Page 274 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

EGYPTIAN B L U E AND OTHER S Y N T H E T I C COPPER S I L I C A T E S

Methods of making blue were first discovered in Alexandria, and afterwards Ves tortus set up the
making of it at Puzzuoli [Pozzuoli]. The method of obtaining it from the substances of which
it has been found to consist, is strange enough. Sand and the flowers of natron are brayed together
so finely that the product is like meal and copper is grated by means of coarse files over the
mixture, like sawdust, to form a conglomerate. Then it is made into balls by rolling it in the
hands and thus bound together for drying. The dry balls are put in an earthen jar, and the jars
in an oven. As soon as the copper and the sand grow hot and unite under the intensity of the
fire, they mutually receive each others sweat, relinquishing their peculiar properties through the
intensity of the fire, they are reduced to a blue colour.— VITRUVIUS 4
The most important advance involving the copper silicates was the development of a synthetic
analog known as Egyptian blue. This is a frit—a vitreous material made by fusing a mixture
of quartz, lime, a copper compound, and an alkali flux to produce a distinctive blue color. Egyp­
tian blue frit was used as a glaze or to make small solid objects, such as a Phoenician scarab and
Egyptian seals (FIGURE 8.1) from the collections of the J. Paul Getty Museum. When powdered,
the frit became the celebrated Egyptian blue pigment extensively used in wall paintings. With
slight changes in ingredient proportions and processing of the initial mixture, the color of the
resulting frit could be altered to create Egyptian green.
Egyptian blue first appeared in Egypt during the third millennium B.C.E. and was used
extensively over the next three thousand years. Colored copper silicates were also developed in
China but much later, during the Han dynasty (206 B.C.E.-220 C.E.), when Han blue and Han
purple were used as pigments.

F I G U R E 8. 1 Small objects
made of Egyptian blue frit: two
views of a Phoenician scarab,
late sixth to fifth century B . C . E .
16.5 by 2.8 by .5 mm, showing
8
1
B
A, top, and , impression; and
an Egyptian seal from the early
sixth century B . C . E . 15. 2 by
14.0 by .8 mm, showing c, top,
8
D
and , impression. Malibu,
J . Paul Getty Museum
(83.AN.437.3 ; 8 5 . A N . 3 7 0 . 5 ) .

c D

C O P P E R S I L I C A T E S
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