What Goes Around Comes Around

 

The German city of Ulm in the 16th century

Georg Braun, Franz Hogenberg 1570-78

(Click image to enlarge.)

In the spring and summer of 1525, peasants and farmers throughout German speaking Europe staged a popular revolt now called the Deutscher Bauernkrieg. [1] At the heart of the matter was an oppressive system of taxation run by the Roman Catholic Church, in which little or none of the revenue was used to improve life locally. Often, action was lead by Protestant clergy, but to little effect against the mercenary armies hired by the aristocracy. In the end, up to 100,000 of the poorly armed and organized peasants were slaughtered.

Along the banks of the Danube River in southern Germany lies the ancient city of Ulm. Besides being the birthplace of Albert Einstein, Ulm was, in the sixteenth century, near the center of the Peasant’s Revolt, which brings us to a curious story which traces the migration of a technical recipe from Ulm over the alps to Venice, then to Sienna and finally Florence. The recipe is for the metal alloy to make mirrors, and it is told from one friend to another while chatting amiably in Venice.

Among other things, he said that he had made one [concave mirror] almost half a braccio across [about 13 inches], which extended the clear rays of its brightness more than a quarter of a German league when he caught the sun with it. One day, when for amusement he was standing in a window to watch a review of armed men in the city of Ulm, he bore with the sphere of his mirror for a quarter of an hour on the back of the shoulder armor of one of those soldiers. This not only caused so much heat that it became almost unbearable to the soldier, but it inflamed so that it kindled his jacket  underneath and burned it for him, cooking his flesh to his very great torment. Since he did not understand who caused this, he said that God had miraculously sent that fire on him for his great sins. [2]

The story was told to Vannoccio Biringuccio, who recalls it in 1540 in his Pirotechnia, the first printed book devoted to metallurgy. Specifically, the recipe is a variant of what today we would call white bronze, which as Biringuccio states is similar to the metal used to cast bells. He recites ancient formulations that used three parts copper and one part tin. To this was added 1/18th part of antimony and optionally 1/24th part of fine silver to give it a neutral color. Indeed, other ancient formulations for what was known as speculum metal specify a 3:1 ratio of copper to tin. He continues,

But nowadays most of the masters who make them take three parts of tin and one of copper, and melt these together. When they are melted, for every pound of this material, they throw in one ounce of tartar and half an ounce of powdered arsenic, and let them fume and melt and incorporate well. 

Biringuccio’s version reverses the copper and tin ratio from the classical composition. Compare it with Antonio Neri’s prescription which appears half a century later, it is almost identical:

Have 3 lbs of well-purified tin, and 1 lb of copper also purified. Melt these two metals, first the copper, then the tin. When they fuse thoroughly, throw onto them 6 oz of just singed red wine tartar, and 1½ oz of saltpeter, then ¼ oz of alum, and 2 oz of arsenic. Leave these all to vaporize, and then cast [the metal] into the form of a sphere. You will have good material, which when you burnish and polish, will look most fine. This mixture is called acciaio and is used to make spherical mirrors.

To be clear, the tartar, saltpeter and alum act as a surface flux - they form a layer that floats on the liquid metal, preventing oxides from forming, which can foul the melt.  their addition does not change the base alloy composition.

The similarity of the two recipes alone is not enough to draw any conclusions. Biringuccio himself reports that the contemporary artisans favored the tin rich formulation. However, there are other details to consider. The Sienese born Biringuccio was something of a hero in Florence where Antonio Neri was raised. The famous metallurgist helped cast cannons, mortars and guns for the Florentines to defend themselves in the late 1520s, when the city was under siege, just a few years after Biringuccio’s conversation in Venice with his German friend from Ulm.

Neri was definitely familiar with Biringuccio’s book Pirotechnia. In fact, the introduction to Neri’s own book L’Arte Vetraria is patterned after the metallurgist’s survey of glassmaking.  In his chapter 14, book 2 Biringuccio wrote:

… it [glass] is one of the effects and real fruits of the art of fire, because every product found in the interior of the earth is either stone, metal, or one of the semi-minerals.  Glass is seen to resemble all of them, although in all respects it depends on art. [3]

And here is the opening to Neri’s introduction a half century later in 1612,

Without a doubt, glass is a true fruit of the art of fire, as it can so closely resemble all kinds of rocks and minerals, yet it is a compound, and made by art. [4]

Both passages go on to cover much of the same ground, albeit with a change in focus reflective of new thinking about chemistry and nature. In one sense, Neri is paying homage to his distinguished predecessor, and there can be little doubt that he read Biringuccio’s book and its technical recipes closely. 

Lastly, the story of the burning mirror itself mimics a widely known story about the Greek polymath Archimedes. About 200 BCE during the siege of Syracuse, he is said to have set invading Roman ships on fire with a concave mirror, which focused the radiation of the sun.

In fact a depiction of this scene was painted in Florence on the walls of the Uffizi Palace in 1600, when Neri was at the height of his employment for the ruling Medici family. This particular rendering would have been all but impossible for him to miss. 

Uffizi Gallery, Florence, Italy, Wall painting
showing the Greek mathematician Archimedes' mirror 
being used to burn Roman military ships. 
Painted in 1600 by Giulio Parigi.

In the years leading to the publication of Neri’s book, he left his home in Florence and traveled to visit a friend in Antwerp. If he had read the book on metallurgy early, perhaps as part of his education, then he was already familiar with the mirror alloy recipe. If he followed the route suggested by his friend, he would have taken the recipe back to Venice, and then over the Alps and likely through Ulm on his way north to the Low Countries, where he would spend the next seven years before returning to Italy. [5]

[1] For more on the German peasant wars of 1524-25 see https://en.wikipedia.org/wiki/German_Peasants%27_War
[2] Vannoccio Biringuccio, Pirotechnia. Ed., Tr. Cyril Stanley Smith, Martha Teach Gnudi (New York: Basic Books, 1959), pp. 385-390. (Original Italian published in 1540.)
[3] Antonio Neri, L’Arte Vetraria (Florence: Giunti, 1612). p. iv.
[4] Ibid,  p.126 (in original, ff.41r-44v).

[5] Special thanks to Jamie Hall (@PrimitiveMethod) for inspiring this post.

What Goes Around Comes Around

The German city of Ulm in the 16th century

Georg Braun, Franz Hogenberg 1570-78

(Click image to enlarge.)

