Page 312 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

Grind white [lead] with wine for parchment, but with oil for wood and for walls. In like
manner grind and temper green [verdigris] with oil for wood and with wine for walls, or,
if you prefer it, with oil but for books do not grind it, but suffer it to dissolve in good
and very clear white wine. (Eastlake 1847:146)
Woudhuysen-Keller and Woudhuysen (1998) replicated the de Mayerne recipe. They make
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a distinction between verdigris dissolved in pine resin, which they call "copper resínate ," and
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verdigris dissolved in a hot oil and pine resin mixture, which they call "copper resínate I,"
although any clear-cut distinction may be difficult to establish in works of art. They note that
the terminology for oils was not clear at the time de Mayerne was writing, about 1620 - 40 (Graaf
1958). Thus the Venice turpentine called for in the recipe may not have been the equivalent of
modern Venice turpentine, which is the balsam of the larch tree. It was found to be ineffective
in dissolving verdigris. The same problem was found with Strasburg turpentine, which is an
exudation from the fir tree (genus Abies).
In their replication of de Mayerne's recipe, Woudhuysen-Keller and Woudhuysen found it
simplest to omit the spirit of turpentine and to use only a pine balsam, such as Bordeaux bal­
sam, as the solvent instead of the Venice turpentine. As the verdigris dissolved, a large quantity
of colophony (rosin) was added until the solution turned clear. When the solution was heated
carefully for two hours at a temperature not exceeding 150 °C, a mossy green, glassy mass of
resínate formed. It consisted of green isotropic particles with conchoidal fracture and a refrac­
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tive index lower than 1.66. f insufficient colophony is used, undissolved verdigris particles are
seen in cross section. The copper resínate can then be ground and mixed with linseed oil, var­
nish, or spirit of turpentine.
De Mayerne also mentioned making the resínate by grinding verdigris with linseed oil and
then adding common varnish, stirring well, and decanting the clear liquid from settled impuri­
ties. Woudhuysen-Keller and Woudhuysen mixed one part of verdigris with four parts of lin­
seed oil and heated the mixture slowly to so °C. Eight parts of colophony were then added in
small lumps, 2 3 and the temperature was raised to 120 °C. This method produces a deep green
solution that, when used cold, draws threads and is difficult to spread with a brush, although it
makes a softly rounded impasto.
Laurie (1914) used the ferrocyanide test to show that the transparent greens used in the
manuscripts he studied were copper-based rather than vegetable-based greens. On one manu­
script, Laurie observed some crystalline particles that were only partially dissolved in the green,
and he determined them to be azurite. Since azurite is not readily soluble, he supposed that it
had been treated with vinegar, evaporated, and then dissolved in pine balsam, with a few par­
ticles escaping decomposition.
The first use of copper résinâtes in paintings is found in early Netherlandish and Italian
works. These paintings often show a brown discoloration at the surface due to deterioration,

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