DOI issue:
Sudan
DOI article:Nowicka, Anna: Analyses of pigments from the cruciform building (B.III) in Dongola
DOI Page / Citation link:https://doi.org/10.11588/diglit.41371#0215
OLD DONGOLA
SUDAN
Sample no. 12: a) yellow, b) orange, c) red
(interior plastering, second layer)
a) Microscopic observation in reflected light (x 48):
Yellow-colored layer, glimmering strongly (brocade
effect).
Microscopic observation of water smear in trans-
mitted light (x 640): Observed grains — numerous
yellow, light-colored, translucent, in the form of
hexagonal plates (more or less regular), size 0.003-
0.015 mm; yellow, semi-translucent, rounded, size c.
0.003-0.006 mm.
Solubility in acids and alkalines: 3M HC1 — no
evident reaction in cold acid, pale yellow residue left
after evaporating the sample; cone. HC1 — partly
dissolves when hot; 4M NaOH — no evident
reaction.
Fe3+ cation determination: positive.
Conclusion: The yellow layer is com-
posed of mainly a pulverized yellow mineral
— aluminosilicate characterized by mono-
clinic crystallization. The sample also
contains some iron oxide yellow. In-
strumental analysis is required to determine
the exact kind of aluminosilicate.
b) Microscopic observation in reflected light (x 48):
Heterogeneous surface of painting layer — apparent
red, yellow spots, innumerous grains shining like
microscopic mirrors.
Microscopic observation of water smear in
transmitted light (x 640): Observed grains - red
of brown and orange shade, semi-translucent, dif-
ferentiated, size 0.7-0.012 mm; yellow, differ-
entiated, rounded, semi-translucent, size most
frequently c. 0.003 mm, maximum 0.009 mm;
colorless, clear, angular breaks, size 0.01-0.03 mm
(most likely quartz); innumerous hexagonal plates,
clear, yellowish, size c. 0.004 mm (presumably
responsible for the microscopic shining spots
described above);
Solubility in acids and alkalines: 3M HC1 -
most of the sample is not dissolved; cone. HNO.
— not dissolved; 4M NaOH — no evident changes
in the sample; cone. HC1 — partly dissolves when
hot.
Pb2+ cation determination: negative; Fe3+
cation determination: positive.
Conclusion: Painting layer contains
a mixture of iron oxide red (Fe203) and
iron oxide yellow (Fe2CX nH^O). Nega-
tive result of lead cation determination
excludes addition of lead yellow. The layer
also contains an insignificant amount of
a mineral, possibly the same alumino-
silicate characterized by monoclinic
crystallization that was found in the yellow
layer of the sample (see above).
213
SUDAN
Sample no. 12: a) yellow, b) orange, c) red
(interior plastering, second layer)
a) Microscopic observation in reflected light (x 48):
Yellow-colored layer, glimmering strongly (brocade
effect).
Microscopic observation of water smear in trans-
mitted light (x 640): Observed grains — numerous
yellow, light-colored, translucent, in the form of
hexagonal plates (more or less regular), size 0.003-
0.015 mm; yellow, semi-translucent, rounded, size c.
0.003-0.006 mm.
Solubility in acids and alkalines: 3M HC1 — no
evident reaction in cold acid, pale yellow residue left
after evaporating the sample; cone. HC1 — partly
dissolves when hot; 4M NaOH — no evident
reaction.
Fe3+ cation determination: positive.
Conclusion: The yellow layer is com-
posed of mainly a pulverized yellow mineral
— aluminosilicate characterized by mono-
clinic crystallization. The sample also
contains some iron oxide yellow. In-
strumental analysis is required to determine
the exact kind of aluminosilicate.
b) Microscopic observation in reflected light (x 48):
Heterogeneous surface of painting layer — apparent
red, yellow spots, innumerous grains shining like
microscopic mirrors.
Microscopic observation of water smear in
transmitted light (x 640): Observed grains - red
of brown and orange shade, semi-translucent, dif-
ferentiated, size 0.7-0.012 mm; yellow, differ-
entiated, rounded, semi-translucent, size most
frequently c. 0.003 mm, maximum 0.009 mm;
colorless, clear, angular breaks, size 0.01-0.03 mm
(most likely quartz); innumerous hexagonal plates,
clear, yellowish, size c. 0.004 mm (presumably
responsible for the microscopic shining spots
described above);
Solubility in acids and alkalines: 3M HC1 -
most of the sample is not dissolved; cone. HNO.
— not dissolved; 4M NaOH — no evident changes
in the sample; cone. HC1 — partly dissolves when
hot.
Pb2+ cation determination: negative; Fe3+
cation determination: positive.
Conclusion: Painting layer contains
a mixture of iron oxide red (Fe203) and
iron oxide yellow (Fe2CX nH^O). Nega-
tive result of lead cation determination
excludes addition of lead yellow. The layer
also contains an insignificant amount of
a mineral, possibly the same alumino-
silicate characterized by monoclinic
crystallization that was found in the yellow
layer of the sample (see above).
213