Chalcedony Glass

17th century ribbed bottle,Brescia, Italy.

In hopeful anticipation of flowers, the cusp of spring seems the appropriate time to celebrate Antonio Neri's most colorful creation; chalcedony glass.[1] Through his clever technique, the 17th century glassmaker and alchemist managed to throw every color he knew into one glass pot and come up with, not mud, but the opposite—a swirly rainbow glass that defies verbal description. Somehow, he achieves a balance that blends a full range of colors in a way that seems natural and harmonious. While many glass creations survive from the seventeenth century, none is directly attributable to Neri's glass formulation. But, in my opinion, this piece from Brescia comes close to our alchemist's own description. 

Chalcedony is one of the more exotic varieties of glass described in Antonio Neri's book, L'Arte Vetraria. It is also one of the most labor intensive, exacting recipes and consequently a 'high stakes' risk for losing the entire batch after considerable work. Nevertheless, Neri assures us that the end result is worth the trouble; he describes it as:

Adorned with so many graceful and beautiful areas of undulations and enhanced with the play of diverse, lively, flaming colors.

Chalcedony is a natural mineral, known and admired since antiquity. It occurs in a variety of translucent colors and is most valued when swirls of many different colors are present together in the same piece. In the Roman Empire, it was prized for seals and signet rings; its fine-grained structure allowed intricate carving without fractures. Like many other rare natural materials, it was sometimes supposed to have mystical healing properties. 

Chemically, the mineral chalcedony is identical with quartz or silica, the main ingredient of glass. However, unlike the fabricated substance, the mineral is formed of networks of microscopic interlocking crystals that are responsible for its favorable properties. Small amounts of impurities between the crystal grains cause the swirls of color.

Neri presents three variations of chalcedony glass that span his career as a glassmaker. The first he describes as "the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there." The last was made "in the Flemish city of Antwerp, in January of the year 1611" where he presented "His Excellency, the Prince of Orange with two vessels of chalcedony [glass] which delighted him greatly."

His friend Emmanuel Ximenes was anxious to learn the secrets of this glass as early as July of 1603, when he wrote: 

The details of the last chalcedony [glass], which you promised to send to me, did not come in the letter: but I had to recant by the time I got to the end […] I see and understand, that Your Lordship is not at leisure, but in fact busy at work in the service of Christianity... 

Neri advises that in order to bring out the swirls of color, the glassblower must cool and reheat the piece several times, a process that today is known as 'striking'.

Unfortunately, there is also a dark side to this colorful creation.  It is strongly advised to avoid replication of Neri's chalcedony glass as described in his book of recipes; it contains a cocktail of extremely toxic ingredients. While these are relatively harmless once locked inside the glass, in preparation and especially in the hot molten glass melt, vapors of mercury and arsenic can be deadly. Moderate exposure can be expected to cause neurological and liver damage. (The term "mad as a hatter" comes from the unfortunate side effects of inhaled mercury vapors in the formation of felt hats.) In addition, Neri's extensive uses of strong acid reactions in these preparations make sudden eruptions and severe chemical burns a very real danger.

[1] At least in the northern hemisphere, lets say "autumn colors" in the south.
*This post first appeared here in a slightly different form on 27 September 2013.

Chalcedony Glass

17th century ribbed bottle,Brescia, Italy.

Without a doubt, Antonio Neri's most colorful creation is his chalcedony glass.[1] Through his clever technique, the 17th century glassmaker and alchemist managed to throw every color he knew into one glass pot and come up with, not mud, but the opposite—a swirly rainbow glass that defies verbal description. Somehow, he achieves a balance that blends a full range of colors in a way that seems natural and harmonious. While many glass creations survive from the seventeenth century, none is directly attributable to Neri's glass formulation. But, in my opinion, this piece from Brescia comes close to our alchemist's own description. 

Chalcedony is one of the more exotic varieties of glass described in Antonio Neri's book, L'Arte Vetraria. It is also one of the most labor intensive, exacting recipes and consequently a 'high stakes' risk for losing the entire batch after considerable work. Nevertheless, Neri assures us that the end result is worth the trouble; he describes it as:

Adorned with so many graceful and beautiful areas of undulations and enhanced with the play of diverse, lively, flaming colors.

Chalcedony is a natural mineral, known and admired since antiquity. It occurs in a variety of translucent colors and is most valued when swirls of many different colors are present together in the same piece. In the Roman Empire, it was prized for seals and signet rings; its fine-grained structure allowed intricate carving without fractures. Like many other rare natural materials, it was sometimes supposed to have mystical healing properties. 

Chemically, the mineral chalcedony is identical with quartz or silica, the main ingredient of glass. However, unlike the fabricated substance, the mineral is formed of networks of microscopic interlocking crystals that are responsible for its favorable properties. Small amounts of impurities between the crystal grains cause the swirls of color.

Neri presents three variations of chalcedony glass that span his career as a glassmaker. The first he describes as "the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there." The last was made "in the Flemish city of Antwerp, in January of the year 1611" where he presented "His Excellency, the Prince of Orange with two vessels of chalcedony [glass] which delighted him greatly."

His friend Emmanuel Ximenes was anxious to learn the secrets of this glass as early as July of 1603, when he wrote: 

The details of the last chalcedony [glass], which you promised to send to me, did not come in the letter: but I had to recant by the time I got to the end […] I see and understand, that Your Lordship is not at leisure, but in fact busy at work in the service of Christianity... 

