Lake of Flowers

'The Miracle of the Immobility of Santa Lucia'

Leandro Bassano, using Florentine lakes.

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

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

A Way to Extract the Lake [3] and Color for Painting, from Orange Blossoms, Red Poppies, Blue Irises, Ordinary Violets, Red Violets, Carnations, Red Roses, Borage Flowers, Day Lilies, Irises, and From Flowers of Any Desired Color and the Greens of the Mallow, the Pimpernel and All the Plants. 

Take whichever flower you want, of any color you want, or even a [green] plant. If it will rub green from a leaf onto white paper staining it with color, then it will be good. The plants and flowers that do not show this effect are no-good. Put ordinary aqua vitae into a glass urinal, with a cappello [alembic cap] for its cover, making sure the said crystallo cap is as wide as possible. 

Into this cap, pack the leaves [or petals] of any flower or plant from which you want to release and extract the tincture. Now lute the mouth joint of the cap. Fit a receiver to its snout and lute that joint. Give it a moderated fire so that the volatile part [alcohol] of the aqua vitae rises into the alembic, and falls down into its volume upon the petals of the flowers, extracting the tincture. 

In time, drops will run down the snout of the cap into the receiver, colored and charged with the tincture. Once all of the volatile part of the aqua vitae passes and becomes colored, distill this colored volatile part of the aqua vitae in a glass vessel. [The alcohol] will pass white and will be useable three more times. The dye will remain in the bottom, which you should not allow to dry too much, but just moderately. Then you will have the very best tincture or lake for painting from an abundance of flowers and plants.

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

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

In the mid nineteenth century, Mary Merrifield made an extensive survey of Italian manuscripts with recipes for artists. She included this comment about Neri's home town:

Florentine lake must have had considerable reputation in Venice, since Leandro Bassano contracted to employ it in his picture of the 'Combat of the Angles,' painted for the church of S. Giorgio Maggiore at Venice in 1597. [5]

Today, this painting is known as 'The Miracle of the immobility of Santa Lucia' and is shown at the top of this post.

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

* This post first appeared here on 14 Oct 2014.

Witch's Brew of Glass

Glass pumpkin evocative of chalcedony glass

Courtesy of  Smithsonian Museum store.

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.

Galileo and Glass

Portrait of Galileo Galilei, 1636 (detail),
by Justus Sustermans (1597-1681).

Galileo Galilei lived almost simultaneously with glassmaker and alchemist Antonio Neri. Both were employed by the Medici royal court in Tuscany and both spent considerable time in Florence and Pisa. In Neri's case, possibly also in the Venito and Rome. No direct contact is known to have occurred between the glassmaker and the astronomer, but their paths did cross many times, orbiting like two celestial bodies in the cosmos - albeit one with a bit more gravitas than the other. 

As a youth, Galileo was taught at the Cestello monastery by court mathematician Ostilio Ricci. This was around 1580 when Galileo was sixteen, and Neri was a four year old toddler, living only a block away and attending the Cestello church with his family. Neri's father and grandfather had just been granted citizen status, already well known for their medical prowess, and his father served on the board of the artist's guild based at Cestello. Galileo would go on to become good personal friends with Prince Don Antonio de' Medici, Neri's sponsor. Later, the astronomer would have telescope tubes made by Jacopo Ligozzi, a regular at the Casino di San Marco, where Neri worked as an alchemist and took his first steps into the craft of glassmaking. As Galileo started to experiment with lenses, Neri was leaving Italy for Antwerp and would be absent for seven years. Meanwhile Galileo landed a job at the Florentine court as mathematics tutor to Grand Duke Ferdinando's son, Cosimo II. 

Both Galileo and Neri worked hard for their achievements. In the hindsight of history, innovations are often romanticized into shining moments of inspiration, forgetting the painstaking effort and dogged persistence required to bring those ideas to fruition. For his telescopes, Galileo encountered tremendous difficulty both in the production of suitable glass and in grinding that glass into usable lenses. His celestial observations included sunspots, lunar craters and the planet Jupiter with its moons, which he named "Medicea Sideria" after his Medici benefactors. As these revelations became known, there was a clamor of orders for telescopes from princes throughout Europe and Galileo struggled to keep up. He maintained a circle of trusted craftsmen on Murano in Venice, and elsewhere, but still, the majority of output was unusable.

Initially, he had reasonable success grinding and polishing broken pieces of mirrors. In early 1610, Galileo held a demonstration in Pisa for his former pupil, Grand Duke Cosimo II. A short time later, the grand duke ordered that a special batch of glass be made for Galileo by Niccolò Sisti, for whom Antonio Neri had worked just a few years earlier. At the time, Neri himself was still in Antwerp and would not return until the following year.

