Sulfur of Saturn

 

The Roman Goddess Ops, 'sweet'-heart (and wife)

of Saturn, Peter Paul Rubens c. 1630,

“Abundance (Abundantia).” [1]

Antonio Neri’s 1612 book on glassmaking, L'Arte Vetraria, devotes an entire chapter to making artificial gems. These are made with an especially dense, refractive form of lead glass—what today would be called lead crystal. He made it in small batches, in sealed ceramic vessels; each infused with various metal oxide pigments to give characteristic jewel tone colors.  His secret ingredient for making the finest artificial gems was a material known as "sulfur of Saturn." He writes:

You will have jewels of marvelous beauty in every color, which by far surpass those described above, made with ordinary minium. Because with this true sulfur of Saturn, they will surpass all others by far more than I can write here, as I have seen and made many times in Antwerp.[2]

This "ordinary minium" that he speaks of is one of several oxide forms of lead, also known as 'red lead,' it is bright red or orange in color. As a stable red pigment it was well known to ancient Byzantine and Persian illuminators. [3] It was so popular, in fact, that the word used to describe small intricate pictures 'miniature,' is derived directly from 'minium.' [4] The intricate embellishments in manuscripts ultimately took on the name of the scribes' favorite color.  In glass, minium does not impart red or any other color on its own, but does add 'sparkle' and made Neri's jewels highly refractive to light. 

In the recipe, he uses white vinegar and he reacts it with finely ground minium through a laborious process. The acetic acid in vinegar chemically combines with the minium to form lead acetate, which alchemists called "sugar of Saturn" because it had a distinctively sweet taste (more on that later). [5] Lead (Saturn) could be added to the melt in a number of different forms including acetate, carbonate and various oxides. The heat of the furnace reduces them all and the result is essentially identical glass from any of these sources. The lead acetate has one major advantage that set it apart from the others. Lead acetate is soluble in water and therefore it can easily be purified of contaminants and to a much higher degree. It can be filtered, allowed to stand and decanted after any insoluble impurities settle out.

In other references "sugar of Saturn" and "sulfur of Saturn" are considered synonyms. This is not the case with Neri, for him they are two different substances; the 'sugar' is a precursor for his final product, sulfur of Saturn:

Left in the bottom will be a salt as white as snow, and as sweet as sugar. Repeat the dissolution, and filtering, and evaporation with common water three times. This is the required sugar of Saturn. 

Keep it to calcine in sand in a glass flask or ball in a furnace over a moderated fire for many days. It will further calcine to a color that is much redder than cinnabar, and more finely impalpable than sifted grain flour. This is the required true sulfur of Saturn; purified from the sediment, foulness and blackness that were upon the lead at first. [6]

It would be a reasonable guess that by heating the acetate for "many days" he is reducing it back to minium, its more basic, bright red oxide state, but this time in a greatly purified form.

Unfortunately for his health, in this recipe for sulfur of Saturn, Antonio makes extensive use of heating and evaporation. Even more unfortunate is that in a number of steps he judges the potency of his product by taste. Lead acetate is highly toxic; because it is soluble in water, it enters the bloodstream easily. It attacks the nervous system, accumulates in the bones and can cause organ failure. It is quite likely that by breathing the fumes and tasting crystals of sugar of Saturn, Neri was contributing to his own demise at the relatively young age of thirty-eight. Lead acetate was not the only toxic substance he handled regularly, but it was certainly one of the worst for his health. 

 It does not follow that he was totally ignorant of the risks he was taking. The dangers of heavy metals were recognized from early times. Pliny speaks of the noxious fumes from lead furnaces, and Plutarch opined that lead and mercury mines were "unwholesome and pestilent places." Neri’s own father followed the work of Dioscorides, who wrote that ceruse (lead carbonate), taken internally, could be fatal and that as a sweetener for wines could adversely affect the abdomen and the nerves.

Ancient Romans discovered that when wine started to turn to vinegar, it could be boiled down in lead lined pots to produce a highly sweet syrup called sapa. A late Roman cookbook made extensive use of sapa, which presumably contained considerable lead acetate. [7] It has been conjectured that  lead laced sapa contributed to poisoning among the Roman aristocracy. While lead acetate is a deadly poison, it may be a step too far to imply that it contributed to the fall of the Roman Empire.

[1] Alchemical tradition does provide for an association between the metal lead and the Roman god Saturn. However, there is no such association between 'sugar of Saturn' and either of his consorts Ops or Lua, although Ops, the goddess of abundance (opulence) does rather nicely represent the chemical that made Neri's most opulent artificial gems possible.
[2] Neri 1612, ch. 91.
[3] Chemically, this is Pb3O4, also known as Lead (II,IV) oxide, triplumbic tetroxide. Historically, it was called minium and red lead.
[4] The accepted etymology of ‘miniature’ is from ‘minium,’ but may have been influenced by similar Latin terms such as  minor, minimus, minutus, etc.
[5] Lead acetate comes in two forms; Pb (C2H3O2)4 and Pb (C2H3O2)2, both are toxic; the later variety is soluble in water.
[6] Neri 1612, ch. 91.
[7] “Saba” endures today as a popular grape syrup, albeit without the lead.
* This post forst appeared here on 12 September 2014.

Paste Gems

Pastes (glass) set in silver openwork (Portugal c. 1750)

Victoria and Albert Museum, London.

Acq. nr. M.68-1962

In many ways, the story of artificial gems traces the story of glass technology itself. From ancient times, when glass could only be produced in very small quantities it was regarded and used as a type of stone that was made through art. Alchemists thought the bright colors produced by metallic pigments in glass were a key to the philosopher's stone, and the transmutation of base metals into gold. As the technical prowess of glassmakers expanded, so did the ability to simulate specific stones, most notably coveted gems. Glass went on to be used as material for utilitarian objects like goblets and as an indispensable part of scientific enquiry. All the while, artificial gems have continued to dazzle us with their beauty. 