Neri advises that in order to bring out the swirls of color, the glassblower must cool and reheat the piece several times, a process that today is known as 'striking'.

Unfortunately, there is also a dark side to this colorful creation.  It is strongly advised to avoid replication of Neri's chalcedony glass as described in his book of recipes; it contains a cocktail of extremely toxic ingredients. While these are relatively harmless once locked inside the glass, in preparation and especially in the hot molten glass melt, vapors of mercury and arsenic can be deadly. Moderate exposure can be expected to cause neurological and liver damage. (The term "mad as a hatter" comes from the unfortunate side effects of inhaled mercury vapors in the formation of felt hats.) In addition, Neri's extensive uses of strong acid reactions in these preparations make sudden eruptions and severe chemical burns a very real danger.

[1] At least in the northern hemisphere, lets say "autumn colors" in the south.
*This post first appeared here in a slightly different form on 27 September 2013.

Deadly Fumes

Memento mori, 1605.
Nikolaus Alexander  Mair von Landshut.

17th century glassmaker and alchemist Antonio Neri handled very dangerous materials on a daily basis. He used strong acids, which if splattered could easily burn flesh, or cause blindness. He handled poisonous compounds containing arsenic, mercury and lead. If ingested, or inhaled as fumes these materials caused progressive, irreversible damage to internal organs and especially to the nervous system. There is no question that Neri did take chances with his health, but he was not naive. He knew very well many of the potential dangers and others he could well imagine. In chapter 74 of his book L'Arte Vetraria, he describes a way to tint rock crystal with beautiful colors. He wrote: 

Take orpiment of that really tawny orange-yellow color and pulverize 2 ounces of this along with 2 ounces of powdered crystalline arsenic, 1 ounce of pulverized crude antimony, and 1 ounce of sal ammoniac. […] Perform this entire operation under a large chimney to draw the fumes out of the room. These fumes are not only harmful but also quite deadly. Return to see if the coals have died down, because for the work to come out nicely, they must be burning well and full. For the remainder, leave and let the fire run its course with no one in the room with the work, for it is dangerous; the harsh materials will smoke quite a bit. Leave it to finish all fuming by itself and then extinguish the fire and spread the coals.[1]

In the spring of 1603, Neri was working in Pisa and became seriously ill. The specific cause and symptoms of his ailment are not known. He could have been harmed by one of his own experiments, or just as easily fallen prey to an infection or one of many other maladies prevalent in the early seventeenth century. He postponed his planned visit to Antwerp in order to recuperate. Finally, on 2 May 1603, his friend Emmanuel Ximenes wrote: "Praise God that your indisposition has ended ... if the Pisan air is suited to your recovery then do not change it." [2]

In the winter of 1603-4 Neri embarked on what would become a seven-year-long visit to his friend's palace in Antwerp. There, he would learn many new techniques, and ultimately have special glass vessels made and presented to Philip William, Prince of Orange. Upon his return to Tuscany in 1611, he sat down to write the book for which he is most remembered, L'Arte Vetraria. Two years after publication, in 1614, the priest would be dead. According to the only known account, printed over two centuries later by Francesco Inghirami.

Meanwhile, Neri became gravely ill, so he called the prince to come to him, having the promised the secret [of the philosophers stone]. But the Medici, who was in the countryside, took too much time; the patient died before the prince could be with him. Don Antonio was not quieted and he questioned all of Neri’s friends to see if he could find the information, but his efforts were in vain, as they should be in so groundless a science, although Giacinto Salducci [sic.] said that he had seen great things, specifically a powder that fixed mercury into gold. [3]

[1] Neri 1612, ch. 74.
[2] Ximenes 1601–11, also see Zecchin 1987–89, v. 1, pp. 165–169.
[3] Inghirami 1841–44,v. 13, pp. 457–458 probably based on Targioni-Tozzetti  189.

This post first appeared here in a slightly shorter form on 30 October 2013.

Chalcedony Glass

17th century ribbed bottle,Brescia, Italy.

In hopeful anticipation of flowers, the cusp of spring seems the appropriate time to celebrate Antonio Neri's most colorful creation; chalcedony glass.[1] Through his clever technique, the 17th century glassmaker and alchemist managed to throw every color he knew into one glass pot and come up with, not mud, but the opposite—a swirly rainbow glass that defies verbal description. Somehow, he achieves a balance that blends a full range of colors in a way that seems natural and harmonious. While many glass creations survive from the seventeenth century, none is directly attributable to Neri's glass formulation. But, in my opinion, this piece from Brescia comes close to our alchemist's own description. 

Chalcedony is one of the more exotic varieties of glass described in Antonio Neri's book, L'Arte Vetraria. It is also one of the most labor intensive, exacting recipes and consequently a 'high stakes' risk for losing the entire batch after considerable work. Nevertheless, Neri assures us that the end result is worth the trouble; he describes it as:

Adorned with so many graceful and beautiful areas of undulations and enhanced with the play of diverse, lively, flaming colors.

Chalcedony is a natural mineral, known and admired since antiquity. It occurs in a variety of translucent colors and is most valued when swirls of many different colors are present together in the same piece. In the Roman Empire, it was prized for seals and signet rings; its fine-grained structure allowed intricate carving without fractures. Like many other rare natural materials, it was sometimes supposed to have mystical healing properties. 

