Patio process
Encyclopedia
The patio process was a process used to extract silver
from ore
. The process was invented by Bartolomé de Medina in Pachuca
, New Spain
(Mexico
), in 1554. The patio process was the first process to use mercury
amalgamation to recover silver from ore. It replaced smelting as the primary method of extracting silver from ore in Spanish America. Other amalgamation processes were later developed, importantly the pan amalgamation
process, and its variant, the Washoe process.
, prohibiting the enslavement of Indians, had resulted in higher labor costs as miners turned to wage labor and expensive African slaves. These higher production costs made mining and smelting anything but the highest grade silver ores prohibitively expensive, just as the availability of high grade ores was in decline. Bartolomé de Medina initially focused his attentions on learning about new smelting methods from smelters in Spain. He was approached during his research by an unknown German man, known only as "Maestro Lorenzo," who told him that silver could be extracted from ground ores using mercury and a salt-water brine. With this knowledge, Medina left Spain for New Spain (Mexico) in 1554 and established a model patio refinery in order to prove the effectiveness of the new technology. Medina is generally credited with adding "magistral" (a copper sulfate) to the mercury and salt-water solution in order to catalyze the amalgamation reaction. However, some historians assert that there were already sufficient copper sulfates in the local ores and that no additional magistral was needed. Regardless of whether or not Medina's contribution was entirely original, he promoted his process to local miners and was able to obtain a patent from the Viceroy of New Spain. As a result, he is generally credited with the invention of silver amalgamation in the form of the patio process.
, water, magistral (essentially an impure form of copper sulfate), and mercury, and spread in a 1-to-2-foot-thick (0.30 to 0.61 m) layer in a patio
, (a shallow-walled, open enclosure). Horses were driven around on the patio to further mix the ingredients. After weeks of mixing and soaking in the sun, a complex reaction converted the silver to native metal, which formed an amalgam
with the mercury and was recovered. The amount of salt and copper sulfate varied from one-quarter to ten pounds of one or the other, or both, per ton of ore treated. The decision of how much of each ingredient to add, how much mixing was needed, and when to halt the process depended on the skill of an azoguero (English: quicksilver man). The loss of mercury in amalgamation processes is generally one to two times the weight of silver recovered.
The patio process was the first form of amalgamation. However, it is unclear whether this process or a similar process—in which amalgamation occurred in heated vats rather than open patios—was the predominant form of amalgamation in New Spain, as the earliest known illustration of the patio process dates from 1761. There is substantial evidence that both processes were used from an early date in New Spain, while open patios were never adopted in Peru
. Both processes required that ore be crushed and refiners quickly established mills to process ore once amalgamation was introduced. By the seventeenth century, water-powered mills became dominant in both New Spain and Peru.
Due to amalgamation's reliance upon mercury, an expansion of mercury production was central to the expansion of silver production. From shortly after the invention of mercury amalgamation to the end of the colonial period, the Spanish crown maintained a monopoly on mercury production and distribution, ensuring a steady supply of royal income. Fluctuations in mercury prices generally resulted in corresponding increases and decreases in silver production.
While a number of factors resulted in the minimal use of forced Indian labor in Mexican silver production, the introduction of silver amalgamation allowed for an expansion of silver production in Peru that had profound consequences for Peru's native population. Francisco Toledo, the Viceroy of Peru in the 1570s, saw amalgamation as the key to expanding Peruvian silver production. He encouraged miners to adopt amalgamation and construct mercury mines. More significantly, in order to provide sufficient labor to accommodate the expansion of silver mining to lower-grade ores, Toledo organized an Indian draft labor system, the mita. Under this system, thousands of natives were forced to work in silver and mercury mines for less than subsistence-level wages. Twelve thousand draft laborers regularly worked at the largest mine in the Americas, located at Potosí
in modern Bolivia. Native attempts to avoid the mita led to the abandonment of many Indian villages throughout Peru. Spanish monopolization of refining through amalgamation cut natives out of what had earlier been a native-dominated enterprise. Refining represented the most profitable segment of silver production. In conjunction with the mita, the exclusion of natives from owning refineries contributed to the transformation of Peruvian natives into a poorly paid labor force.
