Friday, May 17, 2019

Glass Discovery Legend

Giovan Maria Butteri,
"The Discovery of Glass"
Studiolo of Francesco I de' Medici
Any self-respecting Roman historian living in the first century could tell you the story that glass was first discovered by Phoenician sailors. They were temporarily grounded at the bay of Haifa, near the Belus River, in the shadow of Mount Carmel, forced ashore by a storm. Needing to eat, they improvised a fire on the beach in order to cook their food. Using natron, a mineral they were carrying as cargo on the ship, they built up a stove. To their amazement, in the heat of the fire, the natron mixed with the beach sand started to melt and liquid glass trickled out.

Actually, starting with Pliny the Elder, the author of most famous version of this story, skepticism abounds about how much of it was true. Nevertheless, if we gently tease apart the loose threads of this yarn we find that it is not without substance. First, there is the location; not just any port in a storm, this region was the site of a thriving glass industry as early as the sixth century BCE, due to the exceptional, pure white sand at the outlet of the Belus river. Archaeologists have excavated ancient glass furnaces at the nearby cities of Tyre and Sidon.

Next, the sodium carbonates in natron do indeed form glass when mixed with fine sand and brought to a high temperature, but this takes strong, concentrated heat, likely more than could be provided by a cook's beach fire. Natron is a hydroscopic mineral – this means it pulls moisture out of the surrounding environment. The water is locked into its solid crystal structure, where it remains until it is released either chemically or through heat. Natron can hold a remarkable amount of water, up to two-thirds of its weight. This is why it was used extensively to preserve mummies in Egypt; it dried out the bodies, quickly preserving them. While the story of the Phoenician sailors deserves a healthy dose of skepticism, it is also easy to see how the decomposition of the natron in the fire, resulting in the release of briny liquor, might be misinterpreted as glass.

In the early 1600s glassmaker and alchemist Antonio Neri published the first printed book of glass recipes, and in his introduction he too recounts the tale. However, in Neri's telling, natron does not make an appearance. Instead, the sailors use 'kali,' a coastal plant that is rich in alkali salts, to fuel their fire. The salts in kali are substantially similar to natron and, according to the story, triggered a similar result. In this period, Kali ash was a well-known ingredient in glass making. Neri used it in his own recipes, so the substitution is not surprising, but in this respect, Neri's version of the story does appear to be unique in the literature. It is interesting to note that Lodovico Domenichi, who was good friends with Neri's grandfather, tells a version of this story in his Italian translation of Pliny's Natural History. Here the sailors use natron, but in the next paragraph, Domenichi describes how local natives later used the plants to make their own glass.

The above depiction of the discovery of glass was painted by Butteri, one of a select group of painters for the Medici court in Florence. The work was commissioned to hang in the secret "studiolo" of Francesco de' Medici, a concealed barrel vaulted room tucked under a staircase in the Palazzo Vecchio in the early 1570's. It was only accessible through secret passages, one leading from Francesco's bed chamber. Another led from the chamber to an unmarked door on the street and a third passage led from the chamber to the secret treasury room once used by his father, Grand Duke Cosimo I. The walls and ceiling were entirely filled with paintings, the lower ones concealing cabinets full of oddities of nature, precious gems, coins, alchemical concoctions, and other treasures. Presumably, the cabinet behind Butteri's "Discovery of glass" would house some of the intricate Venetian glass vessels for which the craftsmen of Murano had become world famous. Shortly before the room was completed, a small number of these glass masters were allowed to teach their secrets in Florence by special arrangement with the Venetian government.

This post first appeared in a shorter form here on 9 October 2013.

Wednesday, May 15, 2019

Alberico Barbini

The island of Murano , circa 1600
attributed to Danckerts
In the early seventeenth century, Antonio Neri began preparing batches of glass for the royal family in Florence, Italy. This was a specialist vocation undertaken by alchemists, which by schooling, Neri was. His job as “conciatore” involved procuring the ingredients, preparing, mixing and melting them and working with the glass artisans, adjusting the consistency and colors for the work being done. It was a position that carried great prestige, and Neri’s book on glassmaking [1] would cement his name in history. 

Shortly before Neri was born, in 1576, the grand duke of Tuscany, Cosimo I de’ Medici, brokered a special deal with the doge of Venice to have master glass artisans come to Florence and teach their secrets. These men were from the island of Murano; the most famous center of glassmaking anywhere. There is only scant evidence that Neri himself traveled to Venice and perhaps only once, but there is no doubt that he benefited greatly from the knowledge of Muranese workers in Florence, Pisa and Antwerp during his lifetime. 

Over the intervening centuries, the title of the glass batcher changed, but the tradition and prestige of glass formulation continued well into the middle of the twentieth century. In fact, even today, among the small glass manufacturers that compose the studio glass movement, the glass batcher is considered to be something of a modern alchemist; keeper of the arcane knowledge of  the chemicals and amounts necessary to produce special colors and adjust properties of the glass.

Now, fast forward four centuries from Neri's Italy; in the early 1920s, a Milanese lawyer named Paolo Venini partnered with a Venetian-born antique dealer friend, Giacomo Cappellin, to start a new glass factory on Murano. [2] Even as recently as this, the glass batcher still held a respected position both within the factory and the community. Through several incarnations over the next half century Venini grew a world-wide reputation for innovative designs, of which color played an important part. They are specifically associated with the fazzoletto (handkerchief) style vase and the incalmo technique of fusing two or more colors of glass seamlessly in a single furnace-blown piece. 