In the spring and summer of 1525, peasants and farmers throughout German speaking Europe staged a popular revolt now called the Deutscher Bauernkrieg. [1] At the heart of the matter was an oppressive system of taxation run by the Roman Catholic Church, in which little or none of the revenue was used to improve life locally. Often, action was lead by Protestant clergy, but to little effect against the mercenary armies hired by the aristocracy. In the end, up to 100,000 of the poorly armed and organized peasants were slaughtered.

Along the banks of the Danube River in southern Germany lies the ancient city of Ulm. Besides being the birthplace of Albert Einstein, Ulm was, in the sixteenth century, near the center of the Peasant’s Revolt, which brings us to a curious story which traces the migration of a technical recipe from Ulm over the alps to Venice, then to Sienna and finally Florence. The recipe is for the metal alloy to make mirrors, and it is told from one friend to another while chatting amiably in Venice.

Among other things, he said that he had made one [concave mirror] almost half a braccio across [about 13 inches], which extended the clear rays of its brightness more than a quarter of a German league when he caught the sun with it. One day, when for amusement he was standing in a window to watch a review of armed men in the city of Ulm, he bore with the sphere of his mirror for a quarter of an hour on the back of the shoulder armor of one of those soldiers. This not only caused so much heat that it became almost unbearable to the soldier, but it inflamed so that it kindled his jacket  underneath and burned it for him, cooking his flesh to his very great torment. Since he did not understand who caused this, he said that God had miraculously sent that fire on him for his great sins. [2]

The story was told to Vannoccio Biringuccio, who recalls it in 1540 in his Pirotechnia, the first printed book devoted to metallurgy. Specifically, the recipe is a variant of what today we would call white bronze, which as Biringuccio states is similar to the metal used to cast bells. He recites ancient formulations that used three parts copper and one part tin. To this was added 1/18th part of antimony and optionally 1/24th part of fine silver to give it a neutral color. Indeed, other ancient formulations for what was known as speculum metal specify a 3:1 ratio of copper to tin. He continues,

But nowadays most of the masters who make them take three parts of tin and one of copper, and melt these together. When they are melted, for every pound of this material, they throw in one ounce of tartar and half an ounce of powdered arsenic, and let them fume and melt and incorporate well. 

Biringuccio’s version reverses the copper and tin ratio from the classical composition. Compare it with Antonio Neri’s prescription which appears half a century later, it is almost identical:

Have 3 lbs of well-purified tin, and 1 lb of copper also purified. Melt these two metals, first the copper, then the tin. When they fuse thoroughly, throw onto them 6 oz of just singed red wine tartar, and 1½ oz of saltpeter, then ¼ oz of alum, and 2 oz of arsenic. Leave these all to vaporize, and then cast [the metal] into the form of a sphere. You will have good material, which when you burnish and polish, will look most fine. This mixture is called acciaio and is used to make spherical mirrors.

To be clear, the tartar, saltpeter and alum act as a surface flux - they form a layer that floats on the liquid metal, preventing oxides from forming, which can foul the melt.  their addition does not change the base alloy composition.

The similarity of the two recipes alone is not enough to draw any conclusions. Biringuccio himself reports that the contemporary artisans favored the tin rich formulation. However, there are other details to consider. The Sienese born Biringuccio was something of a hero in Florence where Antonio Neri was raised. The famous metallurgist helped cast cannons, mortars and guns for the Florentines to defend themselves in the late 1520s, when the city was under siege, just a few years after Biringuccio’s conversation in Venice with his German friend from Ulm.

Neri was definitely familiar with Biringuccio’s book Pirotechnia. In fact, the introduction to Neri’s own book L’Arte Vetraria is patterned after the metallurgist’s survey of glassmaking.  In his chapter 14, book 2 Biringuccio wrote:

… it [glass] is one of the effects and real fruits of the art of fire, because every product found in the interior of the earth is either stone, metal, or one of the semi-minerals.  Glass is seen to resemble all of them, although in all respects it depends on art. [3]

And here is the opening to Neri’s introduction a half century later in 1612,

Without a doubt, glass is a true fruit of the art of fire, as it can so closely resemble all kinds of rocks and minerals, yet it is a compound, and made by art. [4]

Both passages go on to cover much of the same ground, albeit with a change in focus reflective of new thinking about chemistry and nature. In one sense, Neri is paying homage to his distinguished predecessor, and there can be little doubt that he read Biringuccio’s book and its technical recipes closely. 

Lastly, the story of the burning mirror itself mimics a widely known story about the Greek polymath Archimedes. About 200 BCE during the siege of Syracuse, he is said to have set invading Roman ships on fire with a concave mirror, which focused the radiation of the sun.

In fact a depiction of this scene was painted in Florence on the walls of the Uffizi Palace in 1600, when Neri was at the height of his employment for the ruling Medici family. This particular rendering would have been all but impossible for him to miss. 

Uffizi Gallery, Florence, Italy, Wall painting
showing the Greek mathematician Archimedes' mirror 
being used to burn Roman military ships. 
Painted in 1600 by Giulio Parigi.

In the years leading to the publication of Neri’s book, he left his home in Florence and traveled to visit a friend in Antwerp. If he had read the book on metallurgy early, perhaps as part of his education, then he was already familiar with the mirror alloy recipe. If he followed the route suggested by his friend, he would have taken the recipe back to Venice, and then over the Alps and likely through Ulm on his way north to the Low Countries, where he would spend the next seven years before returning to Italy. [5]

[1] For more on the German peasant wars of 1524-25 see https://en.wikipedia.org/wiki/German_Peasants%27_War
[2] Vannoccio Biringuccio, Pirotechnia. Ed., Tr. Cyril Stanley Smith, Martha Teach Gnudi (New York: Basic Books, 1959), pp. 385-390. (Original Italian published in 1540.)
[3] Antonio Neri, L’Arte Vetraria (Florence: Giunti, 1612). p. iv.
[4] Ibid,  p.126 (in original, ff.41r-44v).

[5] Special thanks to Jamie Hall (@PrimitiveMethod) for inspiring this post.

What Goes Around Comes Around

The German city of Ulm in the 16th century

Georg Braun, Franz Hogenberg 1570-78

(Click image to enlarge.)

