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

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

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

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.

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.

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 2003.

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 2003.

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 2003.

Artificial Gems Reprise

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. The following post first appeared on 16 September 2003:

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

Artificial Gems

17th century girandole pendant.

In the fifth part of Neri's 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.

Gold-Ruby Glass

Gold ruby glass, at the Wittelsbacher in the Munich Residenz.
The glass with the lid is attributed to Johannes Kunckel.

What has become the most celebrated glass recipe in Neri's book is also one of the shortest. Chapter 129 is entitled "Transparent Red." In it, he describes his method for making gold-ruby glass. A deep red colored glass made with metallic gold. Because of the difficulty in making it, among later glassmakers, it became something of a holy grail. Here is Neri's recipe for gold-ruby glass in its entirety:

Calcine gold so that it becomes a red powder. This calcination is done repeatedly with aqua regis, pouring it over [the gold] five or six times. Then put this gold powder into a small earthen pan to calcine in the furnace until it becomes a red powder, which will take place after many days. Sprinkle this red powder of gold [gold chloride] over the fused glass. Use fine cristallo, thrown in water many times. This gold powder, given in proportion little by little, will make the transparent ruby red glass; but you must experiment in order to find it. 

To be blunt, by itself this recipe does not give enough information to reliably make the fabled red glass. Neri must have known this, as alluded to in the line "but you must experiment in order to find it." Neri's German translator Johannes Kunckel successfully made gold-ruby glass, but he too declined to disclose his method, although several beautiful examples of his do survive. Much later it became generally known that the addition of small amounts of tin will produce a dependable red color. It was not until the twentieth century that the underlying chemistry was understood. 

It appears that this color glass was produced even earlier by mosaic makers and enamellers, who routinely added tin to opacify the melt. The difference between their creations and transparent ruby glass was the amount of tin used. Deep transparent ruby glass requires only miniscule amounts of tin and gold. More tin makes the glass opaque and lightens the red color. There was one final secret necessary; the glass must be 'struck' in a special process. The freshly made glass object is cooled then reheated to bring out the deep red color. In 1568 Benvenuto Cellini clearly described the striking method for gold-ruby enamel.

 … when it has once more cooled you put it in [the kiln] again, but this time with a much weaker fire, until you see it little by little reddening, but take great heed that when it has got the good color you want, you draw it rapidly from the fire & cool it with the bellows, because too much firing will give it so strong a color as to make it almost black.

 Benvenuto Cellini, The Treatises Of Benvenuto Cellini On Goldsmithing And Sculpture, Charles Robert Ashbee, ed., tr. (New York: Dover, 1967), p. 20.