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

Wednesday, February 28, 2018

A Glassmaker's Birthday

Relief portrait of Antonio Neri,
artist unknown, La Specola Museum,
Florence.
Alchemist, Glassmaker, and Priest Antonio Neri was born in Florence, Italy on 29 February 1576. From his baptismal record, we know the exact time of birth: "three hours and 25 minutes past sunset." In terms of current timekeeping conventions, sunset occurred on that particular Thursday at about 6:15 pm (local time) so the big event happened at 9:40 pm.

It might seem a bit odd to have such accurate records -- almost as if an astronomical event were being recorded. Actually, that is exactly what was being done; astrology of the sixteenth century drew a strong correspondence between 'macroscopic' events in the heavens and more earthly matters. To have an exact time of birth was seen as a way to gain greater insights into the events of ones personal life and to plan in a way that was more in harmony with the natural order of things.

Of all the days to be born, 29 February was considered among the least auspicious. A dire Northern Italian folk proverb states "An bisesti, o la mama o 'l bambi" predicting that, born on this day, a child or its mother was fated to die by year's end. Indeed, the Italian word naming the day, bisestile, had become a synonym for misfortune or calamity and is still the case for the French cognate bissêtre. Whatever stock the family put into ancient superstitions, happily this prophecy did not come true for Dianora or her fourth child Antonio.

Although his was a February birth, it was perhaps not as deep into winter as one might assume. Due to a discrepancy in the Julian calendar, which was in force then, the Spring equinox of Neri's birth year happened much earlier in the calendar than today, around 10 March, in fact. 

Infant mortality was not uncommon and for a child to die unbaptized only magnified a family's trauma. Church theologians had debated since the fourth century on the fate of the souls of such children. Most Catholic families baptized infants as soon as humanly possible, in Antonio's case the very next morning. Births occurring within Florence were officially registered at a central baptistery, San Giovanni, the ancient octagonal basilica standing directly in front of Florence's main Cathedral. 

The full baptistery record, in translation, for Antonio Neri reads:
Thursday, 1 March 1575:  Antonio Lodovico was born to Mr. Neri di Jacopo and Dianora di Francesco Parenti, residents of San Pier Maggiore parish. The time of birth was 29 February, at 3 hours 25 minutes past sunset. The godparents are Francesco di Girolamo Lenzoni and Ginevra di Federigo Sassetti.
The year is recorded as 1575 because in those days, Florentines celebrated the New Year on 25 March. Today we consider January, February and March to be part of the new year. 

Antonio joined a growing family that already contained siblings Lessandra, Jacopo and Francesco, and later would number ten children.  His father was thirty-six year-old Neri di Jacopo Neri, (Neri Neri to his friends) and his mother was twenty-one year-old Dianora Parenti. Neri Neri was a prominent doctor and later was appointed to be the personal physician to Grand Duke Ferdinando. Dianora was the daughter of Francesco Parenti, Michelangelo's lawyer. 



Tradition dictated that births were celebrated with a house party open to friends and neighbors. Thirty-four year-old Francesco Lenzoni, Antonio's godfather, would certainly have done his best to attend. His family included Florentine senators and Francesco himself would later become Tuscan ambassador to Spain. Godmother Ginevra Sassetti, in her late fifties, was also from a prominent family. Her nephew Filippo would send plant specimens back from India to be inspected by Neri Neri and their mutual friend Baccio Valori who would become director of the Laurentian Library in Florence.

Antonio Neri, would go on to learn the finer points of alchemy and glassmaking, developing new formulas and techniques that would be applied throughout Europe. In 1612, he published the world's first book entirely devoted to formulating glass, L'Arte Vetraria. It seems especially appropriate that we pause and raise a toast (in glass, of course) to his accomplishment and to the end of February, looking forward to warmer days ahead. B
uon compleanno Antonio!

Monday, February 26, 2018

Washing Molten Glass

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

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

* This post first appeared here on 9 May 2014.

Friday, February 23, 2018

Primordial Matter

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

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

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

** This post first appeared here 30 April 2014.

Wednesday, February 21, 2018

Cross Pollination

The art of stonework,
from MS Ferguson 67, f. 7r, (1598-1600)
Antonio Neri.
Throughout the Renaissance, Florence, Italy was famous for its artistic output. Names like Donatello, Michelangelo and Giambologna graced the tongues of patrons across Europe. But the secret to the city’s fantastic creativity did not rest solely on individual superstars. The ruling Medici family had found a way to harness the talents of myriad lesser known artisans and use the fruits of their creative labor as a powerful political tool. 