In the fifth part of Antonio Neri's 1612 book, he teaches the secrets of making artificial gems "of so much grace, and beauty, that they will surpass the natural stones in everything except hardness." It is not a difficult argument to make that this section alone is responsible for much of the lasting popularity of L'Arte Vetraria. It is easy to see why enterprising artisans would want to make glass imitations that could pass for the real thing. It is also perhaps tempting to jump to the conclusion that Neri intended his recipes to be used in deception, but there is no evidence whatsoever that this was the case.

Neri gives full credit for his innovative methods in paste gems to Dutch alchemist Isaac Hollandus. Hollandus is an enigmatic figure, whose writings survive, but not much is known of the man, his family, or even if he was living in Neri's time. What is known is that Antonio's dear friend Emmanuel Ximenes was the brother-in-law to Baron Simon Rodriguez d'Evora, a famous diamond dealer and jeweler of choice to royalty throughout Europe. He lived and worked on the same street in Antwerp as Ximenes' palace, only a few steps away from Neri's new temporary home. It was a common request of wealthy patrons to have duplicate jewelry made in paste for travel and security reasons. If a fake necklace or jewel could pass for the real thing, it was well worth the added expense, when the genuine article could remain safe under lock and key.

No artificial gem recipes have ever been found among Hollandus' writings, excepting one for ruby which is then crushed up as part of a prescription for the philosopher's stone. It is quite possible that Neri was applying a more general technique from the Dutchman. The basic material for all of Neri's paste gems is a fine lead crystal. The crux of his innovation lay in the form of lead used. Normally, metallic lead sheet was cut into small pieces, and roasted in a kiln such that it would oxidize into powder, but not melt. The powder was then added to the glass melt. In Neri's method the lead was chemically converted into a water-soluble form, which could then be filtered and purified to a much greater extent. The end result was a far better grade of crystal.

In 1697, Jean Haudicquer de Blancourt translated into French and greatly expanded Christopher Merrett's English edition of Neri. Blancourt gave no credit to the Italian for his work, and two years later, when it was translated back into English by Daniel Brown, the connection to Neri was completely lost, but the credit for paste gems remained with Hollandus. In the eighteenth and nineteenth centuries, numerous general encyclopedias of art and craft were published and the so-called 'Hollandus' paste gem recipes turned up many times. Meanwhile, a properly credited French version of L'Arte Vetraria was completed by Holbach in 1752. This edition was more suited to a scientific audience; he faithfully translated the Italian, but also incorporated the full comments of Merrett as well as those of Kunckel who issued his famous German version of Neri in 1679.

For more reading on Neri's artificial gems see Glass as Pasta and on the work of later investigators see Marieke Hendriksen at The Medicine Chest

Lead Crystal

 

Roemer type drinking glass c. 1677,

George Ravenscroft.

The entire fourth part of Antonio Neri's 1612 book L'Arte Vetraria is devoted to the preparation of lead glass, a forerunner of what is now commonly known as lead crystal. This section is unique in the book in that it contains the only instance of the author giving direct advice to glass artists themselves:

"To work lead glass into various drinking glasses or other vessels, or even to draw cane for beadmaking, it is necessary to raise the punty [out of the melt], and to make a gather of glass by turning. Take it out, let it cool somewhat and then work it on a well-cleaned marble [marver]. The marble should be somewhat cool, and well bathed with water before use."

He goes on to describe what might be termed a kind of dance with the glass. As with a human partner, gentle patience is required in learning the boundaries of what can and cannot be done. Ultimately, an artist must come to understand the material's behavior and personality in order to result in a great partnership. For the artist who makes unrealistic demands, glass can be a heartbreaker.  

"This sort of glass, lead glass, is so runny that were it not cooled, and taken up by turning [the punty] to wind a gather, it would be impossible to work. It is so runny that it would not even hold onto the punty, because it is as loose as soup. This arises out of [the fact that] the lead calx causes it to become very fluid."

"Namely, gather the glass little by little, allow it to cool, and work it over marble frequently bathed in water. Furthermore, make sure to keep the pot of glass rather calm, and in a place in the furnace where it will not see too much heat, otherwise it will not be possible to work this glass at all."

The formulation of lead crystal as we know it is a relatively recent development. This is a composition of crushed silica (sand or quartz), potash (potassium carbonates) and lead oxide substituting for calcium to stabilize the composition. It is also true that lead has been added to glass since its invention a few thousand years ago. It is not clear that this addition was always intentional, but a Babylonian tablet of 1700 BCE gives a recipe for pottery glaze that explicitly contains lead. At some point, a discovery showed that small amounts of lead and pigment smeared on glass and fired made stained glass paintings possible. The earliest known examples of colored stained glass windows date to 800-820 (San Vicenzo Abbey excavation in Volturno, Italy.)  In medieval Europe, leading up to Antonio Neri's time, lead glass was used in mosaic tesserae and in artificial gems.

Finally, it is worth noting that Neri's childhood church in Florence, Cestello (now called Santa Maria Maddalena dei Pazzi), was then run by Cistercian monks. It was the Cistercian luminary St. Bernard of Clairvaux who, in the twelfth century, built the first church with large windows, urging, "The soul shall seek the light by following the light."

This post first appeared here 15 November 2013.

Artificial Gems

Pastes (glass) set in silver openwork (Portugal c. 1750)

Victoria and Albert Museum, London.

Acq. nr. M.68-1962

In many ways, the story of artificial gems traces the story of glass technology itself. From ancient times, when glass could only be produced in very small quantities it was regarded and used as a type of stone that was made through art. Alchemists thought the bright colors produced by metallic pigments in glass were a key to the philosopher's stone, and the transmutation of base metals into gold. As the technical prowess of glassmakers expanded, so did the ability to simulate specific stones, most notably coveted gems. Glass went on to be used as material for utilitarian objects like goblets and as an indispensable part of scientific enquiry. All the while, artificial gems have continued to dazzle us with their beauty. 

