CERAMIC DECORATION—FRANCHET. 641 
be sprinkled with the clay. Over the engobe may be applied the 
colored pigments. Decoration by engobage was practiced in the 
most ancient times, but no race took such a remarkable part in its 
development as the Greeks and Etruscans, who produced the great- 
est artists ever known in the art of fired pottery. 
From a technical point of view the only feature that demands 
attention here is the fact that they had the skill to introduce into 
these engobes materials sufficiently fusible to give a true glaze to the 
work, and that with only three colors—red, brown, both iron colors, 
and manganese black—they have inscribed on their vases the entire 
history of ancient Greece. 
The Greeks have always been our teachers in the practical utiliza- 
tion of ceramic decoration. Their most ancient pottery, it is true, 
bear only elementary designs painted with colored clays, but little 
by little there appeared representations of fabulous animals, then 
the great scenes that enable us to construct ideas of their life, cus- 
toms, and religion, both from the nature of the forms and from the 
inscriptions and the scenes which they portray. In a word, here 
we find the utilization of ceramic decoration carried to the limit of 
perfection. 
Etruscan pottery offers examples quite as remarkable. Then there 
are the celebrated Roman potteries, about which certain archeolo- 
gists have advanced the most unlikely hypotheses to explain the 
famous red luster which covers them. It is to chemistry that they 
should have turned to find the solution of the problem, for it is chem- 
istry that has revealed to us the fact that this luster is a true enamel 
which the Roman potters made by mixing a strongly ferruginous 
clay of rock with a glass composed of sand and carbonate of soda 
with small quantities of alumina and lime. 
This red enamel of the Romans is therefore derived directly from 
the “engobe.” It was applied to the unbaked piece and was conse- 
quently baked at the same time as the clay base itself, the tempera- 
ture being comparatively low, about 900°. 
It is pretended that we do not know how to duplicate this beautiful 
red; nothing, however, could be more incorrect. We have a rock, the 
sandstone of Thiviers (Dordogne), which, when mixed with a glass, 
or, more correctly speaking, a frit rich in silica, gives us exactly the 
same enamel that we admire on the Roman pottery. 
In this field we are even more advanced than were our predeces- 
sors, for we can vary at will this red tone from an orange shade all 
the way to brown. All that need be done is to add to the glass (or 
frit) certain elements such as alumina, boric acid, borax, or zinc 
oxide, the proportions of which can be infinitely varied. 
The Romans, however, abandoned ceramic painting to devote 
themselves entirely to sculpture. Their vases ornamented in relief, 