Chemically, the mineral chalcedony is identical with quartz or silica, the main ingredient of glass. However, unlike the fabricated substance, the mineral is formed of networks of microscopic interlocking crystals that are responsible for its favorable properties. Small amounts of impurities between the crystal grains cause the swirls of color.

Neri presents three variations of chalcedony glass that span his career as a glassmaker. The first he describes as "the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there." The last was made "in the Flemish city of Antwerp, in January of the year 1611" where he presented "His Excellency, the Prince of Orange with two vessels of chalcedony [glass] which delighted him greatly."

His friend Emmanuel Ximenes was anxious to learn the secrets of this glass as early as July of 1603, when he wrote: 

The details of the last chalcedony [glass], which you promised to send to me, did not come in the letter: but I had to recant by the time I got to the end […] I see and understand, that Your Lordship is not at leisure, but in fact busy at work in the service of Christianity... 

Neri advises that in order to bring out the swirls of color, the glassblower must cool and reheat the piece several times, a process that today is known as 'striking'.

Unfortunately, there is also a dark side to this colorful creation.  It is strongly advised to avoid replication of Neri's chalcedony glass as described in his book of recipes; it contains a cocktail of extremely toxic ingredients. While these are relatively harmless once locked inside the glass, in preparation and especially in the hot molten glass melt, vapors of mercury and arsenic can be deadly. Moderate exposure can be expected to cause neurological and liver damage. (The term "mad as a hatter" comes from the unfortunate side effects of inhaled mercury vapors in the formation of felt hats.) In addition, Neri's extensive uses of strong acid reactions in these preparations make sudden eruptions and severe chemical burns a very real danger.

[1] At least in the northern hemisphere, lets say "autumn colors" in the south.
*This post first appeared here in a slightly different form on 27 September 2013.

Deadly Fumes

Memento mori, 1605.
Nikolaus Alexander  Mair von Landshut.

17th century glassmaker and alchemist Antonio Neri handled very dangerous materials on a daily basis. He used strong acids, which if splattered could easily burn flesh, or cause blindness. He handled poisonous compounds containing arsenic, mercury and lead. If ingested, or inhaled as fumes these materials caused progressive, irreversible damage to internal organs and especially to the nervous system. There is no question that Neri did take chances with his health, but he was not naive. He knew very well many of the potential dangers and others he could well imagine. In chapter 74 of his book L'Arte Vetraria, he describes a way to tint rock crystal with beautiful colors. He wrote: 

Take orpiment of that really tawny orange-yellow color and pulverize 2 ounces of this along with 2 ounces of powdered crystalline arsenic, 1 ounce of pulverized crude antimony, and 1 ounce of sal ammoniac. […] Perform this entire operation under a large chimney to draw the fumes out of the room. These fumes are not only harmful but also quite deadly. Return to see if the coals have died down, because for the work to come out nicely, they must be burning well and full. For the remainder, leave and let the fire run its course with no one in the room with the work, for it is dangerous; the harsh materials will smoke quite a bit. Leave it to finish all fuming by itself and then extinguish the fire and spread the coals.[1]

In the spring of 1603, Neri was working in Pisa and became seriously ill. The specific cause and symptoms of his ailment are not known. He could have been harmed by one of his own experiments, or just as easily fallen prey to an infection or one of many other maladies prevalent in the early seventeenth century. He postponed his planned visit to Antwerp in order to recuperate. Finally, on 2 May 1603, his friend Emmanuel Ximenes wrote: "Praise God that your indisposition has ended ... if the Pisan air is suited to your recovery then do not change it." [2]

In the winter of 1603-4 Neri embarked on what would become a seven-year-long visit to his friend's palace in Antwerp. There, he would learn many new techniques, and ultimately have special glass vessels made and presented to Philip William, Prince of Orange. Upon his return to Tuscany in 1611, he sat down to write the book for which he is most remembered, L'Arte Vetraria. Two years after publication, in 1614, the priest would be dead. According to the only known account, printed over two centuries later by Francesco Inghirami.

Meanwhile, Neri became gravely ill, so he called the prince to come to him, having the promised the secret [of the philosophers stone]. But the Medici, who was in the countryside, took too much time; the patient died before the prince could be with him. Don Antonio was not quieted and he questioned all of Neri’s friends to see if he could find the information, but his efforts were in vain, as they should be in so groundless a science, although Giacinto Salducci [sic.] said that he had seen great things, specifically a powder that fixed mercury into gold. [3]

[1] Neri 1612, ch. 74.
[2] Ximenes 1601–11, also see Zecchin 1987–89, v. 1, pp. 165–169.
[3] Inghirami 1841–44,v. 13, pp. 457–458 probably based on Targioni-Tozzetti  189.

This post first appeared here in a slightly shorter form on 30 October 2013.

Chalcedony Glass

17th century ribbed bottle,Brescia, Italy.