In 1925, Cappellin split from Venini and took many of the craftsmen with him, in 1933 the new business was acquired by Pauly & C. Again, chemical knowledge and the artistry of reproducing ancient colors made a worldwide reputation. [3] As ownerships changed hands like cards in a game of poker, artisans shuffled between factories. It is easy to lose track of the individual glassworker. Even for a period so recent, many records exist only in the heads of the family members still living on the island. 

In 1956 the Stazione Sperimentale del Vetro (Experimental Station for Glass) was started on Murano with the mandate to preserve and promote the technical aspects of Italy’s glassmaking heritage. [4] The new institution was regarded by some traditionalists with great suspicion, but as we will see, others embraced the resource.

I recently sat down with renowned glass artist Emilio Santini, who today carries on a six-centuries-old family tradition in glasswork. [5] Emilio had recently called home, to Murano, which led to his father’s recollection of an uncle, who worked making color for Venini and Pauly. Here Emilio recounts the conversation:
Alberico Barbini was the uncle of my father, Mario Santini and the man in charge of making the glass batch “partie” (Venetian) “partite” (Italian). He was the brother of my grandmother, Delfina Barbini. He was not the only one [in my family] who worked for Venini in the early days but the most respected. At Venini he worked formulating glass after another great batch maker, [Albino] Carrara. 
In the early to mid [twentieth] century the batch maker still held an important position in the factory, not like now, you know, and he kept his formulations quite secret, although this relative of mine, Alberico, was smart enough to use the most modern technology available at that time. 
He was different from other batch makers in that when the Stazione Sperimentale del Vetro opened, he made extensive use of it in reproducing colors. At that time, and even now to an extent, the institution was not seen as good for traditional Murano glassmaking. 
He later moved on to Pauly where he was in charge of reproducing the glass colors that were in use in the seventeenth, eighteenth and nineteenth centuries. First, he assisted in remaking broken or missing pieces in private collections, then later in making reproduction antique stemware at Pauly that was impossible to distinguish from the originals. 
You must realize that all this does not come from documents but from the memory, still very sharp and lucid, of my father.
Addendum: On 7 August 2016, at the age of 96, Mario Santini died, surrounded by his family at his home on Murano.


[1] L’Arte Vetraria, (Neri 1612).
[2] Paolo Venini http://en.wikipedia.org/wiki/Paolo_Venini also see https://www.facebook.com/pages/Venini/198475426829887
[3] Pauly & C. Compagnia Venezia Murano http://en.wikipedia.org/wiki/Pauly_%26_C._%E2%80%93_Compagnia_Venezia_Murano
[4] Stazione Sperimentale del Vetro  http://www.spevetro.it/indexENG.htm
[5] Emilio Santini http://www.cmog.org/bio/emilio-santini
* This post first appeared here on 25 Feb 2015.

Monday, May 13, 2019

Laughing in the Fern

Alain 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 which contain a minimum of sap. 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, May 10, 2019

Alchemy of Plants

Antonio Neri, Tesoro del Mondo, f. 9r.
"Arts Preparatio frugu vel Piantar."
In a 1598 manuscript devoted to "all of alchemy", Antonio Neri singled out four particular practices, each of which he made the subject of a detailed illustration. Each is devoted to a different "art"; preparing animals, stone/minerals, plants and metals. The manuscript was produced over a period of two years starting when he was just twenty-two years old. He began writing shortly after his ordination as priest and the work was completed before he was employed making glass for the royal Medici family in Florence. 

Neri is best known for writing the first printed book of glassmaking recipes, so we might expect to find that subject covered in the early manuscript, but nothing appears aside from a single recipe for artificial ruby which makes use of glass. Indeed, the general conclusion of historians is that his involvement in making glass did not start until 1600 or 1601. Absent of any direct citation of that art, the manuscript does show a familiarity with the kind of individual skills required. Among the things Neri would need to know was the ability to make "glass salt" from certain dried plants. Presently we will look into the third of the illustrations mentioned above, which he titled "The Art of Preparing Fruits or Plants." [1] All of the activities depicted here relate to food and drink, yet they could easily be applied toward other purposes.

While there is scant reference to glass in the text, the pictures are filled with examples of specialized vessels for chemical production and investigation. From these figures we know Neri at least received an exposure to the glassmaking profession earlier. He must have started his training in alchemy as a teenager while still studying for the priesthood. This is not hard to imagine since his father was the chief physician to the grand duke of Tuscany, and would have a strong grounding in alchemical techniques for producing medicines. Indeed, the first sentence of Antonio's 1612 book on glassmaking, L'Arte Vetraria, begins: "I have spent years of my youth laboring around the glassmaking craft, and experimented with many fine and marvelous effects." [2]

At center-left of the illustration at hand, we see a male farmer holding a flail, perhaps going about the business of threshing wheat, which appears in a bale behind him. Figuring prominently above the farmer (upper left) is a large mechanical apparatus that appears to be a gristmill powered by a waterwheel. A conical bag feeds grain or possibly corn from above into the central hole of a horizontal grinding stone supported by a large rectangular box. We can easily imagine that the gears shown on the front of the box control the drive or the gap between the stones. Wheat, of course, was an ancient well established staple. Corn was introduced as a direct result of Columbus' voyage to Cuba and by Neri's time, corn was being widely cultivated throughout southern Europe, northern Africa, and even as far as China.