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

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

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

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

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

*This post first appeared here on 19 March 2014.

Monday, February 19, 2018

Eyes of a Lynx

The seal of the Accademia dei Lincei.
In the spring of 1612, Florentine priest Antonio Neri published his book on glassmaking. L'Arte Vetraria was the first printed book devoted to the formulation of glass from raw materials, but unfortunately for him it did not exactly take the world by storm, at least not at first. Sales were such that a number of copies still exist from the initial printing; they remain in pristine condition, never bound. 

Initially, the book received scant attention, but it was noticed. In fact, within a couple of years word had reached Rome, where Prince Federico Cesi, the founder of a scientific society, asked a Pisan member of his group to obtain a copy. That other member would go on to become one of the most recognized scientists in history. Meanwhile, L'Arte Vetraria gained prestige and readers, slowly but steadily.  By the end of the century, Neri’s book would be translated into English, Latin, German, French and then back into English from the French. It became the bible of glassmakers throughout Europe. 

In 1614, the year of Antonio Neri's death, naturalist Prince Federico Cesi wrote to his good friend Galileo. He complained of the difficulties in getting material from the Roman libraries, urging the astronomer to send him a copy of Antonio Neri's book.
The poor management of these libraries in Rome makes me feel continually thirsty for good books that come to light, which I can use for my study of compositions. They are scarcely giving me the titles, and after a long wait, only a tenth of what I asked. […] now I hear that printed in Florence is L'Arte Vetraria by Priest Antonio Neri, and I think there is some good in it. Please, your lordship, send me a copy, and believe me that I will gladly give them trouble.
 Shortly after, having received the book the prince wrote,
I thank your lordship for the book on glass, which I find very rich in experiments and beautiful artistry.
In 1603, Cesi founded the Accademia dei Lincei (Society of the Lynxes), an early scientific society whose members (with eyes as sharp as a lynx's) eventually included both Galileo Galilei and Giambattista della Porta.[1] Within a few months of Neri's death, his book was already on its way to making history.

[1] In classical Greek mythology Lynceus was the grandson of Perseus, and had preternaturally keen eyesight. See Apollodorus, Bibliotheke I, viii, 2 & ix, 16; III, x, 3 & ix, 2.



* This post first appeared here in a shorter form on 1 August 2013.

Friday, February 16, 2018

The Glassmaker's Salamander

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

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

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

Wednesday, February 14, 2018

Rosichiero Glass

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

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


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


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

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

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

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

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

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

Monday, February 12, 2018

Laughing in the Ferm

Allain Manesson Mallet  1719,
"Der Mont. – Lune"
In Chapter 5 of L'Arte Vetraria, Antonio Neri shows how to extract salt for glass from fern plants in an evocative recipe. Fern was and still is widely abundant in Tuscany. It presented a ready source material for glassmakers of the region. Neri directs that harvesting of the plants be done in the spring:
Cut this herb from the ground when it is green, between the end of the month of May and mid June. The moon should be waxing and close to its opposition with the sun, because at this point the plant is in its perfection and gives a lot of salt, more than it would at other times and of better nature, strength and whiteness.
At first, it is tempting to dismiss this lunar influence as the product of a fertile imagination, but let us take a closer look. Even today, grandmothers throughout Italy remember the advice to pick vegetables from the garden and bring them into the kitchen at a half-moon. Can nona be completely off-track? The fact is that tidal forces of the moon do subtly affect plants, fish and animals in ways that can be measured. A closer look at Neri’s advice reveals reasoning that is hard to dismiss as mere astrological superstition. When the moon is waxing, tides rise and so do water tables. According to folklore, this is when sap rises from the roots of plants into stems and leaves. Sap carries the dissolved mineral salts required for glass. Neri also stipulates that harvesting should take place during lunar opposition. When the moon is 'opposed' to the sun, it is on the opposite side of the earth from the sun. In opposition, the moon is near full and rises as the sun sets. Plants see more light at night, leading to increased photosynthesis and growth.

