The Incas: Machu Picchu, Cuzco, Inca Trail

Metallurgy

Ancient Peruvian headdress dating back to AD700. The golden headdress was made in the image of an ancient sea god, making it a prized example of artwork by the Mochica civilization. The Pre-Inca Mochica or Moche civilization flourished for about 1,000 years between 200BC and AD700 on the northern coast of Peru.

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Go Geometry from the Land of the Incas

Hiram Bingham, the American explorer who found the ruins of Machu Picchu in 1911, wrote:

Inca bronze has been found to be remarkably pure, aside from very small quantities of sulphur. The proportion of copper in Inca bronze varies from 86% in some articles to 97% in others. Some archaeologists have taken the position that since the greatest quantity of tin is usually found in those bronzes that would seen to require it least, the presence of tin in Inca bronzes should be regarded as accidental. This hypotheses has been carefully considered by the experts of the largest copper companies now known that during World War II enormous quantities of tin were recovered from Bolivian mines where our manufactures were delighted to secure supplies to take the place of those that came from the Straits Settlements before the Japanese occupation. It is also well known that enormous deposits of copper are found in Peru and in Chile but not in combination with tin.

My friend Professor Charles H. Matthewson of Yale University, was the first modern metallurgist to make an exhaustive study of Inca bronzes. He discovered that the percentage of tin contained in Inca bronzes was not governed by the uses for which they requirements of the ancient methods of manufacture. Everything that we know about Inca metallurgy is based on Professor Matthewson’s report.

The Incas learned the interesting fact that bronze containing a high percentage of tin yields the best impression in casting because during the process of solidifying it expands more than bronze having a low tin content. Hence the more delicate or ornamental pieces contain the highest percentage of tin. Artistic details were thus more strikingly brought out in the finished product. Of course, had the Incas possessed steel graving tools the case would have been different. However, the Inca metallurgists learned that the operation of casting small delicate objects is facilitated when there is about ten percent of tin in the mixture. Such alloys retain their initial heat longer and so remain longer in a fluid condition. Since small objects tend to cool rapidly this knowledge was particularly useful in the manufacture of ornamental shawl-pins and ear spoons and accounts for the higher percentage of tin the Incas used in making them.


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Since these early metallurgists were unfamiliar with modern methods of heat treatment they were compelled to sacrifice the extra hardness and strength obtainable in casting axes and chisels by increasing the tin content in them. Such implements had to be frequently hammered and annealed. Since cold-working had to be depended upon to produce the final hardness of such objects, more than one heating was needed in forging the blades and this process necessitated a low tin content. Necessarily they employed a formula for combined cooper and tin which has impressed archaeologists only familiar with the chemical analysis of Inca bronzes, as being that which is unsuited for axes, chisels and large knives. It was only after a metallographic study of Inca bronzes, involving the mutilation of the pieces examined that Professor Matthewson learned the structure of such objects, the methods of their manufacture and the reasons for the variation that has been found to exist. The Inca metallurgists cast their bronze knives generally in one piece and then cold-worked them.

Such reheating as took place was solely for the purpose of softening the metal to facilitate cold-working, which was probably done at less than red heat. Some Inca bronzes are found to have been repeatedly hammered and reheated. This hammering might have been done with the stone tools with which the Incas were familiar.

The knife blades appear to have been worked and hammered so as to extend the metal more or less uniformly in several directions. Chisels and axes, on the other hand, were cast practically in the shape finally desired.


A tumi. A ceremonial knive measuring 35 cm (13.8 in.) has an engraved image of the God Sicán or Naylamp.

Archaeologists discover 1,000-year-old mausoleum in Peru. November 2006.

The Inca metallurgists were sufficiently ingenious to use more than one variety of bronze in the construction of an inverted “T” . If it was desired to ornament the of the handle with a llama’s head or attractive bird, the ornament would be made of bronze with a content of tin. The metal of the blade and the lower part of the handle on the other hand was of bronze of lower tin content because the blades had to be cold-worked.
The ornamental part of the knife handle was actually cast around the shank of the knife handle was actually cast around the shank of the knife after it had been completed. The Inca artisan, anxious to make a good serviceable knife and at the same time make it attractive, had learned over the centuries to take infinite pains in doing it. If he wished to make a hole in the end of a knife or shawl-pin, he did it in the process of casting because he lacked steel tools for drilling it.

