Page 308 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

I VERDIGRIS RECIPES FROM ASIA AND THE MIDDLE EAST
In China, verdigris was prepared as both a pigment and a medicinal by at least the early cen­
turies B.C.E. (Needham 1974), using the familiar technique of exposing copper to the fumes of
warm vinegar. Verdigris solutions were also applied to the surfaces of wooden objects as a stain
and to prevent biodeterioration of the wood.
The following is a recipe for a synthetic blue pigment:
To get a blue pigment from copper one must mix three tean [tenths of an ounce] of the
rust of copper with seventeen tean of sal ammoniac and boil this mixture with pure
water. Hhienepann who lived n the Han Dynasty was the inventor of this pigment.
i
(Needham 1974:244)

Assuming that the rust of copper is copper (I) oxide, cuprite, this recipe was followed using 1.5 g
of cuprite and 8.5 g of ammonium chloride. The light blue-green precipitate that formed was
identified by X-ray diffraction as pure atacamite. Details of this replication experiment are
found in APPENDIX B, RECIPE 22.
Needham mentions an ancient text by Sun Ssu-Mo, who refers to coloring verdigris with
indigo to give it a bluer color. Needham calls the mineral discussed "malachite," since malachite
is green, but this may not be correct. Perhaps azurite is really implied by Sun's text. The blue
pigment described would have been useful in both fresco and scroll painting, according to
Needham (1974:136).
A Chinese text originally translated by Klaproth and discussed by Needham gives the fol­
lowing instructions for making green pigment. As mentioned in CHAPTER 3, this recipe can
actually produce chalconatronite, Na 2 Cu(C0 3 ) 2 -3H 2 0:

To get a fine green pigment from copper one must calcine the rust [to make a copper oxide]
and then boil it with white alum in a sufficient amount of water. After it has cooled it will
be green, and one must add some natron solution [a naturally occurring mixture of sodium
carbonate, sulfate, and chloride] which will precipitate the green colour called hsiao lu se.
This is used in painting for the colour of plant and bamboo leaves. (Needham 1974:32)
Bukhari (i963) discusses an Indian manuscript describing pigment recipes prepared during
the reign of Aurangzeb (16I8-1707), the last of the great Mughal emperors of India. The manu­
script, known as the Asrarul Khat, was written by Fadlu'llah Ansari wal Faruqi in 1690. Recipe 4
of this manuscript describes the production of a good quality of "zangar" (verdigris):

[recipe 4] [T]ake one rati [weight unit] of naushagar [sal ammoniac] and half rati of copper
scraps, put them in a pot and pour grape vinegar drop by drop into the vessel and with the
help of a stick, whose top should be flat, grind the admixture in the pot till it becomes zan­
gar. (Bukhari 1963 : iii)

T H E ORGANI C SALT S O F C O P P E R
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