Returning to the illustration, on the immediate left of the mill is a woman, who we can guess, is fashioning rolls or small loaves of bread from dough made with flour from the mill. Below her, (center right) is a boy using a long paddle to put the balls of dough into a baking oven. In effect, Neri is showing us the full chain of events from harvesting to finished baked goods. 

Further down, another woman works over a large basket of herbs, which appear destined for three large glassware stills to her right. In his book, Neri presents numerous recipes for extracting paint pigments from flowers using similar methods.

At the bottom of the illustration, a third woman stands in a large wooden tub crushing grapes with her bare feet, as grape juice runs into a pan on the right. To her left are three wine barrels standing side-by-side. 

For us, the connection to alchemy might seem tenuous with the possible exception of the distilling stations. For Neri, there was a deep lesson here about the way nature works; in his later manuscript Discorso, he uses the growth of grain as a metaphor for "multiplying" the "seeds" of gold inherent in primordial material left over from the creation of the world. 
This is confirmed by the example of seeds, of which a single grain is capable of producing a hundred or a thousand, as long as you sow them in a commensurate place. Take the further example of fermentation, in which one small part is sufficient to ferment a large mass. Nor is it contradictory to say that the metals do not produce seeds, like herbs and plants, because even though nature by itself has no power to take the seed out of gold, however, aided and encouraged by art, [nature] will do that which it does not do by itself. So that art begins where nature ends, and art will perfect the seed, which in gold is merely begun. [3] 
Given knowledge of how to work in harmony with nature and bring about the right conditions, he was convinced that a small quantity of material could be converted into a large amount of precious metal. The illustration on the art of preparing plants simply showed a different manifestation of the same principle; he is showing how grain multiplies in the fertile earth, it is then transformed through the addition of water and fire into nourishment.

[1] Neri 1598–1600, f. 9r.
[2] Neri 1612, p. ii.
[3] Grazzini 2012, p. 454, (Neri, 1613).
* This post first appeared here in a slightly different form on 10 Sept 2014.

Wednesday, May 8, 2019

Early Modern Lapidaries

Antonio Neri, Tesoro del Mondo, 1598-1600
f. 7v, "Ars Preparatio Lapidum"
In 1598, in his early twenties, before his glassmaking career began, Antonio Neri completed an extraordinary manuscript. Tesoro del Mondo or 'Treasure of the World' was devoted to all aspects of alchemy and was intended for publication, but it never saw a printer's ink. By a minor miracle of providence, the manuscript survives today, in the special collections department of the University of Glasgow Library. The pages include a set of fascinating images, this one (left) among them.   Labeled "The Art of Preparing Stone," the picture shows five men working with various pieces of equipment related to the art. [1]

In the upper-left a lapidary works at a polishing wheel. It turns at low speed, driven by a belt which is powered from below, possibly by a foot pedal. The artisan holds two polishing fixtures against the surface of the disk, while four more stand at the end of the table. Under this workstation is an inscription in Italianate Latin that reads "Accontiare et lustrare pietre praciose" [preparing/dressing and polishing precious stones]. Behind the lapidary are shelves holding finished pieces. They range from small objects that appear to be rings, to cups, vessels and large bowls, presumably all made from stones, gems or minerals. 

Proceeding clockwise to the upper-right side of the image, we arrive at a worker tending a furnace with iron tools. Inside is a crucible sitting in the flames. Below is the firebox, and underneath that is the word "Calcinare" [calcination], which in Neri's parlance refers to the process of breaking down a material into a powder usually through the use of heat. Neri uses this method extensively in his glass formulations; in his book L'Arte Vetraria, [2] almost every colorant discussed is a metal which requires "calcination" before use in the glass melt. In the case of stone, Neri uses the furnace to make the main ingredient of glass. He breaks down quartz stones into powder by repeatedly heating them and then quenching in cold clean water. The rocks fracture into coarse granules which are then ground into a fine powder.

The middle-right of the illustration shows a worker checking on a distilling apparatus. This consists of a small stove and three pieces of glassware.  The "body" holding the raw material to be evaporated or sublimated is capped by a "head" that sports a long snout leading to a "receiver" vessel which collects the finished product.  Stills were useful in producing everything from alcoholic spirits like grappa to acids and reagents. Their specific use in stonework is not clear, possibly in dissolving precious metals from the constituent minerals in stone.

The lower-right portion of the image depicts two men seated at a low bench, each holding specialized tools used to shape "alabaster, marble and porphyry." Finally, in the lower-left we see a specialized mortar and pestle used to grind stone and minerals into a fine powder.

The two benches and the distilling stove all bear a distinctive diamond shaped insignia with a small circle at its center. The two men in the lower portion of the illustration appear to be working on a stone inlay version of this same pattern.  The implication is of an identifying symbol, but a specific affiliation is elusive.