In the spring and summer of 1525, peasants and farmers throughout German speaking Europe staged a popular revolt now called the Deutscher Bauernkrieg. [1] At the heart of the matter was an oppressive system of taxation run by the Roman Catholic Church, in which little or none of the revenue was used to improve life locally. Often, action was lead by Protestant clergy, but to little effect against the mercenary armies hired by the aristocracy. In the end, up to 100,000 of the poorly armed and organized peasants were slaughtered.

Along the banks of the Danube River in southern Germany lies the ancient city of Ulm. Besides being the birthplace of Albert Einstein, Ulm was, in the sixteenth century, near the center of the Peasant’s Revolt, which brings us to a curious story which traces the migration of a technical recipe from Ulm over the alps to Venice, then to Sienna and finally Florence. The recipe is for the metal alloy to make mirrors, and it is told from one friend to another while chatting amiably in Venice.

Among other things, he said that he had made one [concave mirror] almost half a braccio across [about 13 inches], which extended the clear rays of its brightness more than a quarter of a German league when he caught the sun with it. One day, when for amusement he was standing in a window to watch a review of armed men in the city of Ulm, he bore with the sphere of his mirror for a quarter of an hour on the back of the shoulder armor of one of those soldiers. This not only caused so much heat that it became almost unbearable to the soldier, but it inflamed so that it kindled his jacket  underneath and burned it for him, cooking his flesh to his very great torment. Since he did not understand who caused this, he said that God had miraculously sent that fire on him for his great sins. [2]

The story was told to Vannoccio Biringuccio, who recalls it in 1540 in his Pirotechnia, the first printed book devoted to metallurgy. Specifically, the recipe is a variant of what today we would call white bronze, which as Biringuccio states is similar to the metal used to cast bells. He recites ancient formulations that used three parts copper and one part tin. To this was added 1/18th part of antimony and optionally 1/24th part of fine silver to give it a neutral color. Indeed, other ancient formulations for what was known as speculum metal specify a 3:1 ratio of copper to tin. He continues,

But nowadays most of the masters who make them take three parts of tin and one of copper, and melt these together. When they are melted, for every pound of this material, they throw in one ounce of tartar and half an ounce of powdered arsenic, and let them fume and melt and incorporate well. 

Biringuccio’s version reverses the copper and tin ratio from the classical composition. Compare it with Antonio Neri’s prescription which appears half a century later, it is almost identical:

Have 3 lbs of well-purified tin, and 1 lb of copper also purified. Melt these two metals, first the copper, then the tin. When they fuse thoroughly, throw onto them 6 oz of just singed red wine tartar, and 1½ oz of saltpeter, then ¼ oz of alum, and 2 oz of arsenic. Leave these all to vaporize, and then cast [the metal] into the form of a sphere. You will have good material, which when you burnish and polish, will look most fine. This mixture is called acciaio and is used to make spherical mirrors.

To be clear, the tartar, saltpeter and alum act as a surface flux - they form a layer that floats on the liquid metal, preventing oxides from forming, which can foul the melt.  their addition does not change the base alloy composition.

The similarity of the two recipes alone is not enough to draw any conclusions. Biringuccio himself reports that the contemporary artisans favored the tin rich formulation. However, there are other details to consider. The Sienese born Biringuccio was something of a hero in Florence where Antonio Neri was raised. The famous metallurgist helped cast cannons, mortars and guns for the Florentines to defend themselves in the late 1520s, when the city was under siege, just a few years after Biringuccio’s conversation in Venice with his German friend from Ulm.

Neri was definitely familiar with Biringuccio’s book Pirotechnia. In fact, the introduction to Neri’s own book L’Arte Vetraria is patterned after the metallurgist’s survey of glassmaking.  In his chapter 14, book 2 Biringuccio wrote:

… it [glass] is one of the effects and real fruits of the art of fire, because every product found in the interior of the earth is either stone, metal, or one of the semi-minerals.  Glass is seen to resemble all of them, although in all respects it depends on art. [3]

And here is the opening to Neri’s introduction a half century later in 1612,

Without a doubt, glass is a true fruit of the art of fire, as it can so closely resemble all kinds of rocks and minerals, yet it is a compound, and made by art. [4]

Both passages go on to cover much of the same ground, albeit with a change in focus reflective of new thinking about chemistry and nature. In one sense, Neri is paying homage to his distinguished predecessor, and there can be little doubt that he read Biringuccio’s book and its technical recipes closely. 

Lastly, the story of the burning mirror itself mimics a widely known story about the Greek polymath Archimedes. About 200 BCE during the siege of Syracuse, he is said to have set invading Roman ships on fire with a concave mirror, which focused the radiation of the sun.

In fact a depiction of this scene was painted in Florence on the walls of the Uffizi Palace in 1600, when Neri was at the height of his employment for the ruling Medici family. This particular rendering would have been all but impossible for him to miss. 

Uffizi Gallery, Florence, Italy, Wall painting
showing the Greek mathematician Archimedes' mirror 
being used to burn Roman military ships. 
Painted in 1600 by Giulio Parigi.

In the years leading to the publication of Neri’s book, he left his home in Florence and traveled to visit a friend in Antwerp. If he had read the book on metallurgy early, perhaps as part of his education, then he was already familiar with the mirror alloy recipe. If he followed the route suggested by his friend, he would have taken the recipe back to Venice, and then over the Alps and likely through Ulm on his way north to the Low Countries, where he would spend the next seven years before returning to Italy. [5]

[1] For more on the German peasant wars of 1524-25 see https://en.wikipedia.org/wiki/German_Peasants%27_War
[2] Vannoccio Biringuccio, Pirotechnia. Ed., Tr. Cyril Stanley Smith, Martha Teach Gnudi (New York: Basic Books, 1959), pp. 385-390. (Original Italian published in 1540.)
[3] Antonio Neri, L’Arte Vetraria (Florence: Giunti, 1612). p. iv.
[4] Ibid,  p.126 (in original, ff.41r-44v).

[5] Special thanks to Jamie Hall (@PrimitiveMethod) for inspiring this post.

What Goes Around Comes Around

The German city of Ulm in the 16th century

Georg Braun, Franz Hogenberg 1570-78

(Click image to enlarge.)

In the spring and summer of 1525, peasants and farmers throughout German speaking Europe staged a popular revolt now called the Deutscher Bauernkrieg. [1] At the heart of the matter was an oppressive system of taxation run by the Roman Catholic Church, in which little or none of the revenue was used to improve life locally. Often, action was lead by Protestant clergy, but to little effect against the mercenary armies hired by the aristocracy. In the end, up to 100,000 of the poorly armed and organized peasants were slaughtered.

