Page 421 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

Recipes
A P P E N D I X β

Except as otherwise indicated, all of the following recipes
were produced by the author and coworkers at the
Getty Conservation Institute (GCI) Museum Research Laboratory.

RECIPE 1 JAPANESE PATINA FOR COPPER PATINATION
Murakami (1993) made up a series of copper alloys containing 3% gold and 97% copper for most
of the experimental work. After shaping, the alloys were polished to a mirror finish and care­
fully degreased. Traditionally, charcoal was used for the final polishing, and Japanese radish
for degreasing. The samples were boiled for 30 minutes in a solution developed by the Tokyo
National University of Fine Arts and Music. The solution contains 1.9 g of natural verdigris, 1.2 g
1
of copper sulfate, and 0.2 g of potassium aluminium sulfate in 1 of water. The pH is about 5.6.
The characteristic color of each alloy did not appear until it was boiled in the coloring solution.

RECIPE 2 CUPRITE PATINA FOR BRONZE
Socha and colleagues (i98o) obtained a cuprous oxide patina on the column of King
I
Sigismund II in Warsaw with a solution containing 5 g of ammonium persulfate, 50 g of sodium
hydroxide, and s g of mercuric chloride in 950 ml of water kept at 60 °C. This was applied for
1 hour to the cleaned metal surface in three to five operations. Between applications, the solu­
tion was mixed with sodium polysulfide (0.5 g/1) and sodium hydrogen carbonate (0.5 g/1) to
remove superfluous salts.

RECIPE 3 SYNTHETIC GEORGEITE
Pollard, Thomas, and Williams (1991) prepared georgeite by stirring 0.8 g of cupric chloride
dihydrate into a solution of 5.3 g of sodium chloride in 100 ml of water at 25 °C. A rapid reaction
ensued, forming a blue precipitate that was isolated at the pump with a Büchner funnel, washed
with water and then acetone, and dried in a vacuum over silica gel at room temperature. The
metastable georgeite precipitate recrystallized to malachite within 3 hours at 20 °C.