 This technique of creating designs entirely in colorful gems and minerals (pietre dure) is an ancient one revived by the Medici family, specifically by its first three grand dukes.  In the 1560s Cosimo de' Medici employed two such artisans (commessi) in the courtyard of the Palazzo Vecchio. By the 1570s a larger group was working out of Francesco de' Medici's new palace, the Casino di San Marco. In 1588 Ferdinando de' Medici moved them into the Galleria dei Lavori [Gallery of Works] at the Uffizi Palace where they were named the "Opificio delle Pietre Dure." [workshop of hard-stone]  There the organization thrived and refined the art of creating inlaid stonework to the point of producing realistic life-like scenes. Their work graces the most opulent spaces in Florence, including the Chapel of Princes and the interior of Santa Maria del Fiore. The Opificio delle Pietre Dure continues to operate to this day. The organization has been charged with the maintenance and conservation of many of Italy's great works of art. They maintain a worldwide reputation for excellence. [3]

It seems well within the realm of possibility that Neri's illustration indeed depicts an early incarnation of the Opificio. The artisans working in Pietre dure were handling precious materials and as such might not be readily accessible to the general public. The fact that Antonio Neri's father was a prestigious member of the Medici royal court all but ensured his entree to the royal workshops.

[1] Neri 1598-1600, f. 7v.
[2] Neri 1612.
[3] Official website: www.opificiodellepietredure.it/
* This post first appeared here in a slightly different form on 3 Sept 2014.

Monday, May 6, 2019

Glass, Fire and Brimstone

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.

Friday, May 3, 2019

The Dregs of Alchemy

"The struggle of fixed and volatile" 
allegorical illustration from
Splendor solis [detail] 16th C.
To 17th century Italian glassmaker and alchemist Antonio Neri, "Dregs" were otherwise known as terra, gruma, immondita, terrestreità and the evocative sporchezza. It was the "filth" and sediment left in the bottom of vessels after useful material was extracted from a preparation. These often foul-smelling substances were sometimes discarded:
Then filter out the dregs of the vitriol impregnated water; that which is yellowish you should throw away. –L’Arte Vetraria, chap. 38.
Other times, dregs were further refined. A notable example was the potassium rich muck left at the bottom of aged wine barrels. This was Neri's secret ingredient in producing a fine, sparkling cristallo glass. To understand the distinction between the useful and the useless forms of dregs, we must dig deeper into Neri's philosophy.

It might be surprising to some that these lowliest of materials could play an important role in the theory of transmutation—the alchemists' ultimate quest—which was to turn base metals into gold and silver. The idea was that a natural evolutionary process occurred in which  primordial material from the creation of the universe would, over time, mature through the lesser metals into pure gold. It was thought that this maturation was prompted by "seeds" of gold contained in the material. In Neri's view, this could be interrupted by various natural circumstances and could be restarted or sped-up through alchemical manipulation.

If one was to "purify" lesser metals into gold, it was advisable to know what needed to be removed. In his manuscript Discorso, Neri carefully explains five categories of impurity, which he then breaks down further into two sub-groups:
It should be noted in general, that in dealing with the [Aristotelian] elements in accordance with chemical philosophy, we can say that all mixed bodies in this art are discovered to contain five kinds of impure substances, which are completely dead and without any virtue or properties effective to [alchemical] operations. Two are from impure substances and three from pure substances, where all the strength, effectiveness and virtue are located specific to each mixture. Of the two [derived from the impure] one is called 'phlegm', which is to say a watery substance with no odor or taste and the other is called 'dead body' [corpo morto] or 'damned earth' [terra dannata], an earthy substance that is equally tasteless and without virtue.[1]
Indeed, in Neri's chemical philosophy, the above two useless forms of impurity (phlegm and corpo morto) are complemented by three useful forms (salt, oil or true sulfur and spirit or mercury), which are present in so-called pure materials. Researcher Maria Grazzini notes in her annotations to the manuscript that: "The chemical philosophy to which Neri refers is Paracelsian, which in addition to the four Aristotelian elements introduces the principal triad (tria prima) of salt, sulfur, and mercury. References to sulfur and mercury were already present in Arabic alchemy." [2] 
Of the other three [derived from the pure] one is called 'salt' and it is the so-called most fixed substance because it is resistant to the violence of fire; it does not flee or vanish into the air. The second is called 'oil' or 'true sulfur' because of the similarity to it, fatty and viscous. The third is called 'spirit' because it is more spiritual and volatile than all the others and even the slightest heat will cause it to dissipate into the air if it has not been bound to the salt, which is the component fixed by the oil. By its tenacious, slimy nature, [oil] acts to bind the volatile to the fixed. These three types are those of the pure substances, which are called by many other names; 'body', 'soul' [anima], 'spirit'; 'bitter', 'sweet', 'acid'; 'salt', 'sulfur', 'mercury' etc.
In them alone are placed all of the virtue and effectiveness of the minerals, the vegetables and the animals, even if the quantity of pure substance is very small in comparison with the impure in any kind of mixed body. These [three] are found in each mixed quantity of pure substance, in comparison with the ineffectual found in the impure. [3] 
In his view, it is these last three forms of impurity that hold the key to transmutation, which tends to puts dregs in a whole new light.


[1] Grazzini 2012, p. 339.
[2] Ibid, note 45, p. 339.
[3] Ibid, p. 340.
* This post first appeared here on 20August 2014.

