Page 213 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

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PLATE 40 Scanning electron photomicrograph of a
concretion on a leaded brass nail from the Rapid site (see
PLATE 39), showing a variety of copper sulfides, princi­
pally covellite and chalcocite, together with lead sulfides,
wood remnants, and calcite (width of photomicrograph =
1000 μιη). Western Australian Maritime Museum (reg.
no. RPI812).

PLATE 41 Detail of a fourteenth-century bronze trumpet.
Close-up of the soldered join shows the surface immedi­
ately after excavation from the river Thames in 1983. The
yellow metal surface is revealed with occasional patches
of tenacious black copper sulfides.
PLATE 42 Roman coin excavated in 1986 from the water­
front area of the river Thames. Partial cleaning revealed
a top skin of chalcopyrites overlying a black powdery
layer of copper sulfides directly over the bare metal sur­
face, an extraordinary example of this type of corrosion.
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PLATE 43 Medieval copper-alloy key excavated in 1981
from waterfront area of the river Thames. Botryoidal
chalcopyrite corrosion overlies black copper sulfides with
metal beneath.

PLATE 44 Polarized-light photomicrographs of a
mounted sample of libethenite from the type site of
Libethan, Hungary: A, viewed with plane polarized illu­
mination; and Β, viewed with crossed polars at 85°
(magnification χ347).

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