Page 311 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

Thompson (1932) notes that the Italian painter and author Cennino Cennini (ca. 1370-
ca. 1440) used both lead white and verdigris to assist in the drying and consolidation of cements.
Eastlake (1847) also reports that Cennini was well aware of the siccative power of verdigris. As
the artist states:
If you wish this mordant to last [that is, to remain adhesive] for a week before gilding, put
no verdigris; f you wish it to last four days, put a little verdigris; f you wish the mordant
i
i
to be good for a day only, put much verdigris. (Eastlake 1847:136)
Additional effects of the copper acetates include activity as an antioxidant in linseed oil, a
protector of nonsaponifiable fractions of drying oils, and a drying promoter. There are many
examples of Indian miniatures, for example, that have partially deteriorated, especially in areas
where verdigris is present.

THE C O P P E R R E S I N A T E S

The dissolution of verdigris in a resin produces the so-called copper resínate pigment group.
This was a way of treating verdigris to create a good-quality green pigment. Eastlake (1847),
quoting Samuel van Hoogstraten (1627-78), remarks that satisfactory green pigments were not
as easily obtained as other pigments and that terre verte is too weak, verdigris (basic copper
acetate) too crude, and green bice (malachite) not durable.
22
When copper resínate pigments were first made is not precisely known, although they may
have been used in manuscript illumination as early as the tenth century, but this needs to be con­
firmed. Copper résinâtes were primarily used from the fourteenth to the sixteenth century; they
are not common after the end of the sixteenth century.
In his De Mayerne Manuscript of I620, the English court physician Théodore Turquet
de Mayerne (1573-1655) records the following recipe for treating verdigris to produce a good
green pigment:
Bouffault, a very excellent workman, gave me these secrets on his deathbed. A beauti­
ful green. Take of Venice turpentine two ounces, spirit of turpentine an ounce and a half,
mix them, add two ounces of verdigris, reduced to small fragments. Place these ingredients
on hot ashes, and let them gently dissolve. Try the colour on glass. Pass it through linen.
(Eastlake 1847:142)

Grinding verdigris with oil will also produce a kind of copper resínate. Eastlake provides
the following instructions for one from Liber de coloribus illuminatorum sive pictorum, a manu­
script in the British Museum (Sloane M s 1754) that probably dates from the fourteenth century:

C H A P T E R N I N E
294