Along the banks of the Danube River in southern Germany lies the ancient city of Ulm. Besides being the birthplace of Albert Einstein, Ulm was, in the sixteenth century, near the center of the Peasant’s Revolt, which brings us to a curious story which traces the migration of a technical recipe from Ulm over the alps to Venice, then to Sienna and finally Florence. The recipe is for the metal alloy to make mirrors, and it is told from one friend to another while chatting amiably in Venice.

Among other things, he said that he had made one [concave mirror] almost half a braccio across [about 13 inches], which extended the clear rays of its brightness more than a quarter of a German league when he caught the sun with it. One day, when for amusement he was standing in a window to watch a review of armed men in the city of Ulm, he bore with the sphere of his mirror for a quarter of an hour on the back of the shoulder armor of one of those soldiers. This not only caused so much heat that it became almost unbearable to the soldier, but it inflamed so that it kindled his jacket  underneath and burned it for him, cooking his flesh to his very great torment. Since he did not understand who caused this, he said that God had miraculously sent that fire on him for his great sins. [2]

The story was told to Vannoccio Biringuccio, who recalls it in 1540 in his Pirotechnia, the first printed book devoted to metallurgy. Specifically, the recipe is a variant of what today we would call white bronze, which as Biringuccio states is similar to the metal used to cast bells. He recites ancient formulations that used three parts copper and one part tin. To this was added 1/18th part of antimony and optionally 1/24th part of fine silver to give it a neutral color. Indeed, other ancient formulations for what was known as speculum metal specify a 3:1 ratio of copper to tin. He continues,

But nowadays most of the masters who make them take three parts of tin and one of copper, and melt these together. When they are melted, for every pound of this material, they throw in one ounce of tartar and half an ounce of powdered arsenic, and let them fume and melt and incorporate well. 

Biringuccio’s version reverses the copper and tin ratio from the classical composition. Compare it with Antonio Neri’s prescription which appears half a century later, it is almost identical:

Have 3 lbs of well-purified tin, and 1 lb of copper also purified. Melt these two metals, first the copper, then the tin. When they fuse thoroughly, throw onto them 6 oz of just singed red wine tartar, and 1½ oz of saltpeter, then ¼ oz of alum, and 2 oz of arsenic. Leave these all to vaporize, and then cast [the metal] into the form of a sphere. You will have good material, which when you burnish and polish, will look most fine. This mixture is called acciaio and is used to make spherical mirrors.

To be clear, the tartar, saltpeter and alum act as a surface flux - they form a layer that floats on the liquid metal, preventing oxides from forming, which can foul the melt.  their addition does not change the base alloy composition.

The similarity of the two recipes alone is not enough to draw any conclusions. Biringuccio himself reports that the contemporary artisans favored the tin rich formulation. However, there are other details to consider. The Sienese born Biringuccio was something of a hero in Florence where Antonio Neri was raised. The famous metallurgist helped cast cannons, mortars and guns for the Florentines to defend themselves in the late 1520s, when the city was under siege, just a few years after Biringuccio’s conversation in Venice with his German Friend from Ulm.

Neri was definitely familiar with Biringuccio’s book Pirotechnia. In fact, the introduction to Neri’s own book L’Arte Vetraria is patterned after the metallurgist’s survey of glassmaking.  In his chapter 14, book 2 Biringuccio wrote:

… it [glass] is one of the effects and real fruits of the art of fire, because every product found in the interior of the earth is either stone, metal, or one of the semi-minerals.  Glass is seen to resemble all of them, although in all respects it depends on art. [3]

And here is the opening to Neri’s introduction a half century later in 1612,

Without a doubt, glass is a true fruit of the art of fire, as it can so closely resemble all kinds of rocks and minerals, yet it is a compound, and made by art. [4]

Both passages go on to cover much of the same ground, albeit with a change in focus reflective of new thinking about chemistry and nature. In one sense, Neri is paying homage to his distinguished predecessor, and there can be little doubt that he read Biringuccio’s book and its technical recipes closely. 

Lastly, the story of the burning mirror itself mimics a widely known story about the Greek polymath Archimedes. About 200 BCE during the siege of Syracuse, he is said to have set invading Roman ships on fire with a concave mirror, which focused the radiation of the sun.

In fact a depiction of this scene was painted in Florence on the walls of the Uffizi Palace in 1600, when Neri was at the height of his employment for the ruling Medici family. This particular rendering would have been all but impossible for him to miss. 

Uffizi Gallery, Florence, Italy, Wall painting
showing the Greek mathematician Archimedes' mirror 
being used to burn Roman military ships. 
Painted in 1600 by Giulio Parigi.

In the years leading to the publication of Neri’s book, he left his home in Florence and traveled to visit a friend in Antwerp. If he had read the book on metallurgy early, perhaps as part of his education, then he was already familiar with the mirror alloy recipe. If he followed the route suggested by his friend, he would have taken the recipe back to Venice, and then over the Alps and likely through Ulm on his way north to the Low Countries, where he would spend the next seven years before returning to Italy. [5]

[1] For more on the German peasant wars of 1524-25 see https://en.wikipedia.org/wiki/German_Peasants%27_War
[2] Vannoccio Biringuccio, Pirotechnia. Ed., Tr. Cyril Stanley Smith, Martha Teach Gnudi (New York: Basic Books, 1959), pp. 385-390. (Original Italian published in 1540.)
[3] Antonio Neri, L’Arte Vetraria (Florence: Giunti, 1612). p. iv.
[4] Ibid,  p.126 (in original, ff.41r-44v).

[5] Special thanks to Jamie Hall (@PrimitiveMethod) for inspiring this post.

What Goes Around Comes Around

The German city of Ulm in the 16th century

Georg Braun, Franz Hogenberg 1570-78

(Click image to enlarge.)

In the spring and summer of 1525, peasants and farmers throughout German speaking Europe staged a popular revolt now called the Deutscher Bauernkrieg. [1] At the heart of the matter was an oppressive system of taxation run by the Roman Catholic Church, in which little or none of the revenue was used to improve life locally. Often, action was lead by Protestant clergy, but to little effect against the mercenary armies hired by the aristocracy. In the end, up to 100,000 of the poorly armed and organized peasants were slaughtered.