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

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

Since the middle ages, fern glass became part of everyday life in northern Europe. It was familiar enough to find its way into literary verse on matters of the heart. There is a nice reference to fern glass by Geoffrey Chaucer, in The Squires Tale:
But notwithstanding, some said that it was
Wondrous to make fern-ashes into glass,
Since glass is nothing like the ash of fern;
But since long since of this thing men did learn,
Chaucer, in turn, borrowed this reference from an epic twenty-two thousand line French poem from the late thirteenth century, when the technique of making glass from ferns was already ancient.

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

Friday, February 9, 2018

Dyed in the Grain

Dyeing wool cloth, from "Des Proprietez des Choses"
Bartholomaeus Anglicus, 1482
British Library Royal MS 15.E.iii, folio 269
In his book on glassmaking, L'Arte Vetraria, Antonio Neri presents a number of recipes for paint pigments used to decorate finished glassware. One recipe (#119) is for crimson red, from kermes [kur-meez], prepared by a method of his own invention, which he developed while working in Pisa in 1602–1603.

Since antiquity, throughout Europe and the Near East, kermes was a highly valued red colorant because it formed a pigment that resisted sunlight, humidity and temperature. Kermes red can be found in prehistoric cave paintings, Egyptian scrolls and the robes of cardinals and kings. Words in many languages used to describe bright red, "crimson" and "carmine" among them, are derived from the name "kermes." The pigment is produced from the bodies and eggs of a small type of insect that feeds on the sap of evergreen oak trees throughout the Mediterranean region. In the spring, the female kermes insects and their eggs were harvested. The small eggs surrounding the edges of the insect body resemble kernels of grain, hence the expression "dyed in the grain." For medicinal purposes, kermes pastes were used to disinfect wounds and served as an effective contraceptive. 

To extract the color, Neri starts with a flask of "the very best grappa," which is a potent kind of liquor made by distilling the skins, seeds, stems and pulp of grapes, leftover from wine making. To this, he adds a pound of alum and one ounce of the dried kermes insects, ground finely and sifted. He agitates the mixture, at which point the grappa will "color beautifully" and then lets it sit. After four days, he adds four ounces of alum dissolved in water and pours the mixture into a stocking that has been sewn into the shape of a cone. The stocking hold most of the color, while letting the grappa pass through. 

Alum is another material used since antiquity. It was widely available in Neri's time as a mined mineral, which could actually be several different chemical species with similar properties. Today, chemists know it as a "flocculant"; it neutralizes the electrical charge of finely suspended particles in a liquid, allowing them to stick together and fall to the bottom. This is the secret to Neri's method, although he was not thinking in modern chemical terms, he did know that the alum precipitated the pigment from the liquid allowing it to be collected and dried.

Finally, he scoops the pigment onto pieces of linen stretched over newly fired terracotta tiles and lets it dry. He advises:
Do not spread it too thickly, because then it will not dry quickly. When there is too much moisture it will mildew, and make an ugly color. When a tile has absorbed a lot of moisture, take another new tile. In this manner, it will dry more quickly. When it is dry, remove the coating from the linens. This will be a good lake for painters, as I have made many times in Pisa. Take note that if the color is too strong you should use more roche alum and if it is too weak use less alum so that the color is according to your taste, and desire.
Through the fifteenth century, kermes was among the most sought after pigments, but by Antonio Neri's lifetime, its use was declining in favor of a new insect-based red called cochineal that Portuguese traders brought back from Mexico. Cochineal bugs inhabit the prickly pear cactus. They give a more intense color and eventually replaced kermes throughout Europe.

*This post first appeared here on 26 February 2014.

Wednesday, February 7, 2018

The Duke's Mouthwash

Ferdinando de’ Medici (1549-1609),
Scipione Pulzone (1544 - 1598), Private collection.
Antonio Neri's father, Neri Neri, was royal physician to the family of Grand Duke Ferdinando de' Medici. As such, he regularly interacted with other members of court, ranging from the archbishop of Florence, to his colleagues in medicine, including the royal apothecary (speziale), Stefano Rosselli. Rosselli shared more than a professional relationship with Neri Neri. They both admired the work of an ancient Greek physician named Dioscorides; Rosselli was something of an authority on his methods. In addition, he ran the 'Speziale al Giglio' shop, once owned by Tommaso del Giglio, who's chapel Neri Neri took over at Cestello church. Rosselli's son, Francesco, and Neri Neri were among the four chosen to revise and update the famed Ricettario Fiorentino,[1] the official reference for medicinal cures in Tuscany. 