Wednesday, May 1, 2019

Report from Parnassus

Rafael - El Parnaso (Vatican, Rome, 1511)
Apollo on Parnassus, (fresco detail). 
In the spring of 1612, Italian glassmaker Antonio Neri finished writing L’Arte Vetraria, and the Holy Office of the Inquisition approved it for publication. The book of glass technical recipes passed the Church’s censors despite it containing a large number of alchemy related methods. Contrary to what we might imagine, they did not have any problems with Neri’s work; in fact, one bureaucrat commented that the book was full of useful information. Remember, this was at the same time that so-called sorcerers and witches were being tortured and executed around Europe. One big difference in this case was intent, or rather the perceived intent of Neri's writing. Another factor was his personal connections. The truth is that alchemy was something of a fad among the wealthy nobility, who used the equipment for everything from making rosewater, to distilling liquor, to quietly trying their hand at transmutation. 

To form a better sense of the public image of the chemical arts in the early seventeenth century, we can turn to the satirical critic Traiano Boccalini, who published a book of his own the same year as Neri. Ragguagli di Parnaso [Reports from Parnassus] was an immediate hit. In fact, it became so popular that he and his sharp tongue were forced to leave Rome for the comparative safety of Venice soon after its completion, and soon after that friends found him dead under suspicious circumstances. Initially, Boccalini had been on good terms with Church officials, but perhaps he had seen a bit too much of the institution's inner workingsEventually, he became bitterly disillusioned and wrote Ragguagli as a collection of fictitious news-sheets. These were patterned after the letters that circulated widely as the forerunners of modern newspapers. His reports took place in the mythical state of “Parnassus,” which struck an uncanny resemblance to contemporary Rome. Its monarch, Apollo, struck an uncanny resemblance to the pope, as the princes of Parnassus did to cardinals, bishops and curia officials. Report LXXXIX is illustrative of what were the more practical fears over alchemy, in this case, some creative wealth building among the clergy. It gives a sense of alchemy’s public persona. Apparently, in real life, there was a crackdown by the Church on chemical apparatus, under the guise of concern for public health. Our author slyly suggests, in the very last line, that it may have had more to do with putting an end to clergy lining their own pockets. 
Apollo [the pope] Prohibits the Princes from the Use of Distillers or Alembics At Home: 
In the past few months here, various ailments have emerged in this state of Parnassus, which have caused in some an extraordinary fatigue with frequent agitation: in many a tenacious fever, a faint pulse and a monstrous appetite: in others an intense stomach ache with an ardent thirst.  
The doctors cannot find a single remedy. However, the true cause of these maladies, by decree of Apollo, was revealed before a recent meeting of the grand Asclepius [Society] of prominent Greek, Latin and Arabic doctors, where it was the subject of long and erudite debate. Because neither the enemies of the grand princes nor other eminent gentlemen were spared, it was doubted whether the sickness was caused artificially by powerful poisons. Furthermore, it is clear these troubles were not only happening nearby.  
And we see several modern princes put great study in their most excellent facilities to prepare in their alembics things other than rose water. They conceal subjects dangerous and heinous with their hidden machinations of poison. This cannot be allowed to be covered up; such a scandal must be exposed with the violence of a dagger.  
His Majesty, concurring with the opinion of the congregation, yesterday morning made a public speech, to issue a strict edict, which forbids princes of any color, from ever keeping distillation or alembic operations at home or outside. However, he allowed similar exercises in the hands of experimenters and herbalists. A thing being extremely foul is the minting of counterfeit money in the night and then by day covering so treacherous a crime by running shops openly making medals for the crown. 

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

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

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

Monday, April 29, 2019

Alchemy School

Frontispiece woodcut from
 De Chemia Senioris, by Zadith ben Hamuel, 1566
A common notion holds that alchemists were eccentrics, lone practitioners working in dingy basements, cut off from the rest of the world. This was a myth already well established in glassmaker Antonio Neri's time, but far from the whole truth. In the early seventeenth century, alchemy was practiced in medicine and pharmacy, in precious metals refining and even in the preparation of artists' supplies. The glassmaker was in good company. Where Antonio Neri received his training is unknown, but there are intriguing clues. 

We turn first to Antonio's own father, Neri Neri, the royal physician to the Medici family. According to historian Giulio Negri, he received his medical degree at the prestigious Studio Fiorentino, the forerunner of today's University of Florence. At the time, it had already been in operation for two centuries, having been granted a charter in 1348 by Holy Roman Emperor Charles IV. The charter was a response to a personal appeal by Archbishop Piero Corsini. Antonio Neri's own distant relative, Ser Giovanni Neri, later became Corsini's secretary, so a family legacy of attendance is not out of the question. That our priest might attend his father's alma mater is pure speculation, but it seems foolish to doubt that he started his alchemy education at his father's knee, in his own home.

The manuscript entitled Treasure of the World that Antonio devoted to "all of alchemy" was completed in 1600, but started two years earlier. On a page near the beginning, dated 1598, the twenty-two year-old clearly identifies himself as a "priest." Church rules forbade anyone from becoming a novice before the age of sixteen, which for Neri would have been in the spring of 1592. Full ordination as a Catholic priest typically took six years, meaning in 1598 Neri only recently underwent the 'laying on of hands' ceremony by the archbishop, confirming his title. The inescapable conclusion is that Neri learned his craft while in seminary and the Church sponsored his education. 