Along the banks of the Danube River in southern Germany lies the ancient city of Ulm. Besides being the birthplace of Albert Einstein, Ulm was, in the sixteenth century, near the center of the Peasant’s Revolt, which brings us to a curious story which traces the migration of a technical recipe from Ulm over the alps to Venice, then to Sienna and finally Florence. The recipe is for the metal alloy to make mirrors, and it is told from one friend to another while chatting amiably in Venice.

Among other things, he said that he had made one [concave mirror] almost half a braccio across [about 13 inches], which extended the clear rays of its brightness more than a quarter of a German league when he caught the sun with it. One day, when for amusement he was standing in a window to watch a review of armed men in the city of Ulm, he bore with the sphere of his mirror for a quarter of an hour on the back of the shoulder armor of one of those soldiers. This not only caused so much heat that it became almost unbearable to the soldier, but it inflamed so that it kindled his jacket  underneath and burned it for him, cooking his flesh to his very great torment. Since he did not understand who caused this, he said that God had miraculously sent that fire on him for his great sins. [2]

The story was told to Vannoccio Biringuccio, who recalls it in 1540 in his Pirotechnia, the first printed book devoted to metallurgy. Specifically, the recipe is a variant of what today we would call white bronze, which as Biringuccio states is similar to the metal used to cast bells. He recites ancient formulations that used three parts copper and one part tin. To this was added 1/18th part of antimony and optionally 1/24th part of fine silver to give it a neutral color. Indeed, other ancient formulations for what was known as speculum metal specify a 3:1 ratio of copper to tin. He continues,

But nowadays most of the masters who make them take three parts of tin and one of copper, and melt these together. When they are melted, for every pound of this material, they throw in one ounce of tartar and half an ounce of powdered arsenic, and let them fume and melt and incorporate well. 

Biringuccio’s version reverses the copper and tin ratio from the classical composition. Compare it with Antonio Neri’s prescription which appears half a century later, it is almost identical:

Have 3 lbs of well-purified tin, and 1 lb of copper also purified. Melt these two metals, first the copper, then the tin. When they fuse thoroughly, throw onto them 6 oz of just singed red wine tartar, and 1½ oz of saltpeter, then ¼ oz of alum, and 2 oz of arsenic. Leave these all to vaporize, and then cast [the metal] into the form of a sphere. You will have good material, which when you burnish and polish, will look most fine. This mixture is called acciaio and is used to make spherical mirrors.

To be clear, the tartar, saltpeter and alum act as a surface flux - they form a layer that floats on the liquid metal, preventing oxides from forming, which can foul the melt.  their addition does not change the base alloy composition.

The similarity of the two recipes alone is not enough to draw any conclusions. Biringuccio himself reports that the contemporary artisans favored the tin rich formulation. However, there are other details to consider. The Sienese born Biringuccio was something of a hero in Florence where Antonio Neri was raised. The famous metallurgist helped cast cannons, mortars and guns for the Florentines to defend themselves in the late 1520s, when the city was under siege, just a few years after Biringuccio’s conversation in Venice with his German Friend from Ulm.

Neri was definitely familiar with Biringuccio’s book Pirotechnia. In fact, the introduction to Neri’s own book L’Arte Vetraria is patterned after the metallurgist’s survey of glassmaking.  In his chapter 14, book 2 Biringuccio wrote:

… it [glass] is one of the effects and real fruits of the art of fire, because every product found in the interior of the earth is either stone, metal, or one of the semi-minerals.  Glass is seen to resemble all of them, although in all respects it depends on art. [3]

And here is the opening to Neri’s introduction a half century later in 1612,

Without a doubt, glass is a true fruit of the art of fire, as it can so closely resemble all kinds of rocks and minerals, yet it is a compound, and made by art. [4]

Both passages go on to cover much of the same ground, albeit with a change in focus reflective of new thinking about chemistry and nature. In one sense, Neri is paying homage to his distinguished predecessor, and there can be little doubt that he read Biringuccio’s book and its technical recipes closely. 

Lastly, the story of the burning mirror itself mimics a widely known story about the Greek polymath Archimedes. About 200 BCE during the siege of Syracuse, he is said to have set invading Roman ships on fire with a concave mirror, which focused the radiation of the sun.

In fact a depiction of this scene was painted in Florence on the walls of the Uffizi Palace in 1600, when Neri was at the height of his employment for the ruling Medici family. This particular rendering would have been all but impossible for him to miss. 

Uffizi Gallery, Florence, Italy, Wall painting
showing the Greek mathematician Archimedes' mirror 
being used to burn Roman military ships. 
Painted in 1600 by Giulio Parigi.

In the years leading to the publication of Neri’s book, he left his home in Florence and traveled to visit a friend in Antwerp. If he had read the book on metallurgy early, perhaps as part of his education, then he was already familiar with the mirror alloy recipe. If he followed the route suggested by his friend, he would have taken the recipe back to Venice, and then over the Alps and likely through Ulm on his way north to the Low Countries, where he would spend the next seven years before returning to Italy. [5]

[1] For more on the German peasant wars of 1524-25 see https://en.wikipedia.org/wiki/German_Peasants%27_War
[2] Vannoccio Biringuccio, Pirotechnia. Ed., Tr. Cyril Stanley Smith, Martha Teach Gnudi (New York: Basic Books, 1959), pp. 385-390. (Original Italian published in 1540.)
[4] Ibid,  p.126 (in original, ff.41r-44v).
[3] Antonio Neri, L’Arte Vetraria (Florence: Giunti, 1612). p. iv.

[5] Special thanks to Jamie Hall (@PrimitiveMethod) for inspiring this post.

Creative Use of Mirrors

The German city of Ulm in the 16th century

Georg Braun, Franz Hogenberg 1570-78

(Click either image to enlarge.)

Along the banks of the Danube River in southern Germany lies the ancient city of Ulm. Besides being the birthplace of Albert Einstein, at the start of the Protestant Reformation in the sixteenth century, Ulm was near the epicenter of the bloody Peasant’s Revolt. 

In the spring and summer of 1525, peasants and farmers throughout German speaking Europe staged a popular revolt now called the Deutscher Bauernkrieg. [1] At the heart of the matter was an oppressive system of taxation run by the Catholic Church, in which little or none of the revenue was used to improve life locally. Often, action was lead by Protestant clergy, but to little effect against the mercenary armies hired by the aristocracy. It was a very brutal affair; in the end, up to 100,000 of the poorly armed and organized peasants were slaughtered.