In hopeful anticipation of flowers, the cusp of spring seems the appropriate time to celebrate Antonio Neri's most colorful creation; chalcedony glass.[1] Through his clever technique, the 17th century glassmaker and alchemist managed to throw every color he knew into one glass pot and come up with, not mud, but the opposite—a swirly rainbow glass that defies verbal description. Somehow, he achieves a balance that blends a full range of colors in a way that seems natural and harmonious. While many glass creations survive from the seventeenth century, none is directly attributable to Neri's glass formulation. But, in my opinion, this piece from Brescia comes close to our alchemist's own description. 

Chalcedony is one of the more exotic varieties of glass described in Antonio Neri's book, L'Arte Vetraria. It is also one of the most labor intensive, exacting recipes and consequently a 'high stakes' risk for losing the entire batch after considerable work. Nevertheless, Neri assures us that the end result is worth the trouble; he describes it as:

Adorned with so many graceful and beautiful areas of undulations and enhanced with the play of diverse, lively, flaming colors.

Chalcedony is a natural mineral, known and admired since antiquity. It occurs in a variety of translucent colors and is most valued when swirls of many different colors are present together in the same piece. In the Roman Empire, it was prized for seals and signet rings; its fine-grained structure allowed intricate carving without fractures. Like many other rare natural materials, it was sometimes supposed to have mystical healing properties. 

Chemically, the mineral chalcedony is identical with quartz or silica, the main ingredient of glass. However, unlike the fabricated substance, the mineral is formed of networks of microscopic interlocking crystals that are responsible for its favorable properties. Small amounts of impurities between the crystal grains cause the swirls of color.

Neri presents three variations of chalcedony glass that span his career as a glassmaker. The first he describes as "the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there." The last was made "in the Flemish city of Antwerp, in January of the year 1611" where he presented "His Excellency, the Prince of Orange with two vessels of chalcedony [glass] which delighted him greatly."

His friend Emmanuel Ximenes was anxious to learn the secrets of this glass as early as July of 1603, when he wrote: 

The details of the last chalcedony [glass], which you promised to send to me, did not come in the letter: but I had to recant by the time I got to the end […] I see and understand, that Your Lordship is not at leisure, but in fact busy at work in the service of Christianity... 

Neri advises that in order to bring out the swirls of color, the glassblower must cool and reheat the piece several times, a process that today is known as 'striking'.

Unfortunately, there is also a dark side to this colorful creation.  It is strongly advised to avoid replication of Neri's chalcedony glass as described in his book of recipes; it contains a cocktail of extremely toxic ingredients. While these are relatively harmless once locked inside the glass, in preparation and especially in the hot molten glass melt, vapors of mercury and arsenic can be deadly. Moderate exposure can be expected to cause neurological and liver damage. (The term "mad as a hatter" comes from the unfortunate side effects of inhaled mercury vapors in the formation of felt hats.) In addition, Neri's extensive uses of strong acid reactions in these preparations make sudden eruptions and severe chemical burns a very real danger.

[1] At least in the northern hemisphere, lets say "autumn colors" in the south.
*This post first appeared here in a slightly different form on 27 September 2013.

Deadly Fumes

Memento mori, 1605.
Nikolaus Alexander  Mair von Landshut.

17th century glassmaker and alchemist Antonio Neri handled very dangerous materials on a daily basis. He used strong acids, which if splattered could easily burn flesh, or cause blindness. He handled poisonous compounds containing arsenic, mercury and lead. If ingested, or inhaled as fumes these materials caused progressive, irreversible damage to internal organs and especially to the nervous system. There is no question that Neri did take chances with his health, but he was not naive. He knew very well many of the potential dangers and others he could well imagine. In chapter 74 of his book L'Arte Vetraria, he describes a way to tint rock crystal with beautiful colors. He wrote: 

Take orpiment of that really tawny orange-yellow color and pulverize 2 ounces of this along with 2 ounces of powdered crystalline arsenic, 1 ounce of pulverized crude antimony, and 1 ounce of sal ammoniac. […] Perform this entire operation under a large chimney to draw the fumes out of the room. These fumes are not only harmful but also quite deadly. Return to see if the coals have died down, because for the work to come out nicely, they must be burning well and full. For the remainder, leave and let the fire run its course with no one in the room with the work, for it is dangerous; the harsh materials will smoke quite a bit. Leave it to finish all fuming by itself and then extinguish the fire and spread the coals.[1]

In the spring of 1603, Neri was working in Pisa and became seriously ill. The specific cause and symptoms of his ailment are not known. He could have been harmed by one of his own experiments, or just as easily fallen prey to an infection or one of many other maladies prevalent in the early seventeenth century. He postponed his planned visit to Antwerp in order to recuperate. Finally, on 2 May 1603, his friend Emmanuel Ximenes wrote: "Praise God that your indisposition has ended ... if the Pisan air is suited to your recovery then do not change it." [2]

In the winter of 1603-4 Neri embarked on what would become a seven-year-long visit to his friend's palace in Antwerp. There, he would learn many new techniques, and ultimately have special glass vessels made and presented to Philip William, Prince of Orange. Upon his return to Tuscany in 1611, he sat down to write the book for which he is most remembered, L'Arte Vetraria. Two years after publication, in 1614, the priest would be dead. According to the only known account, printed over two centuries later by Francesco Inghirami.