The identity of Neri’s order is a mystery, but the few scattered pieces of the puzzle that we do have allow for some interesting speculation. The list of candidates having some connection to the priest and the means to support, if not supply an education is not long. The five names that stand out are the Dominicans, the Carmelites, the Augustinians, the Knights of Malta and the Benedictines. The Dominicans were noted for their scholarship and ran two apothecaries in Florence. The Carmelites are named in the deposition notes taken by Agnolo della Casa, which identify Neri’s confessor as such. The Augustinians counted a Francesco Neri as abbot of their San Clemente monastery who worked for Don Antonio de’ Medici at the Casino in 1619. Antonio’s aunt, Faustina, apparently entered an Augustinian convent after the death of her husband.  Also, though Neri’s confessor was a Carmelite, he also served as the parish priest of an abbey run by the Canons Regular of the Lateran—an independent Augustinian congregation. The Knights of Malta ran two churches in Florence and Neri can be connected to both.  The knights followed the rule of Augustine and enjoyed a close relationship with the Augustinians. The order traces its roots to the crusades  and has various associations with alchemy such as George Ripley. Their main presence was on Malta, though in 1565 they suffered a devastating defeat there to the Ottomans. Neri was not a knight, but he could have occupied a place in their clergy. In Florence, any resources for schooling in alchemy by the knights would have been overseen by its most prominent local official; that official was Neri’s benefactor Don Antonio de’ Medici, Grand Prior of Pisa. The Benedictines were also associated with Neri’s family and had the means to provide him with an education in alchemy. He was born in the parish district of Benedictine church, San Pier Maggiore. His father was buried in the Cistercian (reformed Benedictine) church of Cestello. His sister  committed to a Benedictine order (the Camaldolese). After his ordination, in 1601, Priest Antonio Neri lived across the street from the Vallombrosan (Benedictine) mother church, Santa Trinita.

In any case, as royal physician Neri's father was an esteemed member of the court and Antonio would have enjoyed rare access to its inner sanctum. The grand duke's own laboratory at the Galleria dei Lavori certainly would have been a familiar haunt for our alchemist-priest.

This post first appeared here in a shorter form on 2 October, 2013.

Friday, April 26, 2019

Filippo Sassetti

Goa, India 1509
Later distinguished as a renowned glassmaker and alchemist, Antonio Neri was born into a patrician household. In the Florentine baptism records, his entry was made on a Thursday, the first of March, 1576. He was born the previous evening, to Dianora Parenti and Neri Neri. His godmother is listed in the document as Ginevra Sassetti. Not a great amount is known about her; she was from a prominent family, at the time in her late fifties. However, there are indications that other members of her family interacted with the Neri's. Her nephew Filippo mentions Antonio's father favorably several times in letters, providing a fascinating glimpse into the way disease was diagnosed and treated.

When Antonio was born, his father Neri Neri was in his early thirties, and already a highly regarded physician. Baccio Valori was director of the famed Laurentian Library in Florence and steward of the Medici's simples (medicinal herbs) garden. He was friend to Neri Neri and godfather to Antonio's oldest sister Lessandra. Between 1583 and 1588, Valori received letters from a mutual friend, Filippo Sassetti, who was living in Goa and Cochin – trading settlements in India. Filippo was a native Florentine; he attended university in Pisa with Valori and they became lifelong friends. After Sassetti's father was forced to sell the family home to pay off a debt. Filippo moved to Lisbon and became a spice trader. Not suited for a desk job, he soon set sail seeking adventure in the orient. 

In a 1586 letter to his old friend Valori, Sassetti discusses an Indian remedy against the plague, with a substance called bezoar. The bezoar stone is a mass that develops and becomes trapped in the digestive systems of certain animals. It often resembles a smooth rock. Some thought ground bezoar to be a universal antidote to any poison. Sassetti was puzzled about how the grindings of bezoar could work to cure the plague. Its Aristotelian elemental properties would not be a match for correcting the imbalance of humors in the body. "This is a principle," he explains, taught to him by Neri Neri. "I have thought about it and I can not understand how it works, because the plague is of the same corruption and this is a lack of heat inherent in the humidity. And the stones, if I recall correctly, they have a cold and dry complexion, hence may not precede the restoration of heat. Messer Neri one time did me the favor of telling me." 

In another letter to Baccio Valori, Sassetti notes that he has collected rare varieties of cinnamon in his travels along the Malibar coast in India. His intention was to rediscover the species thought to be a powerful cure of disease by the ancients. He planned to send a parcel of seeds of these and other medicinal plants. "If it pleases God, in the coming year, I will send this to you, so that you may see it all, together with our Messer Neri Neri, who graces my memories." Later he writes that he is sending Baccio the discourse on cinnamon, which he has compiled, along with some plants. These, it later turned out, were water damaged in the journey. He had hoped for some help from Neri Neri on the question of whether the cinnamon he collected from the island of Zeilan [Ceylon], is the same thing as the curative cinnamon of Mantua described by the ancients. Valori was an authority on these matters in his own right. As librarian for the Medici's imposing collection of books and manuscripts, he had vast academic access. As keeper of the simples garden, he had first hand experience in horticulture and its derivative medicinal cures. 

