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Gilded gifts for the gods.

The small golden figures bear a roughly human form, their features sketched with tiny filaments and dots of metal. One may wear a broad headdress, another may carry a cup, still another may bear a complicated necklace. Each one is unique, yet few are elaborate. Their simplicity is haunting. Stripped to the essential elements of physical description, they draw strength from their directness, power from their elemental expression.

The figures are called tunjos. They are the primary surviving metalwork of the Muisca people, who occupied the highlands of the modern departments of Cundinimarca and Boyaca in Colombia from approximately 800 A.D. until 1537. In the fateful year, their lands were subjugated by three Spanish armies searching for the legendary El Dorado. Since the Spanish Conquest, tunjos have come to light in unlikely places--at the bottoms of lakes and lagoons, buried inside ceramic jars in caves or hillsides.

Today the figures are scattered in museums and private collections around the world. Perhaps the finest are found in the Gold Museum of the State Bank in Bogota. Over the years, a few researchers have sought to characterize the metallurgy involved in producing tunjos to uncover clues about Muisca materials and techniques.

It has long been clear that tunjos were cast using the "lost wax" technique. The artist would build a model entirely in wax, then form a clay coating around it, leaving holes or "gates" to pour in molten metal. The mold was then fired, burning away the wax, and once cooled, filled with molten metal that assumed the shape of the wax model. But it has not been clear how the Muiscas fashioned certain details often found on tunjos--free-hanging rings and what appears to be filigree work, for example.

A soon-to-be-published study by the Research Laboratory of the Museum of Fine Arts in Boston throws new light on some questions about Muisca goldwork. Laboratory researchers have become the detetives of the art world, seeking to establish provenance for works of art and to analyze materials and techniques used to create them.

"Because tunjos have not been extensively studied as artifacts from a technical point of view," says Richard Newman of the Museum's research staff, "we were interested in doing a compositional analysis and looking at the manufacturing techniques. We also wanted to settle a long-standing question about whether any surface enrichment techniques had been used."

The Museum of Fine Arts tunjo collection contains 59 figures, presented to

the museum as a gift in the 1970s from a larger collection assembled in Colombia early in the 20th century. Newman examined 21 of the prices in detail with the most modern equipment available.

"We took little metal samples, usually less than a millimeter in size, and prepared metallographic sections," he explains. While the idea of cutting away material from an artifact may seem abhorrent, it is a common practice to perform compositional analysis. Modern instruments such as the electron microscope require such small samples that the damage is invisible to the naked eye. Because tanjos are typically very thin--much less than a millimeter--Newman was able to take cross-sectional samples and examine the metal from front to back of each figure.

An identification of the metals present in all the Museum's tunjos was made by bombarding them with X-rays and then observing how the objects emitted X-rays on their own. Each metal has its own X-ray signature. Newman found only three metals--copper, gold and small amounts of silver. The silver, he suggests, was an accidental inclusion, since natural gold deposits always contain at least a small percentage of silver. Further analysis showed that the percentage of copper in the museum's tunjo collection varied from as much as 90 percent to as little as 40 percent.

Finding these alloys was not a surprise, since gold alloyed with copper, silver, platinum and other metals is widely known in Pre-Hispanic South American objects. However, the Muiscas were apparently unique in using the particular compositions--and they probably employed them for practical reasons.

Although they were renowned goldsmiths, the Muisca homeland did not contain gold; they had to trade with their neighbors to acquire the precious metal. Moreover, pure gold has a very high melting point that is hard to reach without using a charcoal-fueled bellows forge to boost temperatures--a tool the Muiscas lacked. By mixing gold and copper, the gold goes further and the alloy melts at a lower temperature than either metal alone.

Archaeologists and art historians have disagreed about whether the Muiscas nade their figures by casting alone or whether they had some other technique to attach decorations to the cooled castings. The electron microscope reveals that the crystalline structure characteristic of cast metal extends right through the body of the tunjo into the adornments. Apparently free-hanging rings were cast in place and then snapped free when the figure was cool.

Newman's research also settles a long-standing dispute among scholars over whether the Muiscas altered the surfaces of their tunjo castings. One school argued that since the figures were never polished--indeed, many still show mold marks--then it was unlikely that an artisan would have bothered with any other surface improvements. But many tunjos have surfaces that look "brassy" and even porous to the naked eye. Those characteristics often signal the use of a common technique among Pre-Hispanic South American artisans working in gold alloys--"depletion gilding."

Copper is a highly reactive metal, whereas gold is not. As a result, an object formed from a copper-gold alloy that is placed in a salty or acid solution will undergo changes. The copper will react with the salt or acid and can be washed away, leaving behind the gold. But when the copper is removed, nothing takes its place. Sure enough, the surfaces of several tunjos Newman examined showed the porosity typical of depletion gilding. Analysis with the electron microprobe confirmed it. Although the pitted surface of some pieces was almost pure gold, the copper content rose rapidly just below the surface. The external gold was typically only 1/100 of a millimeter thick.

It is now clear that the Muiscas did not use a set ratio of gold to copper in their alloys, although the presence of depletion gilding does sugges that they valued a golden appearance even for pieces that contained more copper than

gold. Moreover, the absence of any technique other than lost-wax casting suggests that the Muiscas may not have been practicing the most advanced technologies of the era, but that they were extraordinarily skilled in the techniques they did use.

Their reputation among their neighbors as master artisans in gold may have been based on another whole category of public art and adornment, examples of which have long since been melted down. But the tunjos deserve to be judged separately on the basis of technique applied to private, religious art.

The great Spanish archaeologist, Jose Perez de Barradas, contends that tunjos show a consistent style that deliberately departs from realism to express the essence of the subject without distraction. The human body is inevitably reduced to a minimum of line and form, yet each piece possesses an individual character. Perez notes that no human figures made in metal in Muisca style appear to be dressed, although the bodies are often adorned with belts and rings and carry simple objects. Their nudity conforms with the few details of Muisca religious life passed down through the chronicles.

Although the Muiscas had a pantheon of gods identified with the sun, moon and earth, they also held certain places sacred--lakes, lagoons, caves, grottoes and perhaps certain wooded sites. At these spots the priests established sanctuaries, known only to them. A Muisca who wished to ask a favor of the spirits, or give thanks for a favor granted, would commission the production of a tunjo as an offering. He then approached a priest to intercede with the spirit. Little about the ceremonies has survived, but they seem to have called for a period of fasting and the offering of the tunjo by a naked priest at one of the Muisca shrines. It is thought that the priest placed the tunjo into a ceramic jar at the site--a practice consistent with the condition of the surviving pieces.

Thus was the fate of the tunjos sealed. They were lost from sight of their makers, yet saved for modern eyes. The Musicas, a people long silent, speak to us still through the golden forms of their prayers.

Patricia Harris and David Lyon are freelance writers living in Cambridge, Massachusetts.
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Title Annotation:analysis of prehistoric gold Colombian religious relics
Author:Harris, Patricia Roberts; Lyon, David
Publication:Americas (English Edition)
Date:Sep 1, 1990
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