Historical Painting Techniques, Materials, and Studio Practice

Table 2. Unusual occurrences and constituents of smalt and blue enamel.
Source Accession Blue pigment Date
Number
or enamel
Minor
EDXRF Analysis
Trace
BasohJi miniature 1.5.50-1953 smalt 1660-70
1.5.51-1953 small 1660-70
I.M.87-1930 small 1730-35
I.M.88-1930 smalt 1730-35
Bundi miniature 0.379-1889 small c.I770
Venetian jug 273-1874 enamel 1472-1525
tazza 5496-1859 enamel late 15th C.
bowl C.170-1936 enamel 1521-23
bowl C. I60-1936 enamel early 16th C.
bowl 5489-1859 enamel 1500-1600
S. German oil painting C.I.A. No 3021 small 15th - 16th C.
Pb'
As Ph·
As
As
Pb'
As
As
As
As
As
KCa Fe Co Ni Cu As
KCa Mn Fe Co Ni Cu Zn Bi
KCa Fe Co Ni Ph Bi
KCa Fe Co Ni Zn Pb Bi
KCa Ti Fe Co Ni Cu As
KCa Mn Fe Co Ni Cu Zn Pb Bi Sr Sn
KCa Mn Fe Co Ni (Au) Ph Bi Sr
KCa Ti Mn Fe Co Ni Cu Ph Bi Sr
KCa Mn Fe Co Ni Cu Zn Ph As Bi Sr (So Sb)t
KCa Mn Fe Co Ni Cu (Au) Ph Bi Sr Sn Sb
Si K Fe Co Ni Pb. Bi
• lead from lead white pigment
t tin and antimony from yellow enamel applied over blue
* Courtauld Institute of Art, SEM-EDX analysis
astery of Chora (Kariye Camii), Constantinople (1325-1453 C.E.) (32, 33). It
is likely that the smalt derived from Middle Eastern and Near Eastern blue
glass.
The earliest known source of cobalt ore is Khashan, Persia; the Mesopotamians
and Egyptians probably obtained it from there. This suggests that the
ore's coloring properties were already known to the Persians. Medieval European
glass was tinted with Damascus pigment or zaffre, the Arabic name
for cobalt oxide, again suggesting a Near Eastern source (34).
Cobalt oxide, known as sulimani, was imported into China from Persia in the
Tang period; by the fourteenth century it was transported by sea from the
Persian Gulf via Sumatra. Muslim merchants residing in China influenced
ceramic designs; much of the blue and white ware was produced fo r the
Islamic market (35).
Cobalt blue glass and glaze was known from China to Western Europe and
yet throughout this period (3000 B.C.E. to ca. 700 C.E.) the most important
blue pigment was Egyptian blue, a fr it colored with copper, at its best rivaling
azurite but often appearing in paler turquoise shades. The terminal date is
circa 850 C.E. on a fresco in the church of San Clemente in Rome (36). It
seems unlikely that the secret of making Egyptian blue was lost to the
Romans during the turmoil of the Teutonic invasions, as glass and enamel
colored with copper continued to be made both in Italy and many other
countries.
In Europe there is an inexplicable hiatus in the use of blue pigments deriving
from glass from about 850 to 1490 C.E. The Venetians were making cobalt
glass by the mid-fifteenth century; the earliest references to smalt are by Leonardo
da Vinci and Perugino in the 1490s (37). It has been identified on
an altarpiece (1493) by Michael Pacher (38). Cobalt was discovered in Saxony
in the mid-fifteenth century and fully exploited by around 1520. This may
explain the greater utilization of smalt in the sixteenth century (39, 40).
Cobalt ores combine iron with nickel and/or arsenic, the latter volatilized in
the smelting process. Cobalt was also obtained from the residue in the separation
of bismuth (41). The metal oxides were fused with sand and potash
to produce zaffre (the Arabic name still being used) and sold to glassmakers.
During research on Indian miniatures, the author found smalt on one Bundi
example (ca. 1770 C.E., central India, Hindu). The pigment, not previously
identified on Indian paintings, contained cobalt, iron, nickel, and a little arsenic
(Table 2) (Plate 13).
In a later project examining miniatures from the northern Hindu states, smalt
was fo und on four miniatures from Basohli, a tiny state in the Himalayan
foothills north of Lahore (42, 43). In one example (1660-1670 C.E.), smalt
was used to paint areas of the sky and Krishna's skin; the pigment contained
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Historical Painting Techniques, Materials, and Studio Practice