Historical Painting Techniques, Materials, and Studio Practice

500
450
As
Ph
As
400
350
Fe
Co
300
Ni
250
200
150
Bi
Ph
Bi
100
50
0
0 2 4
6
8
10
12
14 16 18 20
KeV
Figure 5. EDXRF spectrum of smalt with a high arsenic content and traces if bismuth and lead.
Krishna and Girls, 1730-1735, Basohli. Spectrum prepared by David Ford, Science Group, Victoria
& Albert Museum (I.M.87-1930).
cobalt, iron, nickel, and a trace of arsenic. On another of the same date and
on two later miniatures (1730-1735 C.E.), a very different type of smalt was
fo und in the sky and Krishna's skin (Plate 14). EDXRF spectra showed a
high arsenic content with iron, cobalt, nickel, bismuth, and lead (Fig. 5). No
orpiment (arsenic) was present on these paintings.
By coincidence, the author had been analyzing a number of enameled Venetian
glass vessels (44). Blue enamel, opacified with tin oxide, occurs on
many of these objects. In a group of five, all late-fifteenth to early-sixteenth
century, the blue enamel appeared to be opacified with arsenic; bismuth and
lead were also present (Fig. 6) . Lead oxyarsenate, 3Pb3(As04)2'PbO, is said to
have first been used as an opacifier in European heavy lead glass in the eighteenth
century (45). Neither the Venetian enamel nor the Basohli smalt seem
500
450
400
Fe
As & Ph
350 Co
300
250 Bi
Bi
200
150
Ca
Sr
100
50
2 4 6 8 10 12 14 16 18 20
Figure 6. EDXRF spectrum of cobalt blue enamel with a high arsenic content and traces of bismuth
and lead. Venetian eflamelled glass bowl, 1521-1523. Spectrum prepared by David Ford, Science
Group, Victoria & Albert Museum (C. 170-1936).
KeV
Darrah 75