Page 307 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

MS 992 gives the following recipe for the manufacture of an ink:

[recipe 69] To write green letters—Take strong vinegar, powdered gum arabic, verdigris,
and roch alum, all at discretion, mixed with the juice of rue, and made so liquid that the
mixture will flow like ink. (Merrifield 1849:678).

Distilled verdigris was used to duplicate this recipe, along with white wine vinegar, pow­
dered alum, and a solution of gum arabic. The mixture produced a green liquid that could be
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painted on card, and it clearly produced a brighter green color than verdigris alone. Juice of
rue would add to the solubilization of the mixture because the porphyrin ring structure of the
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chlorophyll in the plant juice could replace copper for magnesium in the complex. This would
help to make a brighter green ink for manuscript lettering. Because the product is so complex, it
is very difficult to determine f the concoction had been used for green lettering on manuscripts.
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The following recipe was not reproduced during the author's investigations. The rationale
behind the formula is difficult to understand, and the presence of quicksilver and of the need to
grind it with other ingredients makes it potentially hazardous:

[recipe 74] A most beautiful green for miniature painting—Take equal quantities of verdi­
gris, litharge of gold, and quicksilver, grind them all to a fine powder with urine, and put
them into a botde, which you must bury in horse dung for 20 days; then take it out, grind
the verdigris again, and you will have a most noble green for miniatures, writing, and paint­
ing. (Merrifield 1849:680).

In the recipe that follows, the verdigris starting material, which was probably impure, is
first converted to the neutral salt by dissolution in vinegar:

[recipe 82] To make a green for miniatures and painting—Take verdigris, dissolve it in vine­
gar, and when it is well dissolved strain it through a fine cloth; then grind it up well on the
porphyry slab with clear water, adding honey during the grinding. Let it dry, and again
grind it up with gum water, and it will be done. (Merrifield 1849:682)
Grinding the mixture with honey produces a complex product of copper salts of sugars. This was
probably mixed with some neutral verdigris, depending on the quantities of the ingredients used.
The following recipe from M s 992 is for verdigris. A replication experiment for this account
is described in APPENDIX B, RECIPE 21.

[recipe 130] To make verdigris —Take pieces of copper anointed with purified honey, and
fasten them to the cover of a well glazed pot, which must be full of hot vinegar made with
strong wine; then cover it and place it in a warm situation for 4 or 5 weeks, and when you
uncover it, remove the colour which you find on the pieces of copper, and it will be most
beautiful. (Merrifield 1849:706)

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