Page 370 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

U N D E R S T A N D I N G T R E A T M E N T H I S T O R I E S

The lack of documentation has made it difficult to reconstruct exactly what was done to objects
in the past. Different treatment approaches were, of course, used for outdoor patinated bronze,
indoor patinated bronze, architectural bronze, ornamental brass, gilded bronze, archaeological
bronzes, and so on, but it is difficult to discuss these historical treatments in a systematic man­
ner due to the paucity of information. This lack of information is especially apparent when it
comes to a discussion of treatments used to conserve outdoor bronze monuments. Generally,
i
outdoor bronzes, f they were maintained at all in the late nineteenth and early twentieth cen­
turies, came under the aegis of town councils or local authorities, just as outdoor bronzes in the
city of London, for example, still do. In the United States, the National Park Service now cares
for many bronzes erected on federal property. Treatments traditionally have evolved from wash­
ing and scrubbing the bronzes to including the use of protective waxes or natural oils and resins.
Patina was not normally removed during these treatments, and the need for routine mainte­
nance and regular oiling or waxing was generally appreciated.
The typical treatment for archaeological bronzes from 1880 to 1970 was the chemical or
electrolytic removal of corrosion products. The treatment could be applied locally or, more com­
monly, by complete immersion of the bronze. The superficial cleaning of dirt from objects has
had some benefit, but museum curators were often dismayed at the appearance of bronzes that
were returned from the conservation laboratory with their green patinas stripped away. The
rationale for this kind of treatment, which frequently altered the appearance of the object quite
drastically, was to remove dangerous compounds within the corrosion crust, although the his­
torical and aesthetic issues were never properly debated within the conservation profession at
that time. Some bronzes, mostly archaeological objects, did require some form of treatment to
avoid the risk of bronze disease, which could reduce them to a heap of green powder, but there
appeared to be little testing of the bronzes to ascertain if, indeed, treatment was really necessary
Objects not at risk were relegated to the same treatment for the disease as those with chronic
cases, with the result that healthy bronzes were needlessly stripped of their patinas.

SOME PAST C O N S E R V A T I O N T R E A T M E N T S
Patina-stripping techniques Many approaches to the conservation of bronzes during the
nineteenth or first half of the twentieth century employed
chemical or electrochemical treatments that resulted in wholesale patina removal, with the
result that bronzes might be stripped back to an oxidized-looking brown or variegated golden
metallic surface, which often represented substantial loss of original surface or associated mate­
rial. An example of this treatment approach is that of the Egyptian cat shown in PLATE 8i. The
surface was left in a raw and unappealing state following the chemical cleaning procedure.

C O N S E R V A T I O N T R E A T M E N T S F O R B R O N Z E O B J E C T S
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