On 21 September 1589, Rosselli started to compile his own book of recipes to pass down to his two sons, Francesco and Vincenzo, who would go on to continue the pharmacy.[2] The book begins with a poison remedy credited to none other than Cosimo de' Medici. Recipe no. 9 is the grand duke’s antispasmodic oil, presented by Niccolò Sisti, with whom Antonio Neri would later work at the glass house in Pisa. No. 20 is the duke's oil for deafness, also presented by Sisti. No. 41 is a poison antidote revealed to Francesco de' Medici by the Archduke of Austria. It was tested on a prisoner at the Bargello prison, a "volunteer" who was intentionally poisoned as part of the experiment, then revived with the antidote in the presence of Stefano Rosselli and Baccio Baldini, the long time physician to Cosimo I. Supposedly, the prisoner's reward for surviving was early release.

Recipe No. 30 carries perhaps a bit less risk; it is titled "Acqua da gengie di messer Nerj Nerj" (Mouth wash of Neri Neri):
Take a quarter of a bushel of mastic buds,a quarter of a bushel of myrtle buds, a quarter of a bushel of red roses, three ounces of alum, a half ounce of salt and a quarter ounce of hard rose honey. Mash the herbs with a mortar and pestle and put them in nine pounds of Greek wine for twenty-four hours, then boil in a bain-marie and reduce to two-thirds. In this, we bathe the gums: it makes them dry and firm.
MasticPistacia lentiscus. Native to the Mediterranean, its resin used for millennia to settle upset stomachs.
MyrtleMyrtus communis. An Aromatic herb used by the ancients, effective treatment for sinusitis.
Alum: Used by the ancients as a treatment for canker sores.
Rose HoneyMiele rosato. Honey infused with rose petals, an astringent still used to sooth children’s teething pains. It is produced both as a solid and a liquid. 
Greek Wine: Vino Greco. Italian wine made in the style of sweet Greek wines. In 1673, English botanist John Ray describes it as being made from grapes grown on the slopes of Mount Vesuvius.

The date that Stefano Rosselli started his book of secrets is interesting because it is the same day that Neri Neri, with the grand duke's two other physicians, Cini and Da Barga, were busy making medicinal wine based on Dioscorides' ancient recipes. Perhaps they all met that day at Rosselli's shop, for his advice. 

[1] Neri, Benadù, Rosselli, Galletti 1597.
[2] Rosselli 1996; an Italian transcription and French translation of Rosselli's recipes, with a very entertaining introduction.

* This post first appeared here on 4 November 2013 in a shorter form.

Monday, February 5, 2018

Isaac Hollandus

J. Hollandus,
Chymische Schriften
(Vienna: 1773)
In early 1603, Glassmaker Antonio Neri traveled from Italy to Flanders, to visit his friend Emmanuel Ximenes. Neri would stay for seven years and in that time he worked on a number of glass related projects including the manufacture of artificial gems using lead crystal glass. An enduring mystery is that in his glass book L'Arte Vetraria, he gives credit to alchemist Isaac Hollandus for a "new chemical method never before used," yet no such recipe for artificial gems has ever been found in the writings of Hollandus.

Neri’s host Emmanuel Ximenes owned several titles by this somewhat obscure figure. Historians conjecture that there were actually two alchemists in the Hollandus family, Isaac and Johannes Isaac. Their relationship is not clear, although they are often assumed to be father and son. We know little about them; some authors date them as early as the fourteenth century. However, a preponderance of evidence point to about the time Neri lived. In his glass book, in the fifth part devoted to artificial gems, Neri writes:

Above all is this wonderful invention. A new way practiced by me, with the doctrine taken from Isaac Hollandus, in which paste jewels of so much grace, beauty and perfection are made, that they seem nearly impossible to describe and hard to believe.

