Historical Painting Techniques, Materials, and Studio Practice

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0

0 2 4

Co

Fe

6

Ni

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As Ph

As

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KeV

Bi

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Ph

Bi

14 16 18 20

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, Victo­
ria & 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 Ve­
netian 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 eigh­
teenth century (45). Neither the Venetian enamel nor the Basohli smalt seem

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(^450) Fe As & Ph
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Bi
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Sr
Ca
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2 4 6 8 10 12 14 16 18 20
KeV
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).
Darrah 75