Neri returned to Tuscany and wrote his book on glassmaking,  L'Arte Vetraria, but then turned his attention to other pursuits. This, just as Galileo's quest for high quality glass to make his lenses took off in earnest. Neri’s final manuscript places him in Pisa working on alchemical recipes. There was no more optimal moment for the two men to meet; both were working in Pisa, both knew Niccolò Sisti, Neri had just published his book and the astronomer was becoming desperate for clear flawless glass. If such a meeting ever occurred, it has not been recorded, and shortly thereafter, in 1614, Neri died of an unspecified illness.

On 20 December of that same year, four days before Christmas, Tommaso Caccini, Neri's childhood next-door neighbor, delivered a scathing denouncement of Galileo from the pulpit of Santa Maria Novella church. While the sermon earned Caccini a reprimand, and was an embarrassment to his family, it did also serve as a start to Galileo's troubles with the inquisition.

While Antonio Neri may have never encountered the astronomer, shortly after the time of the priest’s death, the astronomer acquired Neri's book on glassmaking. One copy was sent to Rome, to Federico Cesi, founder of the Accademia dei Lincei, a scientific society to which Galileo belonged, and another copy was saved for the astronomer's personal library. Galileo continued his quest for flawless glass and in his correspondence he takes on the same obsession with purity of ingredients that Neri exhibits throughout his book.  

* This post first appeared here in a slightly different form on 18 Novenber 2013.

San Giovanni

"Florence - Church of San Giovanni, the Baptistry",

Photo: Giacomo Brogi (1822-1881).

The San Giovanni Baptistery stands in the heart of Florence, directly in front of the city's most famous structure, Santa Maria del Fiore Cathedral, also known as The Duomo. The church and its dome are so large that they dwarf the baptistery by comparison. Nevertheless, a simple look inside its cavernous, octagonal space easily shatters this illusion. In Antonio Neri's time, this place was a civic hub; a space where masons and tailors rubbed shoulders with nobles and princes. One of the oldest structures in the region, it was also one of most cherished, clad in polychrome marble, with imposing bronze doors intricately sculpted by masters. Michelangelo dubbed them "the gates of heaven." It was here, in this ancient basilica that the future of Tuscany could be seen plainly, in the eyes of its youth. New generations of Florentines were welcomed into the world by their neighbors, anointed and christened, as they had been for centuries. The current structure dates to the eleventh century, but it replaces octagonal baptisteries built on the same spot as early as the fourth century, originally surrounded by a cemetery.

Glass Mosaic ceiling of San Giovanni
(Click to enlarge)

Antonio Neri was baptized here, as were all his brothers and sisters, his parents, some grandparents and quite possibly some much earlier relatives. His sponsor, Prince Don Antonio and his Medici ancestors were also given rights at San Giovanni, in the same octagonal marble bath at its center. The unusual font was a sister to the one still standing in the identically named baptistery in Pisa. Along each side, there was a dry-well. By standing in it, a priest could perform the ceremony and avoid jostling by the crowd. Legend tells that one of the stations showed the repair made after poet Dante Alighieri took an axe to a well in order to free a child who had become entangled and was at risk to drown. The font was replaced later in the same year of Antonio Neri’s birth, 1576, on orders of the Grand Duke, in preparation for a royal baptism.

The ancient mosaic tile floor, although repaired many times, still shows its original signs of the zodiac and other early Christian iconography. As a newborn infant, tightly wrapped in swaddling, Antonio Neri would have been carried across that floor, busy with families and children, and then gently handed to the priest, perhaps by his father, already a famous physician. Joining them would be his grandfather the barber surgeon, his other grandfather the lawyer to Michelangelo, his godparents, other family, friends and perhaps a wet nurse. His mother stayed at home with her close friends to recuperate from the ordeal of birth, and to prepare for a neighborhood celebration. Even in the dead of winter, if Antonio Neri's eyes were open, the sparkling glass mosaics covering the entire domed ceiling of San Giovanni could not have failed to catch the wandering eyes of this future glassmaker.

*This post first appeared here in a slightly different form on 11 Nov 2013.

Neri and The Inquisition

Insignia of the Inquisition, 1574.