Meanwhile, Neri became gravely ill, so he called the prince to come to him, having the promised the secret [of the philosophers stone]. But the Medici, who was in the countryside, took too much time; the patient died before the prince could be with him. Don Antonio was not quieted and he questioned all of Neri’s friends to see if he could find the information, but his efforts were in vain, as they should be in so groundless a science, although Giacinto Salducci [sic.] said that he had seen great things, specifically a powder that fixed mercury into gold. [3]

[1] Neri 1612, ch. 74.
[2] Ximenes 1601–11, also see Zecchin 1987–89, v. 1, pp. 165–169.
[3] Inghirami 1841–44,v. 13, pp. 457–458 probably based on Targioni-Tozzetti  189.

This post first appeared here in a slightly shorter form on 30 October 2013.

Chalcedony Glass

17th century ribbed bottle,Brescia, Italy.

In hopeful anticipation of colorful flowers, the cusp of spring, seems the appropriate time to celebrate Antonio Neri's most colorful creation; chalcedony glass.[1] Through his clever technique, Neri managed to throw every color he knew into one glass pot and come up with, not mud, but the opposite—a swirly rainbow glass that defies verbal description. Somehow, he achieves a balance that blends a full range of colors in a way that seems natural and harmonious. While many glass creations survive from the seventeenth century, none is directly attributable to Neri's glass formulation. But, in my opinion, this piece from Brescia comes close to our alchemist's own description. 

Chalcedony is one of the more exotic varieties of glass described in Antonio Neri's book, L'Arte Vetraria. It is also one of the most labor intensive, exacting recipes and consequently a 'high stakes' risk for losing the entire batch after considerable work. Nevertheless, Neri assures us that the end result is worth the trouble; he describes it as:

Adorned with so many graceful and beautiful areas of undulations and enhanced with the play of diverse, lively, flaming colors.

Chalcedony is a natural mineral, known and admired since antiquity. It occurs in a variety of translucent colors and is most valued when swirls of many different colors are present together in the same piece. In the Roman Empire, it was prized for seals and signet rings; its fine-grained structure allowed intricate carving without fractures. Like many other rare natural materials, it was sometimes supposed to have mystical healing properties. 

Chemically, the mineral chalcedony is identical with quartz or silica, the main ingredient of glass. However, unlike the fabricated substance, the mineral is formed of networks of microscopic interlocking crystals that are responsible for its favorable properties. Small amounts of impurities between the crystal grains cause the swirls of color.

Neri presents three variations of chalcedony glass that span his career as a glassmaker. The first he describes as "the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there." The last was made "in the Flemish city of Antwerp, in January of the year 1611" where he presented "His Excellency, the Prince of Orange with two vessels of chalcedony [glass] which delighted him greatly."

His friend Emmanuel Ximenes was anxious to learn the secrets of this glass as early as July of 1603, when he wrote: 

The details of the last chalcedony [glass], which you promised to send to me, did not come in the letter: but I had to recant by the time I got to the end […] I see and understand, that Your Lordship is not at leisure, but in fact busy at work in the service of Christianity... 

Neri advises that in order to bring out the swirls of color, the glassblower must cool and reheat the piece several times, a process that today is known as 'striking'.

Unfortunately, there is also a dark side to this colorful creation.  It is strongly advised to avoid replication of Neri's chalcedony glass as described in his book of recipes; it contains a cocktail of extremely toxic ingredients. While these are relatively harmless once locked inside the glass, in preparation and especially in the hot molten glass melt, vapors of mercury and arsenic can be deadly. Moderate exposure can be expected to cause neurological and liver damage. (The term "mad as a hatter" comes from the unfortunate side effects of inhaled mercury vapors in the formation of felt hats.) In addition, Neri's extensive uses of strong acid reactions in these preparations make sudden eruptions and severe chemical burns a very real danger.

[1] At least in the northern hemisphere, lets say "autumn colors" in the south.
*This post first appeared here in a slightly different form on 27 September 2013.

Deadly Fumes

Memento mori, 1605.
Nikolaus Alexander  Mair von Landshut.

17th century glassmaker and alchemist Antonio Neri handled very dangerous materials on a daily basis. He used strong acids, which if splattered could easily burn flesh, or cause blindness. He handled poisonous compounds containing arsenic, mercury and lead. If ingested, or inhaled as fumes these materials caused progressive, irreversible damage to internal organs and especially to the nervous system. There is no question that Neri did take chances with his health, but he was not naive. He knew very well many of the potential dangers and others he could well imagine. In chapter 74 of his book L'Arte Vetraria, he describes a way to tint rock crystal with beautiful colors. He wrote: 

Take orpiment of that really tawny orange-yellow color and pulverize 2 ounces of this along with 2 ounces of powdered crystalline arsenic, 1 ounce of pulverized crude antimony, and 1 ounce of sal ammoniac. […] Perform this entire operation under a large chimney to draw the fumes out of the room. These fumes are not only harmful but also quite deadly. Return to see if the coals have died down, because for the work to come out nicely, they must be burning well and full. For the remainder, leave and let the fire run its course with no one in the room with the work, for it is dangerous; the harsh materials will smoke quite a bit. Leave it to finish all fuming by itself and then extinguish the fire and spread the coals.[1]

In the spring of 1603, Neri was working in Pisa and became seriously ill. The specific cause and symptoms of his ailment are not known. He could have been harmed by one of his own experiments, or just as easily fallen prey to an infection or one of many other maladies prevalent in the early seventeenth century. He postponed his planned visit to Antwerp in order to recuperate. Finally, on 2 May 1603, his friend Emmanuel Ximenes wrote: "Praise God that your indisposition has ended ... if the Pisan air is suited to your recovery then do not change it." [2]

In the winter of 1603-4 Neri embarked on what would become a seven-year-long visit to his friend's palace in Antwerp. There, he would learn many new techniques, and ultimately have special glass vessels made and presented to Philip William, Prince of Orange. Upon his return to Tuscany in 1611, he sat down to write the book for which he is most remembered, L'Arte Vetraria. Two years after publication, in 1614, the priest would be dead. According to the only known account, printed over two centuries later by Francesco Inghirami.