In the fifth part of Antonio Neri's 1612 book, he teaches the secrets of making artificial gems "of so much grace, and beauty, that they will surpass the natural stones in everything except hardness." It is not a difficult argument to make that this section alone is responsible for much of the lasting popularity of L'Arte Vetraria. It is easy to see why enterprising artisans would want to make glass imitations that could pass for the real thing. It is also perhaps tempting to jump to the conclusion that Neri intended his recipes to be used in deception, but there is no evidence whatsoever that this was the case.

Neri gives full credit for his innovative methods in paste gems to Dutch alchemist Isaac Hollandus. Hollandus is an enigmatic figure, whose writings survive, but not much is known of the man, his family, or even if he was living in Neri's time. What is known is that Antonio's dear friend Emmanuel Ximenes was the brother-in-law to Baron Simon Rodriguez d'Evora, a famous diamond dealer and jeweler of choice to royalty throughout Europe. He lived and worked on the same street in Antwerp as Ximenes' palace, only a few steps away from Neri's new temporary home. It was a common request of wealthy patrons to have duplicate jewelry made in paste for travel and security reasons. If a fake necklace or jewel could pass for the real thing, it was well worth the added expense, when the genuine article could remain safe under lock and key.

No artificial gem recipes have ever been found among Hollandus' writings, excepting one for ruby which is then crushed up as part of a prescription for the philosopher's stone. It is quite possible that Neri was applying a more general technique from the Dutchman. The basic material for all of Neri's paste gems is a fine lead crystal. The crux of his innovation lay in the form of lead used. Normally, metallic lead sheet was cut into small pieces, and roasted in a kiln such that it would oxidize into powder, but not melt. The powder was then added to the glass melt. In Neri's method the lead was chemically converted into a water-soluble form, which could then be filtered and purified to a much greater extent. The end result was a far better grade of crystal.

In 1697, Jean Haudicquer de Blancourt translated into French and greatly expanded Christopher Merrett's English edition of Neri. Blancourt gave no credit to the Italian for his work, and two years later, when it was translated back into English by Daniel Brown, the connection to Neri was completely lost, but the credit for paste gems remained with Hollandus. In the eighteenth and nineteenth centuries, numerous general encyclopedias of art and craft were published and the so-called 'Hollandus' paste gem recipes turned up many times. Meanwhile, a properly credited French version of L'Arte Vetraria was completed by Holbach in 1752. This edition was more suited to a scientific audience; he faithfully translated the Italian, but also incorporated the full comments of Merrett as well as those of Kunckel who issued his famous German version of Neri in 1679.

For more reading on Neri's artificial gems see Glass as Pasta and on the work of later investigators see Marieke Hendriksen at The Medicine Chest

Cross Pollination

The art of stonework,

from MS Ferguson 67, f. 7r, (1598-1600)

Antonio Neri.

Throughout the Renaissance, Florence, Italy was famous for its artistic output. Names like Donatello, Michelangelo and Giambologna graced the tongues of patrons across Europe. But the secret to the city’s fantastic creativity did not rest solely on individual superstars. The ruling Medici family had found a way to harness the talents of myriad lesser known artisans and use the fruits of their creative labor as a powerful political tool. 

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

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

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

This culture of cross pollination can be seen throughout Antonio Neri's work, in the variety of different glass recipes and also in his knowledge of the ways his glass was to be used. In his 1612 book, L'Arte Vetraria, he says:

Because in order to make vessels and drinking glasses where the glass is thin, you must really load it with a lot of color, but for making large cane for beads not so great a charge of color is necessary. For making thin cane for small beads, you must charge it well with color. In working the glass, you must apportion it with more or less color according to the purpose it must serve.

For lead crystal artisans, he has this advice:

To work lead glass into various drinking glasses or other vessels, or even to draw cane for beadmaking, it is necessary to raise the punty [out of the melt], and to make a gather of glass by turning. Take it out, let it cool somewhat and then work it on a well-cleaned marble [marver]. The marble should be somewhat cool, and well bathed with water before use.

This practice will ensure that the paste of the lead glass does not pull up any of the marble. The glass will always gall marble not bathed in water. Some chips will incorporate into the work, giving it an ugly look. Therefore, frequently flush the marble with fresh water for as long as you are working the glass. Otherwise, all its grace and beauty will be lost.

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

*This post first appeared here on 19 March 2014.

Sulfur of Saturn

The Roman Goddess Ops, 'sweet'-heart (and wife)

of Saturn, Peter Paul Rubens c. 1630,

“Abundance (Abundantia).” [1]

Antonio Neri’s 1612 book on glassmaking, L'Arte Vetraria, devotes an entire chapter to making artificial gems. These are made with an especially dense, refractive form of lead glass—what today would be called lead crystal. He made it in small batches, in sealed ceramic vessels; each infused with various metal oxide pigments to give characteristic jewel tone colors.  His secret ingredient for making the finest artificial gems was a material known as "sulfur of Saturn." He writes:

You will have jewels of marvelous beauty in every color, which by far surpass those described above, made with ordinary minium. Because with this true sulfur of Saturn, they will surpass all others by far more than I can write here, as I have seen and made many times in Antwerp.[2]

This "ordinary minium" that he speaks of is one of several oxide forms of lead, also known as 'red lead,' it is bright red or orange in color. As a stable red pigment it was well known to ancient Byzantine and Persian illuminators. [3] It was so popular, in fact, that the word used to describe small intricate pictures 'miniature,' is derived directly from 'minium.' [4] The intricate embellishments in manuscripts ultimately took on the name of the scribes' favorite color.  In glass, minium does not impart red or any other color on its own, but does add 'sparkle' and made Neri's jewels highly refractive to light. 

