Page 364 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

over them. When the colour is required to be deepened, they are smoked in burning bam­
boo leaves. There are two ways, by heat or by cold, in which other colour details are added
to the surface colour; both employ clear gum resin which has exhausted its extremely
astringent taste, compounded with melted white wax. For blue-green colour, azurite is put
in the wax, for green malachite is used, for red cinnabar is used. Wax is used most in the
heat method; for the cold method equal quantities of wax and gum resin are used; with
these blended as required they make the added colour details. For coloured protrusions
from the surface they make small amounts of salt, metal filings, and cinnabar. The mercury
colour is made by an application of mercury and tin onto the sides and edges of the vessels,
when covered with wax the colour is hidden and dulled a little in order to dupe the collec­
tor. When rubbed in the hands a stench arizes which cannot be got rid of even by washing.
Sometimes after this process is completed they bury the vessel in the ground for a year or
two; it seems then to have archaic characteristics. (Barnard 96i : 216)
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Even though the superficial appearance of the treated bronze may have been quite con­
vincing, a connoisseur would certainly have been able to detect it, especially since the craftsman
resorted to attaching artificial bronze corrosion products with wax and resin, which could eas­
ily be discovered by scraping or probing the object's surface. The use of copper sulfate, ammo­
nium chloride, and salt during the initial phases of treatment is reminiscent of modern attempts
to patínate brass and bronze objects, as described in the numerous recipes collected in Hughes
and Rowe 1982.
More insight into patina during the Ming dynasty is offered by the following commentary
from the Hsuan-lu po-lun manuscript:

[W]ith the exception of vessels maintaining the original colour of the metal, the Hsuan
period vessels contained a class with an imitation of ancient patina. They are not like the
forged products of Honan, Chin-ling, Ku-su and such places made by baking and burying.
An old bronze founder told me that the imitation of the archaic green colours on the Hsuan
bronzes was achieved by obtaining from the Royal stores broken and incomplete ancient
vessels. They selected those with the blue-green and jade-green colourings and pounded
them into a powder and dissolving this in quicksilver, threw it into the molten bronze and
melted it together. When the vessel was completed, they next applied the colours of green
patina and red cinnabar using a mixture of quicksilver and finest sand, blended with the
colours, dabbing this on to the vessel body and allowing it to soak in. The vessel was then
roasted and cooled alternately over a fierce fire up to five times and thus the green patina
colour entered deeply into the interior of the metal. Then the vessel was boiled thoroughly
in molten white wax, brushed with a coir palm-leaf brush, rubbed with cotton cloth, then
within and without, the green and red colourings stood out, and even when scraped with a
knife they did not break away. (Barnard 96i : 217)
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