Historical Painting Techniques, Materials, and Studio Practice

122

;�Dr�� -�I �D'Ld�D�t �D wa�t�' __ -' r- ,, __ '-'-,

!:;

t-..

TitiabaIt n YlIOIllow .pot Adoni. on

80/51" tcrg8t. 50kV. 3. 3m".

240 acac. 11. I. 1993, AW

A.

7 L-____________________________________________________________ �

KloV 10 11 12 13

Figure 2. XRF sp ectrum of yellow area on belt of Adonis. High peaks fo r arsenic and sulphur suggest

the presence qf orpil11ent.

particles, being enclosed in the oily medium, would no longer be incompat­

ible with other pigments, as they were in the previously used tempera tech­

niques. The radiant brilliance of their color in this new medium may have

contributed to their popularity.

Ochres were used to paint the landscape, the brownish color of the dogs, and

the golden vase near Venus's seat. Yellow ochres (hydrous iron oxides) were

identified under the microscope by their optical properties and by the pres­

ence of high peaks fo r iron in the XRF spectrum.

Blue pigments. The major blue pigment used on this painting was natural

ultramarine (Fig. 1). Samples taken from the deep blue of the mountain range

appear under the microscope as pale blue, splintery particles with a low re­

fractive index (n < 1.66). In the cross section, one can see a single layer of

densely packed blue particles.

XRF of several blue areas showed high peaks fo r cobalt, potassium, and ar­

senic, strongly suggesting the presence of smalt, an artificial pigment made

from potassium-rich glass deeply pigmented with cobalt oxide and ground

to a powder. Gettens and Stout suggest that the earliest occurrence of cobalt­

colored glass in Europe may have been in the early fifteenth-century Venetian

glass industry (8). As the colorant fo r the glass, a substance called zafran is

mentioned. A recipe in a fif teenth-century treatise already mentions the prep­

aration of smalt as a smalto cilestro (9).

The source of the smalt in the Getty painting may have been Saxony or

Bohemia, where sixteenth-century glassmakers used the locally mined co­

baltite (CoAsS) and smaltite (CoAs2) minerals, which contain large amounts

of arsenic, to make smalt. The high peaks of arsenic measured by XRF, in

combination with those of cobalt, seem to indicate that cobaltite or smaltite

minerals were the source fo r the blue pigment. It is unclear whether the

zafran, or zaffer of Italian descriptions, has the same composition as the north­

ern European cobaltite. In other areas of the painting's sky, the original ul­

tramarine was scumbled over with a pale, milky blue. Examination of cross

sections of those areas shows that the pale blue consists of a layer of almost

completely discolored glassy particles.

Red pigments. Vermilion appears in Adonis's red sleeve. Its presence was es­

tablished by discovering high mercury peaks with XRF and confirmed by

Historical Painting Techniques, Materials, and Studio Practice