In the recipe, he uses white vinegar and he reacts it with finely ground minium through a laborious process. The acetic acid in vinegar chemically combines with the minium to form lead acetate, which alchemists called "sugar of Saturn" because it had a distinctively sweet taste (more on that later). [5] Lead (Saturn) could be added to the melt in a number of different forms including acetate, carbonate and various oxides. The heat of the furnace reduces them all and the result is essentially identical glass from any of these sources. The lead acetate has one major advantage that set it apart from the others. Lead acetate is soluble in water and therefore it can easily be purified of contaminants and to a much higher degree. It can be filtered, allowed to stand and decanted after any insoluble impurities settle out.

In other references "sugar of Saturn" and "sulfur of Saturn" are considered synonyms. This is not the case with Neri, for him they are two different substances; the 'sugar' is a precursor for his final product, sulfur of Saturn:

Left in the bottom will be a salt as white as snow, and as sweet as sugar. Repeat the dissolution, and filtering, and evaporation with common water three times. This is the required sugar of Saturn. 

Keep it to calcine in sand in a glass flask or ball in a furnace over a moderated fire for many days. It will further calcine to a color that is much redder than cinnabar, and more finely impalpable than sifted grain flour. This is the required true sulfur of Saturn; purified from the sediment, foulness and blackness that were upon the lead at first. [6]

It would be a reasonable guess that by heating the acetate for "many days" he is reducing it back to minium, its more basic, bright red oxide state, but this time in a greatly purified form.

Unfortunately for his health, in this recipe for sulfur of Saturn, Antonio makes extensive use of heating and evaporation. Even more unfortunate is that in a number of steps he judges the potency of his product by taste. Lead acetate is highly toxic; because it is soluble in water, it enters the bloodstream easily. It attacks the nervous system, accumulates in the bones and can cause organ failure. It is quite likely that by breathing the fumes and tasting crystals of sugar of Saturn, Neri was contributing to his own demise at the relatively young age of thirty-eight. Lead acetate was not the only toxic substance he handled regularly, but it was certainly one of the worst for his health. 

 It does not follow that he was totally ignorant of the risks he was taking. The dangers of heavy metals were recognized from early times. Pliny speaks of the noxious fumes from lead furnaces, and Plutarch opined that lead and mercury mines were "unwholesome and pestilent places." Neri’s own father followed the work of Dioscorides, who wrote that ceruse (lead carbonate), taken internally, could be fatal and that certain sweet wines could adversely affect the abdomen and the nerves.

Ancient Romans discovered that when wine started to turn to vinegar, it could be boiled down in lead lined pots to produce a highly sweet syrup called sapa. A late Roman cookbook made extensive use of sapa, which presumably contained considerable lead acetate. [7] It has been conjectured that  lead laced sapa contributed to poisoning among the Roman aristocracy. While lead acetate is a deadly poison, it is a step too far to imply that it contributed to the fall of the Roman Empire.

[1] Alchemical tradition does provide for an association between the metal lead and the Roman god Saturn. However, there is no such association between 'sugar of Saturn' and either of his consorts Ops or Lua, although Ops, the goddess of abundance (opulence) does rather nicely represent the chemical that made Neri's most opulent artificial gems possible.
[2] Neri 1612, ch. 91.
[3] Chemically, this is Pb3O4, also known as Lead (II,IV) oxide, triplumbic tetroxide. Historically, it was called minium and red lead.
[4] The accepted etymology of ‘miniature’ is from ‘minium,’ but may have been influenced by similar Latin terms such as  minor, minimus, minutus, etc.
[5] Lead acetate comes in two forms; Pb (C2H3O2)4 and Pb (C2H3O2)2, both are toxic; the later variety is soluble in water.
[6] Neri 1612, ch. 91.
[7] “Saba” endures today as a popular grape syrup, albeit without the lead.
* This post forst appeared here on 12 September 2014.

Lead Crystal

Roemer type drinking glass c. 1677,

George Ravenscroft.

The entire fourth part of Antonio Neri's 1612 book L'Arte Vetraria is devoted to the preparation of lead glass, a forerunner of what is now commonly known as lead crystal. This section is unique in the book in that it contains the only instance of the author giving direct advice to glass artists themselves:

"To work lead glass into various drinking glasses or other vessels, or even to draw cane for beadmaking, it is necessary to raise the punty [out of the melt], and to make a gather of glass by turning. Take it out, let it cool somewhat and then work it on a well-cleaned marble [marver]. The marble should be somewhat cool, and well bathed with water before use."

He goes on to describe what might be termed a kind of dance with the glass. As with a human partner, gentle patience is required in learning the boundaries of what can and cannot be done. Ultimately, an artist must come to understand the material's behavior and personality in order to result in a great partnership. For the artist who makes unrealistic demands, glass can be a heartbreaker.  

"This sort of glass, lead glass, is so runny that were it not cooled, and taken up by turning [the punty] to wind a gather, it would be impossible to work. It is so runny that it would not even hold onto the punty, because it is as loose as soup. This arises out of [the fact that] the lead calx causes it to become very fluid."

"Namely, gather the glass little by little, allow it to cool, and work it over marble frequently bathed in water. Furthermore, make sure to keep the pot of glass rather calm, and in a place in the furnace where it will not see too much heat, otherwise it will not be possible to work this glass at all."

The formulation of lead crystal as we know it is a relatively recent development. This is a composition of crushed silica (sand or quartz), potash (potassium carbonates) and lead oxide substituting for calcium to stabilize the composition. It is also true that lead has been added to glass since its invention a few thousand years ago. It is not clear that this addition was always intentional, but a Babylonian tablet of 1700 BCE gives a recipe for pottery glaze that explicitly contains lead. At some point, a discovery showed that small amounts of lead and pigment smeared on glass and fired made stained glass paintings possible. The earliest known examples of colored stained glass windows date to 800-820 (San Vicenzo Abbey excavation in Volturno, Italy.)  In medieval Europe, leading up to Antonio Neri's time, lead glass was used in mosaic tesserae and in artificial gems.