The mandate of the Catholic Church's inquisition was to stamp out heresy. Although empowered to impose sanctions that included torture and execution, such extreme measures were not imposed casually. Nevertheless, the Holy Office of the Inquisition  was not an organization with which to trifle. In 1600, just over a decade before Antonio Neri's glassmaking book was printed, former Dominican friar Giordano Bruno was convicted of heresy and burned at the stake in Rome's Campo de' Fiori market, albeit after nearly a decade of confinement and numerous opportunities to recant. Shortly before that, the inquisition ordered Neapolitan polymath Giambattista della Porta to disband his group of scientific investigators and to cease all publication without special written permission from the Church, an order with which he readily complied. Famous French essayist Michel de Montaigne complained of having books confiscated upon entering Rome, although in Florence he was welcomed with open arms by Francesco de' Medici at the Casino di San Marco, where Antonio Neri would later work.

There was special attention paid to books, because they carried the potential to 'corrupt' large numbers of people over a wide geographic area. In the Church's view, heresy was considered a disease of the mind, the devil's work. Books were seen to be a potential source to spread the infection, especially books from the Protestant quarters of Europe, but also from the 'misguided' notions of early scientific investigators.

The last page of Neri’s L'Arte Vetraria [The Art of Glassmaking] is devoted to the official permissions that were necessary to print and sell the book. Here we read that Pie[t]ro Niccolini, Vicar of Florence (a man destined to become the archbishop) ordered Canon Filippo del Migliore of the Florentine archdiocese to review the manuscript. Upon doing so, he found nothing that "contrasts with Christian conscience." Next, it was passed to the Holy Office of the Inquisition, where the head inquisitor of Florence, Fra Cornelio Priatoni from Manza, assigned that the manuscript be reviewed by Agostino Vigiani, Regent of Servants. Final approval came from Florentine Senator Niccolò dell’ Antella.

Within a few years, Cornelio Priatoni would  be embroiled in the investigation of Galileo. In fact, the reviewers of Neri's glass book reads like a cast of characters from the initial investigation of the famous astronomer. The Galileo case would also include Ferdinando Ximenes, the brother of Antonio Neri's good friend Emmanuel. Ferdinando was prior of Santa Maria Novella where the inquisition was based. In fact, Emmanuel's uncle, after whom he was named, also worked in the Holy Office of the Inquisition in Florence and would later give testimony in the Galileo affair.

Writing that could be perceived to defy the Church's teaching was a serious concern for authors in Italy, even those under the protection of the liberal Medici family. Although not overtly heretical, Neri's other manuscripts could have easily fallen into this category. Thankfully for our alchemist and glassmaker, upon reading Neri's book, Vigiani stated "I have not found anything repugnant to the Christian conscience and good customs, but [a book] full of things and natural secrets, no less useful than curious." 

This post originally appeared here in a slightly different form on 13 November 2013.

Solid Water

Rock crystal cup , around 1550,
 Museo degli Argenti, Palazzo Pitti, Florence
(click to enlarge)

In the ancient world, certain natural materials commanded a premium and rock crystal was among the most coveted. Large completely transparent crystals of quartz were found in caves and glacial moraines and craftsmen managed to work them into exquisite cups, vessels and ceremonial objects. By the time the Renaissance arrived, the demand for rock crystal drove much of the innovation in glassmaking. Indeed, clear glass was very much sought after and thought of as an artificially produced form of rock crystal.

A standard line in the historical narrative tells that the ancient Greeks believed that rock crystal was a form of solidified water, the word “krystallos” meaning ice. Enough written material survives from the likes of Herodotus, Pliny, Seneca and Saint Jerome to know for certain that one version or another of this idea has been around for a few thousand years. It is a line that usually gets attention for all the wrong reasons; when stated so glibly, it does not throw any light on ancient culture or our connection to it and worse, it plays into the fiction that we are somehow very much more astute than our relatives of 150 generations ago, that our progenitors were quaintly uninformed. 

Instead, think of “solidified water” as part of a working model of the world. It was consistent with the prevailing conception of nature in the same way that, for modern physicists, eleven-dimensional string theory serves; it seems to be correct, to the best of our knowledge, but the chances are good that there is more to the story yet to figure out. Like string theory, solid water is not a concept that would have a strong bearing on the daily lives of most people. For specialized artisans, it did make good sense; to thinking of rock crystal in this way would be a reminder that if treated too roughly, the material would shatter into pieces as if it were ice.

In the fifteenth century, the Venetian island of Murano became the center of the universe for glassmakers, and it stayed that way for the next four centuries. Of all the many forms that glass can take, the one that made Murano most famous was cristallo; named after the mineral it so closely imitates. The genius of cristallo was in bringing together diverse techniques and ingredients to form a product that was clear like water, yet could be worked thinner and in more complex designs than was possible with carved rock crystal.