In the 1679 German edition of L'Arte Vetraria, Johannes Kunckel implies that Isaac was dead before Neri came to Antwerp, writing "This is the manner to imitate precious stones, of Isaac Hollandus, (namely, from his posthumous writings) that I [Neri] learned in Flanders" (emphasis added). Yet, coinciding with Neri's visit, playwright Ben Jonson who had just returned to London from the war in Flanders, referenced the pair in his satirical work The Alchemist (1610). There he implies that the elder Hollandus was then dead but survived by "living Isaac." In 1644, the famous Flemish chemist Van Helmont identified Isaac Hollandus as a recent contemporary. In a 1716 treatise, Kunckel paid Hollandus a great compliment and at the same time took a swipe at Helmont saying "and the incomparable Hollandus had more of the fire-art in his little finger as Helmont in his whole body." In another reference, Sir Francis Bacon mentions Hollandus as "by far the greater part of the crowd of chemists."

One Hollandus title in Ximenes' Antwerp library was Opera Mineralia, first published in 1600. The subject of this volume is the philosopher's stone and its production. While there are no artificial gem recipes here per se, there are some intriguing connections between artificial gems and the philosopher's stone, both philosophical and practical. It was thought that the colors of metallic based glass pigments were an indication that the metals were "opened" and became susceptible to alchemical transmutation. Of special interest was the deep red ruby color made by adding gold to the glass melt. In the introduction to a 1797 French translation of Neri's book, artificial ruby or "vitrified gold," is equated to the bible's Electrum of Ezekiel —a red glow seen by the prophet in a vision.

By the mid-eighteenth century, Isaac Hollandus was lauded in industrial arts books as a genius of artificial gems. He may well have been, but the evidence does not support it. All of the specific recipes attributed to Hollandus seem to lead back to Neri's L'Arte Vetraria or its translations. A case can be made that Hollandus' reputation for artificial gems stems from a 1697 plagiarized version of Neri's book. A volume published in France by Haudicquer Blancourt that gives no credit to the priest. Blancourt used Christopher Merrett's English edition as his base and added to the recipes with his own embellishments. The chapter on artificial gems still lauds Hollandus, but its length was now doubled from the seventeen original recipes to thirty-five. The size of this one section jumped from thirteen to nearly two hundred pages, an increase in page-count larger than Neri's entire book. In 1699, Blancourt's version was then translated back into English, again without reference to Neri. There is no doubt that these two editions, with their expanded chapters on paste gems exerted a strong influence on later craftsmen. They may also be the source of the credit given to Hollandus' for paste gems in the eighteenth and nineteenth centuries.

A number of intriguing questions remain unanswered. Chief among them is the nature of Neri’s association with the Dutch alchemist(s). Was Hollandus or his son alive in the first decade of the seventeenth century and did Neri meet with either of them in person? We can only guess. The Hollandus men are notable, if not enigmatic, characters in the transition from alchemy to modern chemistry. Historians would very much like to know them better. Nevertheless, there can be no doubt of the strong impact Hollandus made on Neri. Isaac holds a singular honor as the one person named in Neri's book to whom he gives specific credit. As research on early modern science has progressed, the importance of communication between practitioners has emerged as a central theme. A meeting of the minds between Neri and Hollandus, if it ever occurred, would rank as a prime example of technology transfer with a definite impact.


For a comprehensive look at Hollandus see: Annelies van Gijsen, "Isaac Hollandus Revisited" in Chymia: science and nature in Medieval and early modern Europe, Miguel Lòpez-Pèrez, Dider Kahn; Mar Rey Bueno, eds., (Newcastle upon TyneUK: Cambridge Scholars, 2010), pp. 310–324.
*This post first appeared here 2 April 2014.

Friday, February 2, 2018

Glass in Early America

Note: This is an abbreviated version of a piece appearing in the Autumn/Winter 2016 issue of the NAGC Bulletin. Many thanks for their permission to share it here. A copy of the complete article is available through inter-library loan from the numerous public and art museum libraries which subscribe to this journal, (including the Rakow Library at The Corning Museum of Glass). The Bulletin can also be obtained directly from its publisher, the National American Glass Club.

Glass: A poem by Henry Schoolcraft


In the final years of the 1700s, a third generation family that was living in New York’s Hudson River Valley welcomed a new son, Henry Rowe Schoolcraft (1793-1864). They welcomed him into a newly formed country, brimming with promise and expectation, the United States of America. His father was the superintendant of a new window glass factory near Albany. The family boasted a long line of military men, but perhaps more importantly, a long line of adaptable, self-motivated, life-long learners and young Henry was no exception.  