Finally, it is worth noting that Neri's childhood church in Florence, Cestello (now called Santa Maria Maddalena dei Pazzi), was then run by Cistercian monks. It was the Cistercian luminary St. Bernard of Clairvaux who, in the twelfth century, built the first church with large windows, urging, "The soul shall seek the light by following the light."

This post first appeared here 15 November 2013.

Sulfur of Saturn

The Roman Goddess Ops, 'sweet'-heart (and wife)

of Saturn, Peter Paul Rubens c. 1630,

“Abundance (Abundantia).” [1]

Antonio Neri’s 1612 book on glassmaking, L'Arte Vetraria, devotes an entire chapter to making artificial gems. These are made with an especially dense, refractive form of lead glass—what today would be called lead crystal. He made it in small batches, in sealed ceramic vessels; each infused with various metal oxide pigments to give characteristic jewel tone colors.  His secret ingredient for making the finest artificial gems was a material known as "sulfur of Saturn." He writes:

You will have jewels of marvelous beauty in every color, which by far surpass those described above, made with ordinary minium. Because with this true sulfur of Saturn, they will surpass all others by far more than I can write here, as I have seen and made many times in Antwerp.[2]

This "ordinary minium" that he speaks of is one of several oxide forms of lead, also known as 'red lead,' it is bright red or orange in color. As a stable red pigment it was well known to ancient Byzantine and Persian illuminators. [3] It was so popular, in fact, that the word used to describe small intricate pictures 'miniature,' is derived directly from 'minium.' [4] The intricate embellishments in manuscripts ultimately took on the name of the scribes' favorite color.  In glass, minium does not impart red or any other color on its own, but does add 'sparkle' and made Neri's jewels highly refractive to light. 

In the recipe, he uses white vinegar and he reacts it with finely ground minium through a laborious process. The acetic acid in vinegar chemically combines with the minium to form lead acetate, which alchemists called "sugar of Saturn" because it had a distinctively sweet taste (more on that later). [5] Lead (Saturn) could be added to the melt in a number of different forms including acetate, carbonate and various oxides. The heat of the furnace reduces them all and the result is essentially identical glass from any of these sources. The lead acetate has one major advantage that set it apart from the others. Lead acetate is soluble in water and therefore it can easily be purified of contaminants and to a much higher degree. It can be filtered, allowed to stand and decanted after any insoluble impurities settle out.

In other references "sugar of Saturn" and "sulfur of Saturn" are considered synonyms. This is not the case with Neri, for him they are two different substances; the 'sugar' is a precursor for his final product, sulfur of Saturn:

Left in the bottom will be a salt as white as snow, and as sweet as sugar. Repeat the dissolution, and filtering, and evaporation with common water three times. This is the required sugar of Saturn. 

Keep it to calcine in sand in a glass flask or ball in a furnace over a moderated fire for many days. It will further calcine to a color that is much redder than cinnabar, and more finely impalpable than sifted grain flour. This is the required true sulfur of Saturn; purified from the sediment, foulness and blackness that were upon the lead at first. [6]

It would be a reasonable guess that by heating the acetate for "many days" he is reducing it back to minium, its more basic, bright red oxide state, but this time in a greatly purified form.

Unfortunately for his health, in this recipe for sulfur of Saturn, Antonio makes extensive use of heating and evaporation. Even more unfortunate is that in a number of steps he judges the potency of his product by taste. Lead acetate is highly toxic; because it is soluble in water, it enters the bloodstream easily. It attacks the nervous system, accumulates in the bones and can cause organ failure. It is quite likely that by breathing the fumes and tasting crystals of sugar of Saturn, Neri was contributing to his own demise at the relatively young age of thirty-eight. Lead acetate was not the only toxic substance he handled regularly, but it was certainly one of the worst for his health. 

 It does not follow that he was totally ignorant of the risks he was taking. The dangers of heavy metals were recognized from early times. Pliny speaks of the noxious fumes from lead furnaces, and Plutarch opined that lead and mercury mines were "unwholesome and pestilent places." Neri’s own father followed the work of Dioscorides, who wrote that ceruse (lead carbonate), taken internally, could be fatal and that as a sweetener for wines could adversely affect the abdomen and the nerves.

Ancient Romans discovered that when wine started to turn to vinegar, it could be boiled down in lead lined pots to produce a highly sweet syrup called sapa. A late Roman cookbook made extensive use of sapa, which presumably contained considerable lead acetate. [7] It has been conjectured that  lead laced sapa contributed to poisoning among the Roman aristocracy. While lead acetate is a deadly poison, it may be a step too far to imply that it contributed to the fall of the Roman Empire.

[1] Alchemical tradition does provide for an association between the metal lead and the Roman god Saturn. However, there is no such association between 'sugar of Saturn' and either of his consorts Ops or Lua, although Ops, the goddess of abundance (opulence) does rather nicely represent the chemical that made Neri's most opulent artificial gems possible.
[2] Neri 1612, ch. 91.
[3] Chemically, this is Pb3O4, also known as Lead (II,IV) oxide, triplumbic tetroxide. Historically, it was called minium and red lead.
[4] The accepted etymology of ‘miniature’ is from ‘minium,’ but may have been influenced by similar Latin terms such as  minor, minimus, minutus, etc.
[5] Lead acetate comes in two forms; Pb (C2H3O2)4 and Pb (C2H3O2)2, both are toxic; the later variety is soluble in water.
[6] Neri 1612, ch. 91.
[7] “Saba” endures today as a popular grape syrup, albeit without the lead.
* This post forst appeared here on 12 September 2014.

Artificial Gems

Pastes (glass) set in silver openwork (Portugal c. 1750)

Victoria and Albert Museum, London.

