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Metal–Crucible Interactions
Published in Nagaiyar Krishnamurthy, Metal–Crucible Interactions, 2023
Crucibles used for copper smelting during the Chalcolithic period were wide, shallow vessels made from the local clay, also used for domestic pottery, with melting temperatures around 1100°C. The charge was heated from the top using blow pipes (Rehren 2003). Thornton and Rehren (2009) also reported on an unusual metalworking crucible from the prehistoric site (dated to the middle of the fourth millennium BCE) of Tepe Hissar in northeast Iran. The crucible was made of steatite (Mg3(Si4O10)(OH)2). It was apparently used for the melting and alloying of arsenical copper with lead. Steatite was also used in the middle Minoan period (ca. 2000 BCE) as mould material for casting copper (Tylecote 1992). Steatite is easily carved. In those early days in history, people had the knowledge of refractory minerals and the skill to selectively incorporate these materials into crucible making depending on process need (Darling 1990; Bunch and Hellemans 2004).
Copper and copper alloys
Published in R. F. Tylecote, The Prehistory of Metallurgy in the British Isles, 2017
This now seems to have a quite simple explanation.90 When arsenical copper is heated to a hot forging temperature (800°C) some of the arsenic is lost as white fume owing to oxidation on the surface. Naturally, the smaller the artifact, the more arsenic is likely to be lost as the surface area/volume ratio increases and also the time required to make the smaller object. The volatilization of arsenic under these conditions shows itself as a white fume, and by observing the extent of this one can get some idea of the arsenic content and the amount being lost.
Copper and its alloys
Published in William Bolton, R.A. Higgins, Materials for Engineers and Technicians, 2020
Arsenical copper contains 0.4% arsenic. This increases the temperature at which cold-worked copper begins to soften from 200°C to 550°C. This type of copper was therefore widely used in steam-locomotive fireboxes and boiler tubes, and still finds use in high-temperature steam plant. It is useless for electrical purposes, however, because of the great reduction in electrical conductivity caused by the presence of the arsenic in the solid solution.
Silver and silvery alloys in Early Minoan IB Crete
Published in Materials and Manufacturing Processes, 2020
Alessandra Giumlia-Mair, Susan C. Ferrence, Philip P. Betancourt, James D. Muhly
The fact that copper depletion (or silver enrichment) was a relatively common method in Crete can also give important hints on the manufacture of objects made of arsenical copper, which is also an alloy with a silvery color. Most of the Bronze Age items made of arsenical copper contain less then 3% of arsenic[28], and this quantity is sufficient to improve the workability of the alloy and lower the porosity of castings. Nevertheless, as shown by many analyses, there are in many eastern Mediterranean contexts several examples of arsenic-rich pieces that deserve a more detailed discussion. Arsenical copper, often with high arsenic contents, appeared in the 5th millennium.[1,29–31] As discussed by Muhly[25], the impressive hoard of Nahal Mishmar with very high arsenic contents, found in a cave near the Dead Sea and dated to the early 4th millennium, must be the result of long experimentations. In roughly the same period (Late Neolithic IIA) in Greece, there are objects with high arsenic from the Tharrounia cave in Euboea.[25] Silver working and silver objects are also testified in the same area and period.