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.

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.

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.

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.

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.

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.

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.