Meanwhile, Neri became gravely ill, so he called the prince to come to him, having the promised the secret [of the philosophers stone]. But the Medici, who was in the countryside, took too much time; the patient died before the prince could be with him. Don Antonio was not quieted and he questioned all of Neri’s friends to see if he could find the information, but his efforts were in vain, as they should be in so groundless a science, although Giacinto Salducci [sic.] said that he had seen great things, specifically a powder that fixed mercury into gold. [3]

[1] Neri 1612, ch. 74.
[2] Ximenes 1601–11, also see Zecchin 1987–89, v. 1, pp. 165–169.
[3] Inghirami 1841–44,v. 13, pp. 457–458 probably based on Targioni-Tozzetti  189.

This post first appeared here in a slightly shorter form on 30 October 2013.

Chalcedony Glass

17th century ribbed bottle,Brescia, Italy.

In hopeful anticipation of colorful flowers, the cusp of spring, seems the appropriate time to celebrate Antonio Neri's most colorful creation; chalcedony glass.[1] Through his clever technique, Neri managed to throw every color he knew into one glass pot and come up with, not mud, but the opposite—a swirly rainbow glass that defies verbal description. Somehow, he achieves a balance that blends a full range of colors in a way that seems natural and harmonious. While many glass creations survive from the seventeenth century, none is directly attributable to Neri's glass formulation. But, in my opinion, this piece from Brescia comes close to our alchemist's own description. 

Chalcedony is one of the more exotic varieties of glass described in Antonio Neri's book, L'Arte Vetraria. It is also one of the most labor intensive, exacting recipes and consequently a 'high stakes' risk for losing the entire batch after considerable work. Nevertheless, Neri assures us that the end result is worth the trouble; he describes it as:

Adorned with so many graceful and beautiful areas of undulations and enhanced with the play of diverse, lively, flaming colors.

Chalcedony is a natural mineral, known and admired since antiquity. It occurs in a variety of translucent colors and is most valued when swirls of many different colors are present together in the same piece. In the Roman Empire, it was prized for seals and signet rings; its fine-grained structure allowed intricate carving without fractures. Like many other rare natural materials, it was sometimes supposed to have mystical healing properties. 

Chemically, the mineral chalcedony is identical with quartz or silica, the main ingredient of glass. However, unlike the fabricated substance, the mineral is formed of networks of microscopic interlocking crystals that are responsible for its favorable properties. Small amounts of impurities between the crystal grains cause the swirls of color.

Neri presents three variations of chalcedony glass that span his career as a glassmaker. The first he describes as "the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there." The last was made "in the Flemish city of Antwerp, in January of the year 1611" where he presented "His Excellency, the Prince of Orange with two vessels of chalcedony [glass] which delighted him greatly."

His friend Emmanuel Ximenes was anxious to learn the secrets of this glass as early as July of 1603, when he wrote: 

The details of the last chalcedony [glass], which you promised to send to me, did not come in the letter: but I had to recant by the time I got to the end […] I see and understand, that Your Lordship is not at leisure, but in fact busy at work in the service of Christianity... 

Neri advises that in order to bring out the swirls of color, the glassblower must cool and reheat the piece several times, a process that today is known as 'striking'.

Unfortunately, there is also a dark side to this colorful creation.  It is strongly advised to avoid replication of Neri's chalcedony glass as described in his book of recipes; it contains a cocktail of extremely toxic ingredients. While these are relatively harmless once locked inside the glass, in preparation and especially in the hot molten glass melt, vapors of mercury and arsenic can be deadly. Moderate exposure can be expected to cause neurological and liver damage. (The term "mad as a hatter" comes from the unfortunate side effects of inhaled mercury vapors in the formation of felt hats.) In addition, Neri's extensive uses of strong acid reactions in these preparations make sudden eruptions and severe chemical burns a very real danger.

[1] At least in the northern hemisphere, lets say "autumn colors" in the south.
*This post first appeared here in a slightly different form on 27 September 2013.

Deadly Fumes

  Memento mori, 1605. 
Nikolaus Alexander  Mair von Landshut.