The rapid expansion of silver production and coinage—made possible due to the invention of amalgamation—has often been identified as the primary driver of the price revolution
, a period of high inflation lasting from the sixteenth to early seventeenth-century in Europe. Proponents of this theory argue that Spain's reliance on silver coins from the Americas to finance its large balance of payments deficits resulted in a general expansion of the European money supply and corresponding inflation. Critics of the theory, however, argue that inflation was really a result of European government policies and population growth.
While the role of the expansion in silver production in the price revolution may be disputed, this expansion is often acknowledged as a key ingredient in the formation of early-modern world trade. Spanish American production fed Chinese demand for silver, facilitating the development of extensive trade networks linking Europe, Africa, Asia, and the Americas as Europeans sought to gain access to Chinese wares.
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
from ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
. The process was invented by Bartolomé de Medina in Pachuca
Pachuca
Pachuca, formally Pachuca de Soto is the capital of the Mexican state of Hidalgo. It is located in the south-central part of the state. Pachuca de Soto is also the name of the municipality of which the city serves as municipal seat...
, New Spain
New Spain
New Spain, formally called the Viceroyalty of New Spain , was a viceroyalty of the Spanish colonial empire, comprising primarily territories in what was known then as 'América Septentrional' or North America. Its capital was Mexico City, formerly Tenochtitlan, capital of the Aztec Empire...
(Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
), in 1554. The patio process was the first process to use mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
amalgamation to recover silver from ore. It replaced smelting as the primary method of extracting silver from ore in Spanish America. Other amalgamation processes were later developed, importantly the pan amalgamation
Pan amalgamation
The Pan amalgamation process is a method to extract silver from ore, using mercury. The process was widely used from 1609 through the 19th century; it is no longer used....
process, and its variant, the Washoe process.
Development of the patio process
Bartolomé de Medina was a successful Spanish merchant who became fascinated with the problem of decreasing silver yields from ores mined in Spanish America. By the mid-sixteenth century, it was well known in Spain that American silver production was in decline due to the depletion of high-grade ores and increasing production costs. The New LawsNew Laws
The New Laws, in Spanish Leyes Nuevas, issued November 20, 1542 by King Charles V of Spain regarding the Spanish colonization of the Americas, are also known as the "New Laws of the Indies for the Good Treatment and Preservation of the Indians", and were created to prevent the exploitation of the...
, prohibiting the enslavement of Indians, had resulted in higher labor costs as miners turned to wage labor and expensive African slaves. These higher production costs made mining and smelting anything but the highest grade silver ores prohibitively expensive, just as the availability of high grade ores was in decline. Bartolomé de Medina initially focused his attentions on learning about new smelting methods from smelters in Spain. He was approached during his research by an unknown German man, known only as "Maestro Lorenzo," who told him that silver could be extracted from ground ores using mercury and a salt-water brine. With this knowledge, Medina left Spain for New Spain (Mexico) in 1554 and established a model patio refinery in order to prove the effectiveness of the new technology. Medina is generally credited with adding "magistral" (a copper sulfate) to the mercury and salt-water solution in order to catalyze the amalgamation reaction. However, some historians assert that there were already sufficient copper sulfates in the local ores and that no additional magistral was needed. Regardless of whether or not Medina's contribution was entirely original, he promoted his process to local miners and was able to obtain a patent from the Viceroy of New Spain. As a result, he is generally credited with the invention of silver amalgamation in the form of the patio process.
Basic elements of the patio process
Silver ores were crushed (typically either in "arrastras" or stamp mills) to a fine slime which was mixed with saltSalt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
, water, magistral (essentially an impure form of copper sulfate), and mercury, and spread in a 1-to-2-foot-thick (0.30 to 0.61 m) layer in a patio
Patio
A patio is an outdoor space generally used for dining or recreation that adjoins a residence and is typically paved. It may refer to a roofless inner courtyard of the sort found in Spanish-style dwellings or a paved area between a residence and a garden....
