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Table 8: Common names used to describe copper alloys for bronze sculpture

Table 8
Table 8
Common names used to describe copper alloys for bronze sculpture
As determined by eighteen CAST:ING group members, who include specialists in a wide range of disciplines and fields. Their agreement or disagreement on nomenclature is reported through the percentage of people using a given name. The preferred names of the author are reported in the gray cells. Arsenical bronzes, aluminum bronzes, and more exotic alloys such as copper-antimony, cupro-nickel, and tumbaga are not reported since they are rarely if ever used in bronze sculpture. For exotic prehistoric and historic copper alloys, see . The author wishes to recognize the contributors to this table, namely J. Bassett, A. Boulton, M. Castelle, P. Dandridge, L. Garenne-Marot, J. Kreutner, A. Lacey, S. La Niece, E. Lebon, B. Mille, L. Morigi, P. Motture, D. Reid, D. Robcis, D. Strahan, S. Sturman, and the late J.-M. Welter. All contents in weight %.
Type Name Description Most common compositions (weight %) Comment Agreement among the 17 CAST:ING specialists (%)
copper copper copper with no intentionally added elements various (see comment) Various definitions depending on the CAST:ING member: <1% Sn, <1% Pb, >95% Cu, or an alloy with ≤3% of Sn, Zn, and/or Pb, may be called copper. The 1% threshold is definitely arbitrary. 71
<1% Sn, <1% Pb 6
impure copper >96% Cu, <1% Sn, <1% Zn, <2% Pb   6
low alloyed copper copper with minor addition of other elements >95% Cu   6
mixed copper copper with minor addition of other elements >92% Cu, 1–2% Sn, 1–2% Zn rarely used 6
bronze bronze copper alloyed with tin 5–13% The minimum amount of tin for an alloy to be called bronze is difficult to state (see “”). In the literature devoted to bronzes (sculpture and other implements), it is rare to encounter a bronze with <5% Sn. 76
low-tin bronze copper alloyed with small amounts of tin 5–8% Sn This designation has been suggested by 20% of the members, yet they do not agree on the definition. For some, it should hold <5% Sn, for others, 5–8%. 6
<5% Sn 6
2–7% Sn 6
medium-tin bronze copper alloyed with moderate amounts of tin 8–15% Sn   6
7–14% Sn   6
high-tin bronze bronze with high tin from 12–15% Sn (depending on the author) to ≥25% Sn Typical alloys for bells, but encountered in sculptures as well (India, Southeast Asia, etc.). 76
bell metal copper-tin alloy with tin >15% >15% Sn   12
brass brass copper alloyed with zinc 5–15% Zn The minimum amount of zinc for an alloy to be called brass is difficult to state. In the literature devoted to bronzes (sculpture and other implements), it is rare to encounter a brass with <6–7% Zn. 65
low-zinc brass copper alloyed with small amounts of zinc 5–10% Zn This designation has been suggested by one-third of the members. Yet whereas there is consensus on the minimum content (5% Zn), the maximum content varies from 15% to 30% according to the member. 6
5–30% Zn   18
2–7% Zn   6
medium-zinc brass copper alloyed with moderate amounts of zinc 10–20% Zn   6
high-zinc brass brass with large amounts of zinc >30% Zn   24
15–30% Zn   53
>20% Zn   6
>14% Zn   6
latten   Zn as the primary alloying element, with <1% Sn and <1% Pb   12
ternary alloys gunmetal copper alloyed with zinc and tin 4–8% Sn, 4–8% Zn This term is widely used in the literature, yet it can be anachronistic, as guns did not appear before the Late Middle Ages. Some authors prefer “red brass.” See also comment in “bronze.” 24
red brass copper alloyed with zinc and tin 4–8% Sn, 4–8% Zn See comments for “gunmetal” and “bronze.” 24
leaded alloys leaded alloy any copper alloy with lead added 3–10% Pb Same comment as for brass regarding the minimum amount of lead. 65
Bronze and brass alloys with a Pb concentration of ≥4%, and Cu alloys with a Pb content of ≥2%, are described as “leaded.” 6
low-lead alloys any copper alloy with small amounts of lead added <1% Pb   6
high-lead alloy any copper alloy with large amounts of lead 15–30% Pb   41
>10% Pb   6
quarternary alloy quarternary alloy any copper alloyed with tin, zinc, and lead   Easy way to describe an alloy containing tin, zinc, and lead as intentionally added elements without having to decide on a specific name. 24
arsenic arsenical copper or arsenical bronze any copper alloy containing high amounts of arsenic 1–3% As   18
contemporary alloys silicon bronze copper alloyed with silicon ≤5% Zn Welds easily, but difficult to chase and patinate. 12
3.5–4.5% Si, 0.5% Mg, 0.5% Fe Developed around the 1880s–90s, silicon bronze was first used for the underwater telegraph cables connecting the UK to the continent. Silicon adds ductility to the alloy and lowers the viscosity of the melt, while magnesium and iron remove oxygen from the melt. 6
silicon brass copper alloyed with silicon and zinc >5% Zn   6
phosphor bronze bronze with phosporous added intentionally 0.5–11% Sn Developed around the 1880s–90s, phosphorus increases wear resistance and helps remove oxygen from the melt. 6