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These are mostly gold or a gold alloy (with copper or silver) and have been found to be largely cold hammered and sand-polished alluvial nuggets, although a few items seem to have been produced by lost wax casting. It is presumed that at least some of these items were acquired by trade from Colombia. [39]
West Mexican smiths worked primarily in copper during the initial period, with some low-arsenic alloys, as well as occasional employment of silver and gold. Lost-wax cast bells were introduced from lower Central America and Colombia during this phase, along with several classes of cold-worked ornaments and hand tools, such as needles and tweezers.
Tumbaga objects were often made using a combination of the lost wax technique and depletion gilding. An alloy of varying proportions of copper, silver, and gold (typically in a percentage ratio of 80:15:5) was cast. It was burned after removal, turning surface copper into copper oxide, which was mechanically removed.
A very important advance in glass manufacture was the technique of adding lead oxide to the molten glass; this improved the appearance of the glass and made it easier to melt using sea-coal as a furnace fuel. This technique also increased the "working period" of the glass, making it easier to manipulate.
As the name suggests, the lost-wax method is to use wax as a mold, and heat it to melt the wax mold and lose it, thereby casting bronze ware, making the model (the outer layer of the wax model is coated with mud), lost-wax (heating to make the wax flow out), pouring copper liquid to fill the cavity left by the wax model, etc.
The earliest gold metallurgy is known from the Varna culture in Bulgaria, dating from c. 4600 BC. [6] Silver, copper, tin and meteoric iron can also be found native, allowing a limited amount of metalworking in ancient cultures. [7] Egyptian weapons made from meteoric iron in about 3000 BC were highly prized as "daggers from Heaven". [8]
The earliest gold artifacts were discovered at the site of Wadi Qana in the Levant. [13] Silver is estimated to have been discovered in Asia Minor shortly after copper and gold. [14] There is evidence that iron was known from before 5000 BC. [15] The oldest known iron objects used by humans are some beads of meteoric iron, made in Egypt in ...
In this system, high-purity wrought iron, charcoal, and glass were mixed in a crucible and heated until the iron melted and absorbed the carbon. [28] Iron chain was used in Indian suspension bridges as early as the 4th century. [29] Wootz steel was produced in India and Sri Lanka from around 300 BC. [28]