The principles of "humorism" were passed down from celebrated physicians of the ancient world, like Galen, Hippocrates and Dioscorides. It was thought that the cure of disease was dependent on the restoration of balance between four substances in the body: blood, phlegm, black bile and yellow bile. In turn, each of these was associated with one of the Aristotelian elements: air, water, earth and fire respectively. Each was further associated with specific symptoms and characteristic traits of the patient, even their psychological outlook and physical complexion. This system formed the foundation of Western medicine and was taught and practiced well into the nineteenth century. Although, within Antonio Neri's lifetime newer experimentally based methods did start to take hold. A decade after his father's death, in a 1609 letter, Antonio boasts about his success in curing disease in Antwerp using the methods of the medical upstart Paracelsus. It is unlikely that his father would have approved.

*This post first appeared here 13 August 2014.

Wednesday, April 24, 2019

Tartar Salt

So-called "wine diamonds," (harmless)
Potassium bitartrate deposits which can accumulate
in bottles and barrels of wine
Tartar salt is an example of an alchemist's chemical that is a byproduct of another process, in this case winemaking. In his book L'Arte Vetraria, [1] Antonio Neri uses it in his glassmaking for two very different effects. The first application is to improve the appearance of the glass and the other is to modify colors. In addition to uses in glass, tartar also finds its way into his recipes for red paint made from the dried kermes insect [2] and for cast bronze mirrors, as a flux. (In foundries, a flux keeps the metal bright and shiny while in a molten state). [3]

Neri notes that tartar also went by the name of "gruma" to which we can add the synonyms greppola and argol. He warns readers several times to "leave behind the [dried] powder of the [raw] tartar, which is no good" and that "you should have tartar, from the dregs of red wine, which is better than white wine." [4] Nevertheless, he does specifically use white wine tartar in his recipes for rosichiero, a transparent dark red enamel. [5] In his recipe for producing tartar salt [6] he directs the reader to obtain the raw material from emptied wine barrels, but elsewhere in the book he seems to prefer to use the large crystals of tartar that have “vitrified naturally in bottles of wine.” [7] Chemically, tartar is a potassium compound formed through a reaction with tartaric acid, a major constituent of grape juice. [8] 

The effect of tartar in improving the appearance of glass can be readily explained. Most of the glass that was made in Italy in the seventeenth century used sodium-based additives to lower the melting temperature of finely ground quartz powder; these formulations are known as soda-based glasses. Using potassium compounds can have the same effect and these 'potash' based glasses were predominantly produced in northern Europe where trees and plants rich in potassium were used in glass. Potassium is a heavier element and it produces a denser, more refractive glass, giving it more sparkle, although not as much as lead imparts to crystal. Unfortunately, potassium also makes the glass harder to work for the artisan. Potash glass stiffens more quickly as it cools, whereas soda glass remains workable for a longer time before requiring reheating in the furnace. Many of Neri's recipes blend the two additives, which we can imagine gives some of the advantages of both.

Neri also used tartar to modify color in glass. The effects of tartar are exemplified in a number of passages throughout the book. He uses it as the sole pigment in his recipe for pearl colored glass, but he warns, "Once obtained, you must work the color quickly, because it will dissipate." [9] Conversely, he also uses tartar to produce a black colored enamel, combining it with manganese [oxide], which by itself imparts a magenta color. [10] 

The first step in making Neri's purified tartar salt is to obtain the raw "gruma, from barrels of red wine in which it forms large lumps." Next, he gently roasts it in terracotta pots "until it becomes calcined black and all its sliminess is roasted away. It then will begin to whiten, but do not let it become white, because if you do the salt will be no good." Now, he boils it in water for two hours, evaporating off three-quarters of the liquid. After filtering, he lets the remaining liquid "lye" cool in pans, allowing any sediment to settle to the bottom. He gently pours off  (decants)  the liquid which is further processed on the stove, this time in glass containers. The result, after full evaporation over a slow fire is a “white salt” left in the vessel. He dissolves this in hot water, filters it again and allows more sediment to settle out for a period of two days. Again, the liquid is decanted and evaporated in a glass container. The filtering and evaporation process is repeated four times, resulting in a product that is "whiter than snow."

Neri's final remarks for this chapter are as follows:
“When mixed with sifted polverino, or rocchetta, with its doses of tarso or sand, this salt will make a frit that in crucibles will produce the most beautiful cristallino and common glass, which one cannot make without the accompaniment of tartar salt. Without it, good fine cristallino can be made, nevertheless with it, it will be the absolute most beautiful.” [11]

[1] Neri 1612.
[2] Ibid, ch 116, 117.
[3] Ibid, ch 113. Note that in glassmaking, the term 'flux' has a different meaning than in metallurgy.
[4] Ibid,  ch 41. 
[5] Ibid, ch 125.
[6] Ibid, ch 11.
[7] Ibid. ch 46.
[8] Pure tartar takes the form potassium bitartrate KHC4H4O6.
[9] Neri 1612, ch 60.
[10] Ibid, ch 102.
[11] Ibid, ch 11. Polverino and rocchetta are thought to be forms of dried Salsola Kali plants. Tarso is Neri's term for white quartz river stones. Cristallino was a Venetian style glass that in quality fell between common glass and the premium cristallo, for which Murano became famous.
* This post first appeared here on 5 Sept. 2014.