With the help of his father and like-minded family friends, Henry parlayed a rural education into private instruction in Latin, a premier collection of scientific books, and a museum quality mineral collection.  In 1809, at the age of 16, he started a hand-written literary magazine called “The Cricket” in which he published short pieces of prose and poetry among a circle of friends. His time at Union College was cut short by the opportunity to manage a glass factory further west on the shores of Seneca Lake, near Geneva, New York.

Along with his father, Henry went on to become one of the most sought after glass factory guru’s in New England. In 1814, he was running the Vermont Glassworks on the shore of Lake Dunmore. He had set up an experimental furnace with Prof. Frederick Hall from the college in nearby Middlebury.  Henry used the facility to research glass composition for a hefty book he was writing on the subject. Managing by day, experimenting by night, he still found time for his literary pursuits. It was here, in the autumn of 1814, that he composed a remarkable poem titled “Glass” in which he compares commonplace personalities of the early 19th century to the vitreous material of which he was so familiar.

Until now the poem has never been published beyond the first few stanzas.  “Glass” runs for 268 lines of rhyming couplets in a lose meter. The handwritten manuscript is archived at the Library of Congress. It begins with an assessment of mankind: [1]




1
Mankind resemble glass; they are, like it,

For use or fashion, show or service fit;

Some bright and fair, some dull and more obscure,

These prized as good, those, estimed poor;
5
To grace a kitchen, or a parlour made,

As use is most consulted, or parade;

But all as various; and eke they are,

As frail, as brittle, and as keen a ware.



Their bases differ, as our chemists say,
10
This made of sand, that fashioned out of clay

Yet shall we, in both compositions find,

Similitude in beauty, use and kind.

To man, tis true some small objections lie

In point of texture and transparency,
15
But though we grant him, in material blind,

Yet lacks he not, transparency of mind

And we no surer faults in each detect

By rays of light, than rays of intellect.



So nice the processes, the art requires,
20
So pure th’ ingredients, so intense the fires,

Where tumours grow, where phthysic’s fitful breath,

Forbodes the public faith, a sudden death.

Felons, freckles, frightful fire warts,

Are all disclosed as clear as limpid quartz.


25
His voice and pen are graced with equal skill,

To lash, report, or advocate a bill.

Speak without nostrums, clear his throat when lost,

But ever loudest, when they shuffle most.

Alike to him, the subject, time or stage,
30
Fierce to discuss, and ready to engage

If finance—there Blaberius is at home

If raising troops, he votes with general glum.

In peace he’s noisy, but if wars involve’

He blasts the foe by one august “Resolve.”
35
Prate, prate, prate, prate! the error of the land,

His voice, by every vulgar breeze is fanned

Nor learn from Witherspoon his course to run,

The simple cause, “to stop when he has done.”

(Read full poem)





NOTES  
(Line numbers are referenced in parenthesis) 

The exact manuscript title as written by Schoolcraft is: GLASS, | A Satire Poem. | Lake Dumnore, 1814.

(4) Estimed: Vernacular loanword from the French, estime; valued.

(7) Eke: also.

(10) “Feet of clay” is an expression referring to a weakness or character flaw. The phrase derives from the interpretation of the dream of Nebuchadnezzar, King of Babylon, by the prophet Daniel as recounted in the “Book of Daniel.” (Daniel 2:31–33, 2:41–43).

(21) Phthisic: a wasting illness of the lungs, such as asthma or tuberculosis; phthisis. Any wasting disease. A person suffering from phthisis.

(23) Felon: a carbuncle or other localized infection of the skin. Fire warts: “The hand that reached farthest down on the shovel is burned forever with calloused fire warts.” William E. Bain, Frisco Folks: Stories and Pictures of the Great Steam Days of the Frisco Road (St. Louis-San Francisco Railway Company) (Denver: Sage Books, 1961), p. 96.

(25) In the ms, “Graced” is struck out and replaced by a word that is smeared and illegible to me.

(27) Nostrum: a medicine, especially one that is not considered effective, prepared by an unqualified person.

(31) Blaberius: possible Latinization for ‘one who blabbers’. Also blaberus: a genus of giant Central American cockroach.

(35) Prate: to talk foolishly or tediously about something.
(37) Witherspoon: John Knox Witherspoon (1723–1794).

Footnotes:
[1] Paul Engle, “Glass, A Poem by Henry Schoolcraft” in Glass Club Bulletin, of The National American Glass Club, No. 230, Autumn/Winter 2016, pp. 5-14.