Page 342 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

Concerning the use of metal alloys, in this case copper and iron, for their aesthetic attrib­
utes, Pliny writes of the artist Aristonidas who sought to capture in a sculpture the madness of
Athamas after he had hurled his son Learchus from a rock:
[H]e made a blend of copper and iron, in order that the blush of shame should be repre­
sented by rust of the iron shining through the brilliant surface of the copper; this statue is
still standing at Rhodes. 3

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Iron is insoluble in copper at room temperature; f present in the alloy, it will occur as small
dendrites or globules mixed with the copper grains. The equilibrium diagram is discussed by
Cooke and Aschenbrenner (1975) and by Scott (1991). It is quite possible that iron was added to
the bronze used to cast the head of Aristonidas 's sculpture. The iron would have remained unal­
loyed, or it would have been incorporated as dendritic zones; in either case, subsequent corro­
sion could produce a superficial bloom of rust on the surface of the alloy. Since small additions
of elements such as arsenic, lead, iron, and gold are closely associated with Corinthian bronzes
and are also linked with deliberate patination to produce black-colored surfaces, it is quite pos­
sible that Pliny's allusion to "a blend of copper and iron" refers to these types of bronzes (dis­
cussed in greater detail in CHAPTER 2).
Alloys of different composition were certainly recognized early as conferring a particular
color or producing a certain kind of patina. In Southeast Asia, for example, brass was known
as tombac; an alloy with a very high copper content was called hong deng; and copper alloys
with precious metals was known as samrit (Coedes 1923). The existence of a specific nomen­
clature suggests that surface coloration of these alloys was known and employed in these
regions. Within the Greek and Roman context, Pliny writes that so-called Delian bronzes (from
the Greek Island of Delos) were the first to become famous, then those from the island of
Aegina, and still later the Corinthian bronzes. These examples suffice to show that surface color
and patina were certainly important aspects of the appearance of bronze sculpture, even f the
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majority of bronzes were kept bright and polished, as Richter held.
In the Moralia Plutarch's characters muse on the different possibilities for the nature of
patina on old bronzes, wondering f the ancient masters used a certain mixture or preparation
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to achieve a particular effect. Various suggestions, some of them rather poetic, are made to
account for the presence of the patina through physical conditions: that it is due to the atmo­
sphere entering the bronze and forcing out the rust, for example, or that when the bronze gets
old it "exhales" the rust.
A Greek bronze of a type that could well have been discussed by Plutarch is the Herrn men­
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tioned earlier (see PLATE 2), which dates to 00-50 B.C.E. Plutarch was probably surprised at
the patinated appearance of old Greek bronzes such as this one; in his own time, such objects
would have retained a bronze-colored metallic sheen. Evidence in support of this includes an
Egyptian inscription from the ancient town of Chios that dates to the fourth century B.C.E. and
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S O M E A S P E C T S O F B R O N Z E PATINA S
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