This brings us to a curious story of retribution oddly reminiscent of the ancient legend of Archimedes' burning mirror.  Through this account, we can trace the migration of a technical recipe from Ulm over the alps to Venice, then to Sienna and finally to Florence. The recipe is for the metal alloy to make mirrors, and it is told from one friend to another while chatting amiably in Venice, years after the revolt.

Among other things, he said that he had made one [concave mirror] almost half a braccio across [about 13 inches], which extended the clear rays of its brightness more than a quarter of a German league when he caught the sun with it. One day, when for amusement he was standing in a window to watch a review of armed men in the city of Ulm, he bore with the sphere of his mirror for a quarter of an hour on the back of the shoulder armor of one of those soldiers. This not only caused so much heat that it became almost unbearable to the soldier, but it inflamed so that it kindled his jacket  underneath and burned it for him, cooking his flesh to his very great torment. Since he did not understand who caused this, he said that God had miraculously sent that fire on him for his great sins. [2]

The story was told to Vannoccio Biringuccio, who recalls it in 1540 in his Pirotechnia, the first printed book devoted to metallurgy. Specifically, the recipe is a variant of what today we would call white bronze, which as Biringuccio states is similar to the metal used to cast bells. He recites ancient formulations that used three parts copper and one part tin. To this was added 1/18th part of antimony and optionally 1/24th part of fine silver to give it a neutral color. Indeed, other ancient formulations for what was known as speculum metal specify a 3:1 ratio of copper to tin. He continues,

But nowadays most of the masters who make them take three parts of tin and one of copper, and melt these together. When they are melted, for every pound of this material, they throw in one ounce of tartar and half an ounce of powdered arsenic, and let them fume and melt and incorporate well. 

Biringuccio’s version reverses the copper and tin ratio from the classical composition. Compare it with Antonio Neri’s prescription which appears half a century later, it is almost identical:

Have 3 lbs of well-purified tin, and 1 lb of copper also purified. Melt these two metals, first the copper, then the tin. When they fuse thoroughly, throw onto them 6 oz of just singed red wine tartar, and 1½ oz of saltpeter, then ¼ oz of alum, and 2 oz of arsenic. Leave these all to vaporize, and then cast [the metal] into the form of a sphere. You will have good material, which when you burnish and polish, will look most fine. This mixture is called acciaio and is used to make spherical mirrors.

To be clear, the tartar, saltpeter and alum act as a surface flux - they form a layer that floats on the liquid metal, preventing oxides from forming, which can foul the melt.  their addition does not change the base alloy composition.

The similarity of the two recipes alone is not enough to draw any conclusions. Biringuccio himself reports that the contemporary artisans favored the tin rich formulation. However, there are other details to consider. The Sienese born Biringuccio was something of a hero in Florence where alchemist Antonio Neri was raised. The famous metallurgist helped cast cannons, mortars and guns for the Florentines to defend themselves in the late 1520s, when the city was under siege, just a few years after Biringuccio’s conversation in Venice with his German Friend from Ulm.

Neri was definitely familiar with Biringuccio’s book Pirotechnia. In fact, the introduction to Neri’s own book on glassmaking,  L’Arte Vetraria, is patterned after the metallurgist’s survey of glassmaking.  In his chapter 14, book 2 Biringuccio wrote:

… it [glass] is one of the effects and real fruits of the art of fire, because every product found in the interior of the earth is either stone, metal, or one of the semi-minerals.  Glass is seen to resemble all of them, although in all respects it depends on art. [3]

And here is the opening to Neri’s introduction a half century later in 1612,

Without a doubt, glass is a true fruit of the art of fire, as it can so closely resemble all kinds of rocks and minerals, yet it is a compound, and made by art. [4]

Both passages go on to cover much of the same ground, albeit with a change in focus reflective of new thinking about chemistry and nature. In one sense, Neri is paying homage to his distinguished predecessor, and there can be little doubt that he read Biringuccio’s book and its technical recipes closely. 

In the years leading to the publication of Neri’s book, he left his home in Florence and traveled to visit a friend in Antwerp. If he had read the book on metallurgy early, perhaps as part of his education, then he was already familiar with the mirror alloy recipe. If he followed the route suggested by his friend, he would have taken the recipe back to Venice, and then over the Alps and likely through Ulm on his way north to the Low Countries, where he would spend the next seven years before returning to Italy. [5]

* This post first appeared in a slightly different form on 25 January 2016.
[1] For more on the German peasant wars of 1524-25 see https://en.wikipedia.org/wiki/German_Peasants%27_War
[2] Vannoccio Biringuccio, Pirotechnia. Ed., Tr. Cyril Stanley Smith, Martha Teach Gnudi (New York: Basic Books, 1959), pp. 385-390. (Original Italian published in 1540.)
[4] Ibid,  p.126 (in original, ff.41r-44v).
[3] Antonio Neri, L’Arte Vetraria (Florence: Giunti, 1612). p. iv.

[5] Special thanks to Jamie Hall (@PrimitiveMethod) for inspiring this post.

A Fast Calendar

A Seasons clock showing an astronomical year.

Courtesy  of  worth1000.com

Yesterday was the fourth of October. Imagine waking up this morning to discover that it is not the fifth but the fifteenth of the month; ten days have gone missing. This is exactly what happened in 1582. In accordance with a proclamation by Pope Gregory XIII, the calendar was jumped forward. The day after Thursday, 4 October, was Friday, 15 October. For the Roman Catholic world, the intervening ten days were removed from the calendar and never took place.

The seasons cycle from spring to summer to autumn to winter and back again as the earth traces its orbit around the sun. Think of this annual cycle as the dial of a giant clock representing the actual length of a year. Divide the face into quadrants, one for each season. When the earth returns to exactly the same place in its orbit around the sun, exactly one year has passed.We can imagine a giant hand pivoting at the sun, pointing out at the earth as it moves around the clock face. The Julian calendar was devised in the Roman Empire and it served admirably for many centuries. But, by the 16th century, it was seriously out of whack. This system set the length of a year at 365¼ days on average, using the fourth year leap year we are familiar with today. This length of time just slightly over-runs the actual orbit of the earth, which is to say that at the end of 365¼ days, the hand of our cosmic clock was a few minutes past its position from when the year started. In this way, each year the calendar began slightly later than the previous year. This discrepancy was ignored, and the over-run eventually accumulated from minutes to hours to days.