In making bronze bolas which could be used in capturing a flying parrot or many-hued macaw, he cast the ball with a pin already in so that the cord connecting the two parts of the bolas could be securely fastened without interfering with the smooth flight of the missile. The pin was not set into the bolas but was cast in place. It must have been a great sight to see an Inca hunter bring down a flying macaw with a skillful swing of the little bronze bolas, discharging them at just the right moment to entangle its wings and legs without damaging the beautiful captive.

Some axe blades bear evidence that they were used upon stone. Their structure shows severe damage of a character which could only result from very hard usage. They were probably used in cutting square holes in ashlars and in making sharp inside corners. It is difficult to conceive of any stone tools that could have been used successfully for this purpose. Some writers have assumed that the Incas use bronze implements to a large extent in finishing their best stone work. It seems to me, however, that even their best bronze was too soft to last long in such activities. It is not likely that it was often so employed. Experiments made in our National Museum have demonstrated that patience, perseverance, elbow grease and fine sand will enable stone tools of various shapes to work miracles in dressing and polishing both granite and andesite.

However, it is reasonably certain that the Inca builders used powerful little bronze crow-bars to get those ashlars in place which were too heavy to be lifted by hand. Called champis, these bars were sufficiently strong to be used in adjusting blocks of stone weighing ten or twenty tons. In a tensile test, made under the direction of Professor Matthewson, an old Inca champi of poor quality showed an ultimate strength of 28,000 pounds to the square inch. We found by experiment with a new bronze crow-bar of the same Inca metallurgists, it had still greater strength. The Incas could have used their little crow-bars for prying into place granite blocks weighing twenty tons without damaging the champis.

Inca bronze included not only such tools as axes, knives, chisels, and crow-bars but also such domestic utensils as tweezers, shawl=pins, and large bracelets, spangles and bells. They even made ear spoons, the ends of whose handles were often decorated with figures of humming birds.


The Lord of Sipan and Pre Inca Spiderman, Gold Neckle.

Perhaps the commonest bronze articles made by the Incas were shawl-pins. Early drawings made by the Spanish conquerors show these pins were always used for fastening the front of the shoulder covering. This custom is still common in the Andes and I have noticed in many cases the head of the shawl-pins is made like a spoon. The Incas do not appear to have been familiar with spoons. The heads of their shawl-pins, which vary in length from three inches to nine inches, are very thin so that the edges were fairly sharp and appear to have been used for cutting purposes. As the Inca women were frequently occupied in spinning yarn by means of a hand spindle, or in weaving textiles, they would have found such little knives very useful and handy.

They made bronze mirrors similar to those found in ancient Egyptian tombs. They even succeeded in making a concave bronze mirror which, when polished the rays of the sun to be sufficiently concentrated on a bit of cotton as to set it on fire. One cannot help being impressed with the great skill of the Inca metallurgists and wondering how long it took them to learn this art.

They also made bronze bodkins or large needles with eyes sufficiently large to permit them to carry a fairly stout cord. Sometimes these eyes were made by flattening the head to a narrow strip, drawing this under, laying it against the shaft of the bodkin and hammering enough of the sides onto it to secure it. This process would readily have been accomplished by the use of one of the little braziers.

They made little bronze tweezers intended to take the place of the modern razor. Highland Indians seldom have any hair on their faces. The Incas were probably anxious to remove any stray hairs by means of tweezers was even known amongst the tribes of Micronesia in the Gilbert Islands before it was thought of in New York or Paris. It is evident to the observer of manners and customs that the desire for beauty parlors is nothing new under the sun.

Source:

‘Lost City of the Incas, The Story of Machu Picchu and its Builders’ by Hiram Bingham
The American explorer who found the ruins of Machu Picchu in 1911
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Hiram Bingham at Machu Picchu
The inspiration for Indiana Jones?