Acq. nr. M.68-1962

In many ways, the story of artificial gems traces the story of glass technology itself. From ancient times, when glass could only be produced in very small quantities it was regarded and used as a type of stone that was made through art. Alchemists thought the bright colors produced by metallic pigments in glass were a key to the philosopher's stone, and the transmutation of base metals into gold. As the technical prowess of glassmakers expanded, so did the ability to simulate specific stones, most notably coveted gems. Glass went on to be used as material for utilitarian objects like goblets and as an indispensable part of scientific enquiry. All the while, artificial gems have continued to dazzle us with their beauty. 

In the fifth part of Antonio Neri's 1612 book, he teaches the secrets of making artificial gems "of so much grace, and beauty, that they will surpass the natural stones in everything except hardness." It is not a difficult argument to make that this section alone is responsible for much of the lasting popularity of L'Arte Vetraria. It is easy to see why enterprising artisans would want to make glass imitations that could pass for the real thing. It is also perhaps tempting to jump to the conclusion that Neri intended his recipes to be used in deception, but there is no evidence whatsoever that this was the case.

Neri gives full credit for his innovative methods in paste gems to Dutch alchemist Isaac Hollandus. Hollandus is an enigmatic figure, whose writings survive, but not much is known of the man, his family, or even if he was living in Neri's time. What is known is that Antonio's dear friend Emmanuel Ximenes was the brother-in-law to Baron Simon Rodriguez d'Evora, a famous diamond dealer and jeweler of choice to royalty throughout Europe. He lived and worked on the same street in Antwerp as Ximenes' palace, only a few steps away from Neri's new temporary home. It was a common request of wealthy patrons to have duplicate jewelry made in paste for travel and security reasons. If a fake necklace or jewel could pass for the real thing, it was well worth the added expense, when the genuine article could remain safe under lock and key.

No artificial gem recipes have ever been found among Hollandus' writings, excepting one for ruby which is then crushed up as part of a prescription for the philosopher's stone. It is quite possible that Neri was applying a more general technique from the Dutchman. The basic material for all of Neri's paste gems is a fine lead crystal. The crux of his innovation lay in the form of lead used. Normally, metallic lead sheet was cut into small pieces, and roasted in a kiln such that it would oxidize into powder, but not melt. The powder was then added to the glass melt. In Neri's method the lead was chemically converted into a water-soluble form, which could then be filtered and purified to a much greater extent. The end result was a far better grade of crystal.

In 1697, Jean Haudicquer de Blancourt translated into French and greatly expanded Christopher Merrett's English edition of Neri. Blancourt gave no credit to the Italian for his work, and two years later, when it was translated back into English by Daniel Brown, the connection to Neri was completely lost, but the credit for paste gems remained with Hollandus. In the eighteenth and nineteenth centuries, numerous general encyclopedias of art and craft were published and the so-called 'Hollandus' paste gem recipes turned up many times. Meanwhile, a properly credited French version of L'Arte Vetraria was completed by Holbach in 1752. This edition was more suited to a scientific audience; he faithfully translated the Italian, but also incorporated the full comments of Merrett as well as those of Kunckel who issued his famous German version of Neri in 1679.

For more reading on Neri's artificial gems see Glass as Pasta and on the work of later investigators see Marieke Hendriksen at The Medicine Chest

Cross Pollination

The art of stonework,

from MS Ferguson 67, f. 7r, (1598-1600)

Antonio Neri.

Throughout the Renaissance, Florence, Italy was famous for its artistic output. Names like Donatello, Michelangelo and Giambologna graced the tongues of patrons across Europe. But the secret to the city’s fantastic creativity did not rest solely on individual superstars. The ruling Medici family had found a way to harness the talents of myriad lesser known artisans and use the fruits of their creative labor as a powerful political tool. 

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

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

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

This culture of cross pollination can be seen throughout Antonio Neri's work, in the variety of different glass recipes and also in his knowledge of the ways his glass was to be used. In his 1612 book, L'Arte Vetraria, he says:

Because in order to make vessels and drinking glasses where the glass is thin, you must really load it with a lot of color, but for making large cane for beads not so great a charge of color is necessary. For making thin cane for small beads, you must charge it well with color. In working the glass, you must apportion it with more or less color according to the purpose it must serve.

For lead crystal artisans, he has this advice:

To work lead glass into various drinking glasses or other vessels, or even to draw cane for beadmaking, it is necessary to raise the punty [out of the melt], and to make a gather of glass by turning. Take it out, let it cool somewhat and then work it on a well-cleaned marble [marver]. The marble should be somewhat cool, and well bathed with water before use.

This practice will ensure that the paste of the lead glass does not pull up any of the marble. The glass will always gall marble not bathed in water. Some chips will incorporate into the work, giving it an ugly look. Therefore, frequently flush the marble with fresh water for as long as you are working the glass. Otherwise, all its grace and beauty will be lost.

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

*This post first appeared here on 19 March 2014.

Lead Crystal

Roemer type drinking glass c. 1677,

George Ravenscroft.

The entire fourth part of Antonio Neri's 1612 book L'Arte Vetraria is devoted to the preparation of lead glass, a forerunner of what is now commonly known as lead crystal. This section is unique in the book in that it contains the only instance of the author giving direct advice to glass artists themselves:

"To work lead glass into various drinking glasses or other vessels, or even to draw cane for beadmaking, it is necessary to raise the punty [out of the melt], and to make a gather of glass by turning. Take it out, let it cool somewhat and then work it on a well-cleaned marble [marver]. The marble should be somewhat cool, and well bathed with water before use."

He goes on to describe what might be termed a kind of dance with the glass. As with a human partner, gentle patience is required in learning the boundaries of what can and cannot be done. Ultimately, an artist must come to understand the material's behavior and personality in order to result in a great partnership. For the artist who makes unrealistic demands, glass can be a heartbreaker.  

"This sort of glass, lead glass, is so runny that were it not cooled, and taken up by turning [the punty] to wind a gather, it would be impossible to work. It is so runny that it would not even hold onto the punty, because it is as loose as soup. This arises out of [the fact that] the lead calx causes it to become very fluid."