17th century glassmaker and alchemist Antonio Neri handled very dangerous materials on a daily basis. He used strong acids, which if splattered could easily burn flesh, or cause blindness. He handled poisonous compounds containing arsenic, mercury and lead. If ingested, or inhaled as fumes these materials caused progressive, irreversible damage to internal organs and especially to the nervous system. There is no question that Neri did take chances with his health, but he was not naive. He knew very well many of the potential dangers and others he could well imagine. In chapter 74 of his book L'Arte Vetraria, he describes a way to tint rock crystal with beautiful colors. He wrote: 

Take orpiment of that really tawny orange-yellow color and pulverize 2 ounces of this along with 2 ounces of powdered crystalline arsenic, 1 ounce of pulverized crude antimony, and 1 ounce of sal ammoniac. […] Perform this entire operation under a large chimney to draw the fumes out of the room. These fumes are not only harmful but also quite deadly. Return to see if the coals have died down, because for the work to come out nicely, they must be burning well and full. For the remainder, leave and let the fire run its course with no one in the room with the work, for it is dangerous; the harsh materials will smoke quite a bit. Leave it to finish all fuming by itself and then extinguish the fire and spread the coals.[1]

In the spring of 1603, Neri was working in Pisa and became seriously ill. The specific cause and symptoms of his ailment are not known. He could have been harmed by one of his own experiments, or just as easily fallen prey to an infection or one of many other maladies prevalent in the early seventeenth century. He postponed his planned visit to Antwerp in order to recuperate. Finally, on 2 May 1603, his friend Emmanuel Ximenes wrote: "Praise God that your indisposition has ended ... if the Pisan air is suited to your recovery then do not change it." [2]

In the winter of 1603-4 Neri embarked on what would become a seven-year-long visit to his friend's palace in Antwerp. There, he would learn many new techniques, and ultimately have special glass vessels made and presented to Philip William, Prince of Orange. Upon his return to Tuscany in 1611, he sat down to write the book for which he is most remembered, L'Arte Vetraria. Two years after publication, in 1614, the priest would be dead. According to the only known account, printed over two centuries later by Francesco Inghirami.

Meanwhile, Neri became gravely ill, so he called the prince to come to him, having the promised the secret [of the philosophers stone]. But the Medici, who was in the countryside, took too much time; the patient died before the prince could be with him. Don Antonio was not quieted and he questioned all of Neri’s friends to see if he could find the information, but his efforts were in vain, as they should be in so groundless a science, although Giacinto Salducci [sic.] said that he had seen great things, specifically a powder that fixed mercury into gold. [3]

[1] Neri 1612, ch. 74.
[2] Ximenes 1601–11, also see Zecchin 1987–89, v. 1, pp. 165–169.
[3] Inghirami 1841–44,v. 13, pp. 457–458 probably based on Targioni-Tozzetti  189.

This post first appeared here in a slightly shorter form on 30 October 2013.

Chalcedony Glass

17th century ribbed bottle,Brescia, Italy.

After a long, brutal, winter, New England might possibly be starting to thaw. On the cusp of April, in hopeful anticipation of spring flowers, it seems appropriate to celebrate Antonio Neri's most colorful creation; chalcedony glass. Through his clever technique, Neri was able to throw every color he knew into one glass pot and come up with, not mud, but the opposite—a swirly rainbow glass that defies verbal description. Somehow, he achieves a balance that blends a full range of colors in a way that seems natural and harmonious. While many glass creations survive from the seventeenth century, none is directly attributable to Neri's glass formulation. But, in my opinion, this piece from Brescia comes close to our alchemist's own description. 

Chalcedony is one of the more exotic varieties of glass described in Antonio Neri's book, L'Arte Vetraria. It is also one of the most labor intensive, exacting recipes and consequently a 'high stakes' risk for losing the entire batch after considerable work. Nevertheless, Neri assures us that the end result is worth the trouble; he describes it as:

Adorned with so many graceful and beautiful areas of undulations and enhanced with the play of diverse, lively, flaming colors.

Chalcedony is a natural mineral, known and admired since antiquity. It occurs in a variety of translucent colors and is most valued when swirls of many different colors are present together in the same piece. In the Roman Empire, it was prized for seals and signet rings; its fine-grained structure allowed intricate carving without fractures. Like many other rare natural materials, it was sometimes supposed to have mystical healing properties. 

Chemically, the mineral chalcedony is identical with quartz or silica, the main ingredient of glass. However, unlike the fabricated substance, the mineral is formed of networks of microscopic interlocking crystals that are responsible for its favorable properties. Small amounts of impurities between the crystal grains cause the swirls of color.

Neri presents three variations of chalcedony glass that span his career as a glassmaker. The first he describes as "the way that I made chalcedony in the year 1601, in Florence at the Casino, in the glass furnace there." The last was made "in the Flemish city of Antwerp, in January of the year 1611" where he presented "His Excellency, the Prince of Orange with two vessels of chalcedony [glass] which delighted him greatly."

His friend Emmanuel Ximenes was anxious to learn the secrets of this glass as early as July of 1603, when he wrote: 

The details of the last chalcedony [glass], which you promised to send to me, did not come in the letter: but I had to recant by the time I got to the end […] I see and understand, that Your Lordship is not at leisure, but in fact busy at work in the service of Christianity... 

Neri advises that in order to bring out the swirls of color, the glassblower must cool and reheat the piece several times, a process that today is known as 'striking'.

Unfortunately, there is also a dark side to this colorful creation.  It is strongly advised to avoid replication of Neri's chalcedony glass as described in his book of recipes; it contains a cocktail of extremely toxic ingredients. While these are relatively harmless once locked inside the glass, in preparation and especially in the hot molten glass melt, vapors of mercury and arsenic can be deadly. Moderate exposure can be expected to cause neurological and liver damage. (The term "mad as a hatter" comes from the unfortunate side effects of inhaled mercury vapors in the formation of felt hats.) In addition, Neri's extensive uses of strong acid reactions in these preparations make sudden eruptions and severe chemical burns a very real danger.

