Page 290 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

of the solution on small wooden sticks. This neutral monohydrate is the best-known salt, but
even here there are possibilities for some variation in properties. Laboratory research at the
Getty Conservation Institute showed that samples could be prepared that were either mono­
clinic or triclinic in crystal habit. APPENDIX D, TABLE 10, shows the results of a typical exper­
4
iment to make a basic verdigris by the reaction of vinegar with copper foil; it only succeeded in
producing another example of the neutral salt corresponding to ICDD 27-145. In 1998 Roy pro­
vided the GCI Museum Research Laboratory with specimens of five different verdigris salts from
the collections of the National Gallery of Art, London. Two of these corresponded to the same
5
salt produced in the previous experiment. Results of the Debye-Scherrer powder X-ray diffrac­
tion study of these samples are shown in APPENDIX D, TABLE 11.
I NEW VERDIGRIS SYNTHESES The previously published X-ray
diffraction data for the basic copper (II) acetates are sometimes contradictory and difficult to
understand. To rectify this situation, a number of new syntheses were carried out at the GCI
Museum Research Laboratory using recipes designed there, as well as recipes from Gauthier
(i958); Schweizer and Mühlethaler (i968); and Rahn-Koltermann and colleagues (1991). Histori­
cal pigment recipes were also replicated.
[
Compound A, C U ( C H 3 C O O ) 2 ] 2 - C U ( O H ) 2 - 5 H 2 0 , was synthesized using a recipe from
Gauthier (quoted in Schweizer and Mühlethaler 1968) and by Rahn-Koltermann and cowork­
ers. Two syntheses for compound A are described in APPENDIX B, RECIPE 8. Schweizer and
Mühlethaler's synthesis of compound Β is given in APPENDIX B, RECIPE 9. Two syntheses of
compound c are given in APPENDIX B, RECIPE 10. Data for additional syntheses of com­
pounds A, B, and c are given in APPENDIX D, TABLE 12. The synthesis of compound D, as well
as original recipes with samples provided by Roy, is described in APPENDIX B, RECIPE 11.
Rahn-Koltermann's group could not synthesize compound B. The author was successful,
however, in producing five different solid products that were removed at different stages of the
reaction. APPENDIX D, TABLE 13, presents the following seven data sets: the author's five prod­
ucts (labeled BI through Β 5) from the synthesis of compound B; new data for the Schweizer and
Mühlethaler version of compound B; and data for a laboratory synthesis of compound A. Judg­
ing by the X-ray diffraction data, most of these syntheses of Cu(CH 3 COO) 2 -Cu(OH) 2 -5H 2 0
produced quite similar results.
COO) [Cu (OH) 2 O, was con­
] 3
The National Gallery's sample of compound D, CU (CH 3 2 2 · H 2
firmed as being the same salt as the one derived from Schweizer and Mühlethaler's recipe.
APPENDIX D, TABLE 14, compares data for this sample with data for two syntheses (labeled ytD
and Ayt2) from the GCI Museum Research Laboratory. APPENDIX D, TABLE 15, shows the value
of this newly revised and expanded set of data: it was used to show that a light green verdigris
pigment sample from a manuscript had an X-ray diffraction pattern that was an excellent match
to the author's synthesis of compound Β (sample B4). The verdigris pigment is from Barlaam und

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