 The hallmark of cristallo was the specific use of Levantine soda ash and white quartz river stones (tarso) as opposed to sand and it became the pinnacle of the glassmaker’s art. For the first time, artisans combine best practices with premium raw material sources, the extra purification steps, the careful avoidance of iron contamination, the hot glass washing process, the clean burning hardwood fire and the manganese color correction. In Venetian furnaces, even the clay for the crucibles was a special product imported from Constantinople, which did not contaminate the melt.

In 1450 the Christian world was dealt a severe blow by the Byzantine Empire’s fall to the Ottomans and with it went the Venetian’s major trading partners. That same year, the Murano glassmaker Angelo Barovier is given credit for the development of cristallo. He was the man responsible for bringing together the ultimate refinements that elevated glass to a new level of perfection and created a national product for Venice when they sorely needed it. These techniques and materials were all available and utilized by glassmakers individually at least fifty years earlier, but not together in a single product. Barovier had attended lectures by noted alchemist Paola de Pergola, at the School of Rialto. This indicates that he was thinking along the lines of a chemist in putting together a repeatable regimen for an exceptionally clear, bright, workable product. Barovier’s innovation would become a tradition that was carried on by countless glassmakers and ultimately by our Florentine priest Neri more than a century and a half later.

In seventeenth century Florence, Grand Duke Cosimo I de' Medici negotiated for Venetian masters to teach and practice their coveted techniques in Tuscany. Royal architect and polymath Bernardo Buontalenti was credited with the development of an artificial rock crystal, Tuscany’s own version of cristallo. It is an open question whether we see his hand in Neri’s recipe number seventy-six in which actual precious rock crystal is crushed and used as raw material for glass. In any case, Buontalenti’s continued presence at the Casino must have been an influential experience for his former pupil Don Antonio de' Medici, Neri’s sponsor. Our glassmaking priest was impressed enough with this technique to use rock crystal as the basis for his artificial gems. In turn, Neri’s chapter on artificial gems received the most attention, by far, of any other single subject in his groundbreaking book on glassmaking, L’Arte Vetraria. His work on this subject took on a life of its own and was the subject of plagiarism and unattributed derivative works well into the nineteenth century. An argument can be made that his lead glass based gems fueled the revolution pioneered by English glassmaker George Ravenscroft in what has become the current pinnacle of clear glass: lead crystal.

Black is Beautiful

Black glass cameo vase, c. 1900
Thomas Webb.

Antonio Neri was a technical adept, a student of alchemical history and a glassmaker extraordinaire. He was also a gear in the Medici innovation machine. The glass recipes he developed were likely put to work in the glass shops sponsored by the ruling family in Florence, Pisa and elsewhere. Making advances in technology gave the region a competitive advantage; encouraging the arts cemented a reputation for creativity that endures to this day throughout Tuscany.

Black is one color that has given glassmakers difficulty ever since the material's invention over four thousand years ago. It is easily approximated for large, heavy objects, but to achieve a true solid black in blown vessels, or thin layers is a challenge even for current technology.

Obsidian is a naturally occurring volcanic glass that was prized in antiquity, most often occurring in black or very dark brown. In prehistoric times, it was coveted for cutting tools and arrowheads. As technology advanced, it was ground and polished for mirrors. Later, obsidian became popular in ornamental objects ranging from dinner plates to jewelry. The production of obsidian, gemstones and other natural materials through artificial means was a quest that kept glassmakers busy.

In many ways, making black glass shows the other side of challenges in making colorless crystal; instead of a formulation that will transmit virtually all the light falling on it, the aim is to produce a glass that will absorb virtually all illumination. In his book, L' Arte Vetraria, Neri presents three recipes for "velvet black" glass (# 51-53), and three recipes for black enamel (#100-102).

His first black glass is made with the discarded broken pieces of "glass of many colors." To this, he adds 'zaffer,' a cobalt ore used to produce deep dark blue, and manganese, which produces a magenta color. He advises that it will be good for bead making cane and other work. For his second black glass, he starts with high quality frit to which he adds lead and tin oxides. This forms an opaque, white lead crystal, which he tints with calcined "steel" (probably bronze) and pulverized iron flake. He claims that after twelve hours "the glass will be a most beautiful velvety black." Neri's ultimate black glass is his simplest. He starts with his 'rocchetta' frit, and adds the dried, pulverized dregs left in red wine casks, advising us to go slowly since it froths up. He allows it to cook on the fire for four full days, and finally "washes" the glass by flinging a ladle-full at a time into clean cold water. He then re-melts it; "You will have a black fit for any job and more marvelous than all the other blacks of which I have written."

* This post first appeared here on 8 November 2013.