caterine Sforza

 

Caterina Sforza, by Lorenzo di Credi
(now in the Museum of Forlì.)
We remember Antonio Neri mostly for his book on glassmaking, L'Arte Vetraria. However, he thought about himself a bit differently; he considered himself first and foremost an alchemist. This interest can be traced to at least two generations before him; his father, Neri Neri, was an acclaimed physician – in fact, the personal physician to Grand Duke of Tuscany, Ferdinando I de’ Medici. Antonio's grandfather, Jacopo Neri, was a barber-surgeon. Both of these professions required an extensive knowledge of herbal distillation and other techniques which are shared by alchemists.

Antonio's benefactor, Don Antonio de' Medici, also followed a family passion for the chemical arts, in his case, traceable through an unbroken chain, to a female alchemist, his great-great-grandmother, Caterina Sforza, (c.1463–1509). After her death, over four hundred of her formulas were passed down to her son, Giovanni dalle Bande Nere, then to his son Grand Duke Cosimo I de' Medici, Grand Duke Francesco I, and finally to Don Antonio. 

Caterina was the illegitimate daughter of the Duke of Milan, Galeazzo Maria Sforza, but was still educated at court, and apparently 'apprenticed' apothecary Ludovico Albertini. At age fifteen, she was married to a nephew of Pope Sixtus. The pope granted her title of Countess of Forlì and Imola. After her territory was later taken and her husband murdered (by a faction of their own people), she escaped prison and retook the two cities. In 1495, when her second husband was assassinated, she launched a campaign which gutted the families of the murderers. Her third husband was Giovanni de' Medici, and their son, named after his father would become a brilliant military strategist, like his mother. His own son, Cosimo, would later become the first "Grand Duke" of Tuscany. 

Her chemical recipes were transcribed in 1525 by a captain in her son's army, Count Lucantonio Cuppano da Montefalco, and ultimately published as a book in 1893 (Pasolini). Included are an assortment of formulas which range from cosmetics, to medical remedies, poisons and alchemical concoctions.
Researcher Jacqueline Spicer writes:
Lost among the romanticized military conquests is a thorough account [of] the project that occupied several years of her life—the manuscript of her alchemical and medical experiments and recipes titled Gli Experimenti de la Ex.ma S.r Caterina da Furlj Matre de lo inllux.mo S.r Giouanni de Medici, or Gli Experimenti. The text is an early example of what would later become the popular medical genre of "Books of Secrets", but is so early that it does not appear in most modern writing on such books. Furthermore, Gli Experimenti is unusual because it was written by a woman in an otherwise male dominated genre, and unique in that we know a great deal about the life of its author.[1]

Among the alchemical entries are "to convert pewter into silver of the finest quality and of standard alloy," a method "for giving to bars of brass a fine golden color" and another for "for multiplying silver." Also, there are ways described  to "make iron hard," "to dissolve pearls" and "to dissolve all metals." In the medicinal category, we find "for infirm lungs, an ointment is to be made of the blood of a hen, a duck, a pig, a goose, mixed with fresh butter and white wax." This was to be applied to the chest with a fox's skin.
Sandro Botticelli, Primavera (1498)
(detail - rightmost of the three graces)

Caterina Sforza was painted many times and often depicted as the Virgin Mary, a typical trope for the nobility at the time. She may have been immortalized  by Sandro Botticelli as the rightmost of the three graces in his Primavera and as the main subject in The Birth of Venus.[2] Reportedly, she was the subject of ballads and sonnets, although most have been lost. She is a topic of discussion in Niccolò Machiavelli's famous treatise The Prince

In the end, our alchemist's territories were confiscated by yet another pope, Alexander VI, and her story does not end well. She was captured, raped and imprisoned. Alexander justified her incarceration, in the Vatican's Sant'Angelo Castle, by claiming she tried to poison him. She survived the ordeal, but after release entered the convent of the Murate nuns in Florence, and died, in 1509, at the age of forty-seven. She was buried at the convent, in the same city where her future great-great-grandson, Don Antonio, along with Antonio Neri, would perform their own alchemical experiments and help usher in the age of  modern science.

[1]https://sites.eca.ed.ac.uk/renaissancecosmetics/cosmetics-recipes/caterina-sforzas-experimenti/ also see  http://edinburgh.academia.edu/JacquelineSpicer.
[2] Another possibility for the model of Venus was Simonetta Vespucci.
*This post first appeared here on 27 January 2014.