Encyclopedia of the Incas

smelted in the Americas prior to the European invasion in the^ sixteenth century.
In the Andes, copper became the primary and necessary component of almost all
the alloys developed there.
The melting together of smelted copper metal and smelted silver metal over a
wide range of proportions (by weight) of the two components, produced what
are likely the earliest alloys in the central Andes and the most important alloys
throughout Andean prehistory. Central Andean metalsmiths preferred to handle
metal as a solid, often hammering and annealing (intermittent heating) the metal
into thin sheets that they shaped and joined subsequently into three-dimensional
objects. Copper-silver alloys provided excellent solders for joining an
assemblage of thin sheets of gold or of copper. (Modern industry uses these same
solders to assemble components of electronic circuit boards.) Of greater
significance are the mechanical and physical properties that copper confers to
silver when the two metals are alloyed and shaped through mechanical means,
such as hammering. Thin sheets of copper-silver alloy are mechanically tough
(they resist fracture), maintain sufficient malleability to undergo continued
deformation and annealing to produce the final form, and they are stiff enough to
retain their shape under normal conditions of use.
The physical properties of these alloys were of equal importance to their
mechanical enhancement. For Moche smiths, color was the most salient physical
property of the metal objects they crafted. Regardless of the proportions of
copper to silver in an alloy, during the annealing of thin sheet metal, copper
atoms at the surfaces of the sheet oxidize, leaving on the surfaces a layer of
almost pure silver to confer a silver color to the sheet. In this regime, copper
within the alloy, or inside the object, provides a mechanism for transforming the
surface color of the alloy and for exhibiting that color as a key manifestation of
the object. Similarly, the Moche prepared ingots of ternary copper-silver-gold
alloys that, when rendered into thin sheet, displayed richly golden surface colors
after chemical treatments of the surfaces eliminated both the copper and silver
alloy components. These techniques are often referred to as depletion silvering
and depletion gilding—surface enrichment of culturally desired color through
depletion of selected alloy elements.
On the north coast of Peru, the Moche were followed by Sicán, and Sicán by
Chimú (see Chronology, pre-Inca). Each of these societies continued the sheet
metal, enrichment-coloring traditions established by the Moche, with increasing
production of large, shiny, elite, silver- and gold-colored objects that the Inca
encountered upon their conquest of the kingdom of Chimor ca. AD 1476. The