Like a clock that ran fast, after many hundreds of years, the calendar had advanced by about ten days.[1] The date system was in need of a major adjustment; the thing that ultimately forced this calendrical reckoning was Easter. The date of Easter is calculated using the beginning of spring. Because the calendar was running fast, the big day fell a little earlier each year. By the sixteenth century, Easter was falling in early March, which was not acceptable to the Church. Various gradual measures were considered to remedy the situation, but in the end, Pope Gregory XIII (along with a handful of mathematicians) decided to make up for the discrepancy all at once; the ten extra days that had accumulated over the millennium were deleted from the calendar; in effect setting the clock back. In addition, new rules were added for 'leap centuries'. This effectively fixed the problem by slowing the clock ever so slightly, so that on average the hand on the clock cycled extraordinarily close to an astronomical year.[2] And so the Gregorian calendar was born.

Other parts of Europe eventually adopted the changes, some sooner than others. In France, 9 December 1582 was followed by 20 December. A letter sent from Italy on November first of that year might well appear at its destination in France the last week of October, seeming to arrive before it was sent. In the Netherlands and Germany some provinces made the changes while others held out until 1700. Protestant countries did not generally adopt the new system until much later. Britain and her American colonies did not make the change until 1752 by which time the calendars were out of synchronization by a full eleven days.

When the Calendar was adjusted in Italy, glassmaker Antonio Neri was six and a half years old; hardly old enough to remember the event. However, by an odd coincidence he was born on a leap year day, 29 February 1576. In any event, he must have experienced some of the stranger side effects in his adult life, especially when traveling. In making the journey to visit his friend Emmanuel Ximenes, in Antwerp in 1604, if our priest stuck to the route suggested by his friend, he would have remained in Catholic territory until the very end of his journey. Once in the Low Countries, the date of the month would depend on the city. In Protestant controlled regions, like Utrecht, the date would suddenly jump backwards by ten days from nearby Catholic regions, although the days of the week would be consistent. Those crossing the English channel, from Calais France to Dover, for example, would experience a similar effect; it might be early May on one side and late April on the other. In such a crossing, one would experience the disconcerting 'Déjà vu' of living the same date range twice, once as Monday through Friday and then again as the following Thursday through Monday.

If there is a lesson here for close observers of nature, it is that daily living in the early seventeenth century emphasized the difference between the natural world and the contrivances of man. Subtle as it may seem to us today, April does not so much signify the rebirth of our gardens, as the rebirth of our gardens is what we have come to call April. The realignment of the calendar in 1582 emphasized this distinction, foreshadowing philosopher-scientist Alfred Korzybski's premise that "the map is not the territory."

[1] The Catholic Julian Calendar dates from the council of Nicaea in 325 CE.

[2] The authoritative reference on the full extent of the changes and the events leading to them is Coyne, Hoskin, Pedersen 1983. (See the 'bibliography' link to the right.)

*This post first appeared in a significantly different form on 23 September 2013.

What Goes Around Comes Around

The German city of Ulm in the 16th century
Georg Braun, Franz Hogenberg 1570-78
(Click either image to enlarge.)

In the spring and summer of 1525, peasants and farmers throughout German speaking Europe staged a popular revolt now called the Deutscher Bauernkrieg. [1] At the heart of the matter was an oppressive system of taxation run by the Roman Catholic Church, in which little or none of the revenue was used to improve life locally. Often, action was lead by Protestant clergy, but to little effect against the mercenary armies hired by the aristocracy. In the end, up to 100,000 of the poorly armed and organized peasants were slaughtered.

Along the banks of the Danube River in southern Germany lies the ancient city of Ulm. Besides being the birthplace of Albert Einstein, Ulm was, in the sixteenth century, near the center of the Peasant’s Revolt, which brings us to a curious story which traces the migration of a technical recipe from Ulm over the alps to Venice, then to Sienna and finally Florence. The recipe is for the metal alloy to make mirrors, and it is told from one friend to another while chatting amiably in Venice.

Among other things, he said that he had made one [concave mirror] almost half a braccio across [about 13 inches], which extended the clear rays of its brightness more than a quarter of a German league when he caught the sun with it. One day, when for amusement he was standing in a window to watch a review of armed men in the city of Ulm, he bore with the sphere of his mirror for a quarter of an hour on the back of the shoulder armor of one of those soldiers. This not only caused so much heat that it became almost unbearable to the soldier, but it inflamed so that it kindled his jacket  underneath and burned it for him, cooking his flesh to his very great torment. Since he did not understand who caused this, he said that God had miraculously sent that fire on him for his great sins. [2]

The story was told to Vannoccio Biringuccio, who recalls it in 1540 in his Pirotechnia, the first printed book devoted to metallurgy. Specifically, the recipe is a variant of what today we would call white bronze, which as Biringuccio states is similar to the metal used to cast bells. He recites ancient formulations that used three parts copper and one part tin. To this was added 1/18th part of antimony and optionally 1/24th part of fine silver to give it a neutral color. Indeed, other ancient formulations for what was known as speculum metal specify a 3:1 ratio of copper to tin. He continues,

But nowadays most of the masters who make them take three parts of tin and one of copper, and melt these together. When they are melted, for every pound of this material, they throw in one ounce of tartar and half an ounce of powdered arsenic, and let them fume and melt and incorporate well. 

Biringuccio’s version reverses the copper and tin ratio from the classical composition. Compare it with Antonio Neri’s prescription which appears half a century later, it is almost identical:

Have 3 lbs of well-purified tin, and 1 lb of copper also purified. Melt these two metals, first the copper, then the tin. When they fuse thoroughly, throw onto them 6 oz of just singed red wine tartar, and 1½ oz of saltpeter, then ¼ oz of alum, and 2 oz of arsenic. Leave these all to vaporize, and then cast [the metal] into the form of a sphere. You will have good material, which when you burnish and polish, will look most fine. This mixture is called acciaio and is used to make spherical mirrors.

To be clear, the tartar, saltpeter and alum act as a surface flux - they form a layer that floats on the liquid metal, preventing oxides from forming, which can foul the melt.  their addition does not change the base alloy composition.

The similarity of the two recipes alone is not enough to draw any conclusions. Biringuccio himself reports that the contemporary artisans favored the tin rich formulation. However, there are other details to consider. The Sienese born Biringuccio was something of a hero in Florence where Antonio Neri was raised. The famous metallurgist helped cast cannons, mortars and guns for the Florentines to defend themselves in the late 1520s, when the city was under siege, just a few years after Biringuccio’s conversation in Venice with his German Friend from Ulm.