, (a shallow-walled, open enclosure). Horses were driven around on the patio to further mix the ingredients. After weeks of mixing and soaking in the sun, a complex reaction converted the silver to native metal, which formed an amalgam
Amalgam
Amalgam may refer to:* Amalgam , mercury alloy* Amalgam , material of "silver" tooth fillings* Amalgam Comics, publisher* Amalgam, Gauteng, South Africa* Amalgam , fictional character in the Marvel Universe...
with the mercury and was recovered. The amount of salt and copper sulfate varied from one-quarter to ten pounds of one or the other, or both, per ton of ore treated. The decision of how much of each ingredient to add, how much mixing was needed, and when to halt the process depended on the skill of an azoguero (English: quicksilver man). The loss of mercury in amalgamation processes is generally one to two times the weight of silver recovered.
The patio process was the first form of amalgamation. However, it is unclear whether this process or a similar process—in which amalgamation occurred in heated vats rather than open patios—was the predominant form of amalgamation in New Spain, as the earliest known illustration of the patio process dates from 1761. There is substantial evidence that both processes were used from an early date in New Spain, while open patios were never adopted in Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
. Both processes required that ore be crushed and refiners quickly established mills to process ore once amalgamation was introduced. By the seventeenth century, water-powered mills became dominant in both New Spain and Peru.
Due to amalgamation's reliance upon mercury, an expansion of mercury production was central to the expansion of silver production. From shortly after the invention of mercury amalgamation to the end of the colonial period, the Spanish crown maintained a monopoly on mercury production and distribution, ensuring a steady supply of royal income. Fluctuations in mercury prices generally resulted in corresponding increases and decreases in silver production.
Broader historical significance
The introduction of amalgamation to silver refining in the Americas not only ended the mid-sixteenth century crisis in silver production, it also inaugurated a rapid expansion of silver production in New Spain and Peru as miners could now profitably mine lower-grade ores. As a result of this expansion, the Americas became the primary producer of the world's silver, with Spanish America producing three-fifths of the world's silver supply prior to 1900.While a number of factors resulted in the minimal use of forced Indian labor in Mexican silver production, the introduction of silver amalgamation allowed for an expansion of silver production in Peru that had profound consequences for Peru's native population. Francisco Toledo, the Viceroy of Peru in the 1570s, saw amalgamation as the key to expanding Peruvian silver production. He encouraged miners to adopt amalgamation and construct mercury mines. More significantly, in order to provide sufficient labor to accommodate the expansion of silver mining to lower-grade ores, Toledo organized an Indian draft labor system, the mita. Under this system, thousands of natives were forced to work in silver and mercury mines for less than subsistence-level wages. Twelve thousand draft laborers regularly worked at the largest mine in the Americas, located at Potosí
Potosí
Potosí is a city and the capital of the department of Potosí in Bolivia. It is one of the highest cities in the world by elevation at a nominal . and it was the location of the Spanish colonial mint, now the National Mint of Bolivia...
in modern Bolivia. Native attempts to avoid the mita led to the abandonment of many Indian villages throughout Peru. Spanish monopolization of refining through amalgamation cut natives out of what had earlier been a native-dominated enterprise. Refining represented the most profitable segment of silver production. In conjunction with the mita, the exclusion of natives from owning refineries contributed to the transformation of Peruvian natives into a poorly paid labor force.
The rapid expansion of silver production and coinage—made possible due to the invention of amalgamation—has often been identified as the primary driver of the price revolution
Price revolution
Used generally to describe a series of economic events from the second half of the 15th century to the first half of the 17th, the price revolution refers most specifically to the relatively high rate of inflation that characterized the period across Western Europe, with prices on average rising...
, a period of high inflation lasting from the sixteenth to early seventeenth-century in Europe. Proponents of this theory argue that Spain's reliance on silver coins from the Americas to finance its large balance of payments deficits resulted in a general expansion of the European money supply and corresponding inflation. Critics of the theory, however, argue that inflation was really a result of European government policies and population growth.
While the role of the expansion in silver production in the price revolution may be disputed, this expansion is often acknowledged as a key ingredient in the formation of early-modern world trade. Spanish American production fed Chinese demand for silver, facilitating the development of extensive trade networks linking Europe, Africa, Asia, and the Americas as Europeans sought to gain access to Chinese wares.