Monday, April 22, 2019

Art and Science

Jacopo Ligozzi,1518,  fanciful glass vessels,
ink and watercolor on paper.
Antonio Neri's writing on glassmaking and alchemy was distinguished from that of many contemporary authors in that his work was all deeply rooted in hands-on experience. He worked in the early 17th century, when art and science were different sides of the same endeavour to understand the world. His contemporaries were often content to repeat century's old teachings about the four Aristotelian elements; that chemical interactions could be explained through an analysis of the balance between hot and cold, dry and wet. But more and more, these notions were being discarded and replaced. It is common to cite the invention of instruments, and other technical developments; these factors certainly did contribute to advancement. But many different forces worked toward the emergence of early modern science, and one in particular is so obvious that it is easily overlooked: artists.

Working with hot glass was a profession in which attention to nature was essential: artists did not have the luxury of fanciful explanations of physical processes. They were obliged by their work to learn the ways glass mixed, moved and behaved in the furnace, not as they imagined it should, but as it actually did. The only way to achieve the complex forms and vessels for which master glassblowers were renowned was through long experience. Failure to understand the glass and predict its properties accurately resulted in failure of the piece.


Neri was immersed in this environment and the same principles applied to his own work in formulating the glass. Ancient theories had little value if they did not accurately predict nature. Like the glass artists, the way forward for Neri was careful attention and hands-on experience. He learned the value of starting with highly purified ingredients for his glass melts. He learned that too much glass salt resulted in a putrid 'gall' that would need to be skimmed off the molten surface. Substituting salts made from fern plants, for the Kali based ones from the Levant, produced a more lustrous glass, yet it stiffened more quickly for the glassblowers.


A glass artist's work also serves as a kind of narrative. For those familiar with the techniques, a finished piece of glass work can be 'read' like a story: The handles were put on last, before that, perhaps a thin bead of color was applied to the lip of the vessel. And the work started as a blown bubble of glass, shaped and opened with special tools. Each step is an insight into the artist's technique, but also into the way nature itself operates. Each motion was a well practiced negotiation between the artist and the properties of the material.


On one hand, an artist's job was to produce objects contemplated for their physical beauty and cultural significance. On the other hand, the act of producing these objects created an environment where accurate reasoning flourished. By collecting artists and employing them together, the Medici rulers of Tuscany were creating a cauldron effect where experiences collected, stewed and nature's secrets unraveled.


* This post first appeared here on 23 October 2013.

Friday, April 19, 2019

Carries the Palm

Jesus' entry into Jerusalem, walking on palm leaves.
 Pietro Lorenzetti 1320
For Western Christians, this week began with "Palm Sunday," a feast day that falls on the Sunday before Easter and celebrates Jesus' entry into Jerusalem. His procession is said to have included his followers laying palm tree leaves before him along his path. The connection to seventeenth century priest and glassmaker Antonio Neri is this: In his book L'Arte Vetraria, Neri describes his very best green glass with a colloquial expression; saying the recipe "carries the palm" for all other greens.   


Saint Justina of Padua with a palm frond,
Bartolo Montagna 1490s
In his book, Neri presents a string of recipes for variations of green glass. Finally, in chapter 35, he presents his ultimate green, which he titles: "Another Green, Which 'Carries the Palm' for All Other Greens, Invented by Me." The phrase "carries the palm" alludes to the biblical story of Jesus entering Jerusalem, in which the people welcomed him by laying down cloth and palm branches on the ground in his path. Even before that, the palm branch served as a symbol of victory; in ancient Greece, palm fronds were awarded to victorious athletes. Later in history, Roman lawyers who won a case decorated their doors with palm leaves.


Copper Sulfate (vitriol of copper)
Cristallino was a mid-grade glass made with a soda based plant ash from the Levant which Neri called "rocchetta." For this recipe, he blends it with common glass, and adds red lead oxide to the mix, in effect forming an early version of what we now call lead crystal. He "cleans" the glass by using the well-established technique of flinging the molten glass into a large tub of clean water. This had the effect of "washing out" excess glass salt (flux). In addition, it provided the opportunity to sort through the fragments to remove any undissolved metallic lead. Lead that did not go into the glass had the tendency to collect at the bottom of the clay crucible as lumps of molten metal. It could then eat a hole in the vessel, resulting in a glass-shop disaster, as Neri warns: 
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. Then add the color using the powder, made chemically by the dry distillation of vitriol of copper [chapter 31]. Also, add a little crocus of iron, but very little. The result will be a most marvelous beautiful green, the best that I ever made. It will seem just like an emerald of ancient oriental rock, and you can use it in every sort of job.
The "crocus of iron" mentioned above is simply iron oxide or 'rust' as it is more commonly known. The "vitriol of copper" he refers to is copper sulfate. Neri forms it in a laborious process that involves cutting copper sheet into small, coin-sized pieces, mixing it with sulfur, heating in the furnace and then reprocessing it several times. The result is then added to water and the soluble part is further processed, filtered and evaporated. The final product is a pure blue crystalline material that has uses for our alchemist that go far beyond glassmaking, as he alludes to in the final sentence of 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.
*This post first appeared her in a slightly different form on 25 October 2013.