Neri was definitely familiar with Biringuccio’s book Pirotechnia. In fact, the introduction to Neri’s own book L’Arte Vetraria is patterned after the metallurgist’s survey of glassmaking.  In his chapter 14, book 2 Biringuccio wrote:

… it [glass] is one of the effects and real fruits of the art of fire, because every product found in the interior of the earth is either stone, metal, or one of the semi-minerals.  Glass is seen to resemble all of them, although in all respects it depends on art. [3]

And here is the opening to Neri’s introduction a half century later in 1612,

Without a doubt, glass is a true fruit of the art of fire, as it can so closely resemble all kinds of rocks and minerals, yet it is a compound, and made by art. [4]

Both passages go on to cover much of the same ground, albeit with a change in focus reflective of new thinking about chemistry and nature. In one sense, Neri is paying homage to his distinguished predecessor, and there can be little doubt that he read Biringuccio’s book and its technical recipes closely. 

In the years leading to the publication of Neri’s book, he left his home in Florence and traveled to visit a friend in Antwerp. If he had read the book on metallurgy early, perhaps as part of his education, then he was already familiar with the mirror alloy recipe. If he followed the route suggested by his friend, he would have taken the recipe back to Venice, and then over the Alps and likely through Ulm on his way north to the Low Countries, where he would spend the next seven years before returning to Italy. [5]

[1] For more on the German peasant wars of 1524-25 see https://en.wikipedia.org/wiki/German_Peasants%27_War
[2] Vannoccio Biringuccio, Pirotechnia. Ed., Tr. Cyril Stanley Smith, Martha Teach Gnudi (New York: Basic Books, 1959), pp. 385-390. (Original Italian published in 1540.)
[4] Ibid,  p.126 (in original, ff.41r-44v).
[3] Antonio Neri, L’Arte Vetraria (Florence: Giunti, 1612). p. iv.
[5] Special thanks to Jamie Hall (@PrimitiveMethod) for inspiring this post.

A Fast Calendar

A Seasons clock showing an astronomical year.
Courtesy  of  worth1000.com

Yesterday was the fourth of October. Imagine waking up this morning to discover that it is not the fifth but the fifteenth of the month; ten days have gone missing. This is exactly what happened in 1582. In accordance with a proclamation by Pope Gregory XIII, the calendar was jumped forward. The day after Thursday, 4 October, was Friday, 15 October. For the Roman Catholic world, the intervening ten days were removed from the calendar and never took place.

The seasons cycle from spring to summer to autumn to winter and back again as the earth traces its orbit around the sun. Think of this annual cycle as the dial of a watch or a clock. The dial represents the actual length of a year, when the earth returns to the same place in its orbit. Divide the face into quadrants, one for each season. Also imagine an adjustable ring showing the months along the edge of the clock face. We can then put the date system into action as a hand running around the clock. With leap-years, the then prevailing Julian system set the length of a year at 365¼ days on average. But this length of time just slightly over-ran one full rotation. This discrepancy was ignored and the date ring was, in effect reset to where the hand was after 365 ¼ days. In this way, each year the calendar began a few minutes later than the previous year. 

Like a watch that ran fast, the date system was in need of an adjustment. What forced this calendrical sleight of hand had to do with Easter. The Julian calendar with its leap year system was devised in the Roman Empire and it served admirably for many centuries. However, owing to the slight error which accumulated year after year, the calendar had advanced in the seasons by about ten days.[1] Because the date of Easter is calculated astronomically, it falls within a fixed range in the spring on the face of our clock, but because the clock was running fast, the big day fell a little earlier each year because the date ring on our clock was slowly moving forward. By the sixteenth century, Easter was falling in early March, which was not acceptable to the Church. Various gradual measures were considered to remedy the situation, but in the end, pope Gregory XIII (along with a handful of brilliant mathematicians) decided to make up for the discrepancy all at once; the ten extra days that had accumulated over the millennium were deleted from the calendar; in effect the date ring was moved backward, skipping the ten days. In addition, new rules were added for 'leap centuries'. This effectively fixed the problem by slowing the clock ever so slightly, so that on average the hand on the clock cycled extraordinarily close to an astronomical year.[2] And so the Gregorian calendar was born.

Other parts of Europe eventually adopted the changes, some sooner than others. In France, 9 December 1582 was followed by 20 December. A letter sent from Italy on November first of that year might well appear at its destination in France the last week of October, seeming to arrive before it was sent. In the Netherlands and Germany some provinces made the changes while others held out until 1700. Protestant countries did not generally adopt the new system until much later. Britain and her American colonies did not make the change until 1752 by which time the calendars were out of synchronization by a full eleven days.

When the Calendar was adjusted in Italy, Antonio Neri was six and a half years old; hardly old enough to remember the event. However, by an odd coincidence he was born on a leap year day, 29 February 1576. In any event, he must have experienced some of the stranger side effects in his adult life, especially when traveling. In making the journey to visit Emmanuel Ximenes, in Antwerp in 1604, if our priest stuck to the route suggested by his friend, he would have remained in Catholic territory until the very end of his journey. Once in the Low Countries, the date of the month would depend on the city. In Protestant controlled regions, like Utrecht, the date would suddenly jump backwards by ten days from nearby Catholic regions, although the days of the week would be consistent. Those crossing the English channel, from Calais France to Dover, for example, would experience a similar effect; it might be early May on one side and late April on the other. In such a crossing, one would experience the disconcerting 'Déjà vu' of living the same date range twice, once as Monday through Friday and then again as the following Thursday through Monday.

If there is a lesson here for close observers of nature, it is that daily living in the early seventeenth century emphasized the difference between the natural world and the contrivances of man. Subtle as it may seem to us today, April does not so much signify the rebirth of our gardens, as the rebirth of our gardens is what we have come to call April. The realignment of the calendar in 1582 emphasized this distinction, foreshadowing philosopher-scientist Alfred Korzybski's premise that "the map is not the territory."

[1] The Catholic Julian Calendar dates from the council of Nicaea in 325 CE.

[2] The authoritative reference on the full extent of the changes and the events leading to them is Coyne, Hoskin, Pedersen 1983. (See the 'bibliography' link to the right.)

*This post first appeared in a significantly different form on 23 September 2013.