*This post first appeared here in a slightly different form on 27 September 2013.

Deadly Fumes Reprise

Antonio Neri handled very dangerous materials on a daily basis. He used strong acids, which if splattered could easily burn flesh, or cause blindness. He handled poisonous compounds containing arsenic, mercury and lead. If ingested, or inhaled as fumes these materials caused progressive, irreversible damage to internal organs and especially to the nervous system. There is no question that Neri did take chances with his health, but he was not naive. He knew very well many of the potential dangers and others he could well imagine. In chapter 74 of his book L'Arte Vetraria, he describes a way to tint rock crystal with beautiful colors. He wrote: 

Take orpiment of that really tawny orange-yellow color and pulverize 2 ounces of this along with 2 ounces of powdered crystalline arsenic, 1 ounce of pulverized crude antimony, and 1 ounce of sal ammoniac. […] Perform this entire operation under a large chimney to draw the fumes out of the room. These fumes are not only harmful but also quite deadly. Return to see if the coals have died down, because for the work to come out nicely, they must be burning well and full. For the remainder, leave and let the fire run its course with no one in the room with the work, for it is dangerous; the harsh materials will smoke quite a bit. Leave it to finish all fuming by itself and then extinguish the fire and spread the coals.[1]

In the spring of 1603, Neri was working in Pisa and became seriously ill. The specific cause and symptoms of his ailment are not known. He could have been harmed by one of his own experiments, or just as easily fallen prey to an infection or one of many other maladies prevalent in the early seventeenth century. He postponed his planned visit to Antwerp in order to recuperate. Finally, on 2 May 1603, his friend Emmanuel Ximenes wrote: "Praise God that your indisposition has ended ... if the Pisan air is suited to your recovery then do not change it." [2]

In the winter of 1603-4 Neri embarked on what would become a seven-year-long visit to his friend's palace in Antwerp. There, he would learn many new techniques, and ultimately have special glass vessels made and presented to Philip William, Prince of Orange. Upon his return to Tuscany in 1611, he sat down to write the book for which he is most remembered, L'Arte Vetraria. Two years after publication, in 1614, the priest would be dead. According to the only known account, printed over two centuries later by Francesco Inghirami.

Meanwhile, Neri became gravely ill, so he called the prince to come to him, having the promised the secret [of the philosophers stone]. But the Medici, who was in the countryside, took too much time; the patient died before the prince could be with him. Don Antonio was not quieted and he questioned all of Neri’s friends to see if he could find the information, but his efforts were in vain, as they should be in so groundless a science, although Giacinto Salducci [sic.] said that he had seen great things, specifically a powder that fixed mercury into gold. [3]

[1] Neri 1612, ch. 74.
[2] Ximenes 1601–11, also see Zecchin 1987–89, v. 1, pp. 165–169.
[3] Inghirami 1841–44,v. 13, pp. 457–458 probably based on Targioni-Tozzetti  189.

This post first appeared here in a slightly shorter form on 30 October 2013.

Deadly Fumes

Antonio Neri handled very dangerous materials on a daily basis. He used strong acids, which if splattered could easily burn flesh, or cause blindness. He handled poisonous compounds containing arsenic, mercury and lead. If ingested, or inhaled as fumes these materials caused progressive, irreversible damage to internal organs and especially to the nervous system. There is no question that Neri did take chances with his health, but he was not naive. He knew very well many of the potential dangers and others he could well imagine. In chapter 74 of his book L'Arte Vetraria, he describes a way to tint rock crystal with beautiful colors. He wrote:

Take orpiment of that really tawny orange-yellow color and pulverize 2 ounces of this along with 2 ounces of powdered crystalline arsenic, 1 ounce of pulverized crude antimony, and 1 ounce of sal ammoniac. […] Perform this entire operation under a large chimney to draw the fumes out of the room. These fumes are not only harmful but also quite deadly. Return to see if the coals have died down, because for the work to come out nicely, they must be burning well and full. For the remainder, leave and let the fire run its course with no one in the room with the work, for it is dangerous; the harsh materials will smoke quite a bit. Leave it to finish all fuming by itself and then extinguish the fire and spread the coals.

In the spring of 1603, Neri was working in Pisa and became seriously ill. The specific cause and symptoms of his ailment are not known. He could have been harmed by one of his own experiments, or just as easily fallen prey to an infection or one of many other maladies prevalent in the early seventeenth century. He postponed his planned visit to Antwerp in order to recuperate. Finally, on 2 May 1603, his friend Emmanuel Ximenes wrote: "Praise God that your indisposition has ended ... if the Pisan air is suited to your recovery then do not change it."

In the winter of 1603-4 Neri embarked on what would become a seven-year-long visit to his friend's palace in Antwerp. There, he would learn many new techniques, and ultimately have special glass vessels made and presented to Philip William, Prince of Orange. Upon his return to Tuscany in 1611, he sat down to write the book for which he is most remembered, L'Arte Vetraria. Two years after publication, in 1614, the priest would be dead. According to the only known account, printed over two centuries later by Francesco Inghirami, Neri fell ill and passed within a short time of unknown causes.