Page 347 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

attempt to conceal poor quality workmanship (Hughes and Rowe 1982). The available evidence,
however, suggests that this approach to surface color was less common than that of applying
reddish or pellucid patina finishes.

Other coatings on It is difficult to determine the original surface appearance of
Renaissance bronzes most Renaissance bronzes since they have often been recoated
several times over the life of the object. Some sculptures from
this period may have been originally colored red, brown, opaque gray, or black. This range
of color was used skillfully by such artists as Andrea Briosco (Riccio) (1470-1532), Jacopo
Sansovino (i486-1570), and Baccio Bandinelli (1493-i56o). Giovanni Fonduli (ca. 1430-ca.
1485-97), Francesco Susini (act. 1635-46), and Antico (Pier Jacopo Alari Bonacolsi) (ca. 1460-
1528) all used translucent red, which was greatly admired. There is a considerable variety of pos­
sible appearance for these kinds of translucent, principally organic resins or varnishes, which
are applied to a surface for reflectivity and to augment the color of the patina. Bewer (i996)
reports that most of the bronzes in the Museo e Gallerie di Capodimonte in Naples were coated
with an opaque black layer many years ago. Bewer also provides evidence that the surfaces of
the bronzes in the studiolo of Francesco I de' Medici (1541- 87) in the Palazzo Vecchio in Flor­
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ence were recoated only a few decades after the sculptures were installed.
Recent analyses of surface coatings on a small selection of fifteenth- and sixteenth-century
bronzes were made by Stone, White, and Indictor (1990). Some drying oils and turpentine
could be identified, but there were other coatings with polymeric copper-containing sub­
stances that could not be readily identified by Fourier transform infrared spectroscopy,
gas chromatography-mass spectrometry, or pyrolysis-gas chromatography-mass spectrome­
try. This is a common problem once copper cations start to interact with organic polymers —
crosslinking and degradation, chain-scission, and complexation make it difficult to identify
autochthonous components.
More humble techniques, such as long- and shortwave ultraviolet illumination, can be
of assistance in examining more recent restorations of patina involving wax or other coatings of
resin or varnish. The majority of Renaissance bronzes were waxed to seal and finish the patina
and are routinely rewaxed as part of their normal maintenance. Beeswax was commonly used
for this purpose, as well as linseed oil and lavender oil (Hughes and Rowe 1982). This tradition
is still extant; during a visit to a church in Venice, Bewer (i996) found a sixteenth-century sculp­
ture being literally immersed in linseed oil. When examined under ultraviolet light, most sculp­
tures manifest only a bluish glow from thick accumulations of wax. In one case, however, Bewer
found that Saturn Devouring a Child, a bronze attributed to Simon Hurtrelle (i648-i724) in the
collections of the J. Paul Getty Museum, gave a distinctive orange glow from the presence of
shellac on the wings and drape of the sculpture.

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