"Namely, gather the glass little by little, allow it to cool, and work it over marble frequently bathed in water. Furthermore, make sure to keep the pot of glass rather calm, and in a place in the furnace where it will not see too much heat, otherwise it will not be possible to work this glass at all."

The formulation of lead crystal as we know it is a relatively recent development. This is a composition of crushed silica (sand or quartz), potash (potassium carbonates) and lead oxide substituting for calcium to stabilize the composition. It is also true that lead has been added to glass since its invention a few thousand years ago. It is not clear that this addition was always intentional, but a Babylonian tablet of 1700 BCE gives a recipe for pottery glaze that explicitly contains lead. At some point, a discovery showed that small amounts of lead and pigment smeared on glass and fired made stained glass paintings possible. The earliest known examples of colored stained glass windows date to 800-820 (San Vicenzo Abbey excavation in Volturno, Italy.)  In medieval Europe, leading up to Antonio Neri's time, lead glass was used in mosaic tesserae and in artificial gems.

Finally, it is worth noting that Neri's childhood church in Florence, Cestello (now called Santa Maria Maddalena dei Pazzi), was then run by Cistercian monks. It was the Cistercian luminary St. Bernard of Clairvaux who, in the twelfth century, built the first church with large windows, urging, "The soul shall seek the light by following the light."

This post first appeared here 15 November 2013.

Sulfur of Saturn

The Roman Goddess Ops, 'sweet'-heart (and wife)

of Saturn, Peter Paul Rubens c. 1630,

“Abundance (Abundantia).” [1]

Antonio Neri’s 1612 book on glassmaking, L'Arte Vetraria, devotes an entire chapter to making artificial gems. These are made with an especially dense, refractive form of lead glass—what today would be called lead crystal. He made it in small batches, in sealed ceramic vessels; each infused with various metal oxide pigments to give characteristic jewel tone colors.  His secret ingredient for making the finest artificial gems was a material known as "sulfur of Saturn." He writes:

You will have jewels of marvelous beauty in every color, which by far surpass those described above, made with ordinary minium. Because with this true sulfur of Saturn, they will surpass all others by far more than I can write here, as I have seen and made many times in Antwerp.[2]

This "ordinary minium" that he speaks of is one of several oxide forms of lead, also known as 'red lead,' it is bright red or orange in color. As a stable red pigment it was well known to ancient Byzantine and Persian illuminators. [3] It was so popular, in fact, that the word used to describe small intricate pictures 'miniature,' is derived directly from 'minium.' [4] The intricate embellishments in manuscripts ultimately took on the name of the scribes' favorite color.  In glass, minium does not impart red or any other color on its own, but does add 'sparkle' and made Neri's jewels highly refractive to light. 

In the recipe, he uses white vinegar and he reacts it with finely ground minium through a laborious process. The acetic acid in vinegar chemically combines with the minium to form lead acetate, which alchemists called "sugar of Saturn" because it had a distinctively sweet taste (more on that later). [5] Lead (Saturn) could be added to the melt in a number of different forms including acetate, carbonate and various oxides. The heat of the furnace reduces them all and the result is essentially identical glass from any of these sources. The lead acetate has one major advantage that set it apart from the others. Lead acetate is soluble in water and therefore it can easily be purified of contaminants and to a much higher degree. It can be filtered, allowed to stand and decanted after any insoluble impurities settle out.

In other references "sugar of Saturn" and "sulfur of Saturn" are considered synonyms. This is not the case with Neri, for him they are two different substances; the 'sugar' is a precursor for his final product, sulfur of Saturn:

Left in the bottom will be a salt as white as snow, and as sweet as sugar. Repeat the dissolution, and filtering, and evaporation with common water three times. This is the required sugar of Saturn. 

Keep it to calcine in sand in a glass flask or ball in a furnace over a moderated fire for many days. It will further calcine to a color that is much redder than cinnabar, and more finely impalpable than sifted grain flour. This is the required true sulfur of Saturn; purified from the sediment, foulness and blackness that were upon the lead at first. [6]

It would be a reasonable guess that by heating the acetate for "many days" he is reducing it back to minium, its more basic, bright red oxide state, but this time in a greatly purified form.

Unfortunately for his health, in this recipe for sulfur of Saturn, Antonio makes extensive use of heating and evaporation. Even more unfortunate is that in a number of steps he judges the potency of his product by taste. Lead acetate is highly toxic; because it is soluble in water, it enters the bloodstream easily. It attacks the nervous system, accumulates in the bones and can cause organ failure. It is quite likely that by breathing the fumes and tasting crystals of sugar of Saturn, Neri was contributing to his own demise at the relatively young age of thirty-eight. Lead acetate was not the only toxic substance he handled regularly, but it was certainly one of the worst for his health. 

 It does not follow that he was totally ignorant of the risks he was taking. The dangers of heavy metals were recognized from early times. Pliny speaks of the noxious fumes from lead furnaces, and Plutarch opined that lead and mercury mines were "unwholesome and pestilent places." Neri’s own father followed the work of Dioscorides, who wrote that ceruse (lead carbonate), taken internally, could be fatal and that certain sweet wines could adversely affect the abdomen and the nerves.

Ancient Romans discovered that when wine started to turn to vinegar, it could be boiled down in lead lined pots to produce a highly sweet syrup called sapa. A late Roman cookbook made extensive use of sapa, which presumably contained considerable lead acetate. [7] It has been conjectured that  lead laced sapa contributed to poisoning among the Roman aristocracy. While lead acetate is a deadly poison, it is a step too far to imply that it contributed to the fall of the Roman Empire.

[1] Alchemical tradition does provide for an association between the metal lead and the Roman god Saturn. However, there is no such association between 'sugar of Saturn' and either of his consorts Ops or Lua, although Ops, the goddess of abundance (opulence) does rather nicely represent the chemical that made Neri's most opulent artificial gems possible.
[2] Neri 1612, ch. 91.
[3] Chemically, this is Pb3O4, also known as Lead (II,IV) oxide, triplumbic tetroxide. Historically, it was called minium and red lead.
[4] The accepted etymology of ‘miniature’ is from ‘minium,’ but may have been influenced by similar Latin terms such as  minor, minimus, minutus, etc.
[5] Lead acetate comes in two forms; Pb (C2H3O2)4 and Pb (C2H3O2)2, both are toxic; the later variety is soluble in water.
[6] Neri 1612, ch. 91.
[7] “Saba” endures today as a popular grape syrup, albeit without the lead.
* This post forst appeared here on 12 September 2014.

Artificial Gems

Pastes (glass) set in silver openwork (Portugal c. 1750)

Victoria and Albert Museum, London.

Acq. nr. M.68-1962

In many ways, the story of artificial gems traces the story of glass technology itself. From ancient times, when glass could only be produced in very small quantities it was regarded and used as a type of stone that was made through art. Alchemists thought the bright colors produced by metallic pigments in glass were a key to the philosopher's stone, and the transmutation of base metals into gold. As the technical prowess of glassmakers expanded, so did the ability to simulate specific stones, most notably coveted gems. Glass went on to be used as material for utilitarian objects like goblets and as an indispensable part of scientific enquiry. All the while, artificial gems have continued to dazzle us with their beauty. 

In the fifth part of Antonio Neri's 1612 book, he teaches the secrets of making artificial gems "of so much grace, and beauty, that they will surpass the natural stones in everything except hardness." It is not a difficult argument to make that this section alone is responsible for much of the lasting popularity of L'Arte Vetraria. It is easy to see why enterprising artisans would want to make glass imitations that could pass for the real thing. It is also perhaps too tempting to jump to the conclusion that Neri intended his recipes to be used in deception, since there is no evidence whatsoever that this was the case.

Neri gives full credit for his innovative methods in paste gems to Dutch alchemist Isaac Hollandus. Hollandus is an enigmatic figure, whose writings survive, but not much is known of the man, his family, or even if he was living in Neri's time. What is known is that Antonio's dear friend Emmanuel Ximenes was the brother-in-law to Baron Simon Rodriguez d'Evora, a famous diamond dealer and jeweler of choice to royalty throughout Europe. He lived and worked on the same street in Antwerp as Ximenes' palace, only a few steps away from Neri's new temporary home. It was a common request of wealthy patrons to have duplicate jewelry made in paste for travel and security reasons. If a fake necklace or jewel could pass for the real thing, it was well worth the added expense, when the genuine article could remain safe under lock and key.

No artificial gem recipes have ever been found among Hollandus' writings, excepting one for ruby which is then crushed up as part of a prescription for the philosopher's stone. It is quite possible that Neri was applying a more general technique from the Dutchman. The basic material for all of Neri's paste gems is a fine lead crystal. The crux of his innovation lay in the form of lead used. Normally, metallic lead sheet was cut into small pieces, and roasted in a kiln such that it would oxidize into powder, but not melt. The powder was then added to the glass melt. In Neri's method the lead was chemically converted into a water-soluble form, which could then be filtered and purified to a much greater extent. The end result was a far better grade of crystal.


In 1697, Jean Haudicquer de Blancourt translated into French and greatly expanded Christopher Merrett's English edition of Neri. Blancourt gave no credit to the Italian for his work, and two years later, when it was translated back into English by Daniel Brown, the connection to Neri was completely lost, but the credit for paste gems remained with Hollandus. In the eighteenth and nineteenth centuries, numerous general encyclopedias of art and craft were published and the so-called 'Hollandus' paste gem recipes turned up many times. Meanwhile, a properly credited French version of L'Arte Vetraria was completed by Holbach in 1752. This edition was more suited to a scientific audience; he faithfully translated the Italian, but also incorporated the full comments of Merrett as well as those of Kunckel who issued his famous German version of Neri in 1679.

For more reading on Neri's artificial gems see Glass as Pasta and on the work of later investigators see Marieke Hendriksen at The Medicine Chest
*A shorter version of this post appeared here on 16 September 2013.

Cross Pollination

The art of stonework,

from MS Ferguson 67, f. 7r, (1598-1600)

Antonio Neri.

Throughout the Renaissance, Florence, Italy was famous for its artistic output. Names like Donatello, Michelangelo and Giambologna graced the tongues of patrons across Europe. But the secret to the city’s fantastic creativity did not rest solely on individual superstars. The ruling Medici family had found a way to harness the talents of myriad lesser known artisans and use the fruits of their creative labor as a powerful political tool. 

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

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

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

This culture of cross pollination can be seen throughout Antonio Neri's work, in the variety of different glass recipes and also in his knowledge of the ways his glass was to be used. In his 1612 book, L'Arte Vetraria, he says:

Because in order to make vessels and drinking glasses where the glass is thin, you must really load it with a lot of color, but for making large cane for beads not so great a charge of color is necessary. For making thin cane for small beads, you must charge it well with color. In working the glass, you must apportion it with more or less color according to the purpose it must serve.

For lead crystal artisans, he has this advice:

To work lead glass into various drinking glasses or other vessels, or even to draw cane for beadmaking, it is necessary to raise the punty [out of the melt], and to make a gather of glass by turning. Take it out, let it cool somewhat and then work it on a well-cleaned marble [marver]. The marble should be somewhat cool, and well bathed with water before use.

This practice will ensure that the paste of the lead glass does not pull up any of the marble. The glass will always gall marble not bathed in water. Some chips will incorporate into the work, giving it an ugly look. Therefore, frequently flush the marble with fresh water for as long as you are working the glass. Otherwise, all its grace and beauty will be lost.

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

*This post first appeared here on 19 March 2014.