und bearing
representations of the digging of clay for pottery.

[FIG. 15.--Shapes of Greek Vases.]

The improved manipulation of the clays, and the increasing knowledge
that the colour of a clay could be modified by admixture of other
substances such as ruddle and ochre, really paved the way for what is
known as the glaze of the Greek painted vases. This delicate gloss, so
thin as to defy analysis, has been commonly called glaze, but it
cannot be a glaze in the sense of a separate coating of finely-ground
glass superimposed upon the clay. In all probability, as the Greek
potter used finer and finer clays and so was enabled to perfect his
shapes, he found that after a vase had been "thrown" he could get a
closer texture on it by dipping it in a slip of still finer clay
material and then smoothing it down and polishing it on the wheel when
sufficiently dry. But the mixtures he would use for such a purpose--of
very siliceous clay and ochre--would, when they were burnt in the
Greek kiln, not only fire to a beautifully bright colour, but also to
a glossy surface, especially where the flames had freely played about
them; and it is more in accordance with our knowledge to believe that
the exquisitely thin gloss of the finest Greek red vases was produced
in this way, for it seems impossible that it can have been a coating
of any special glaze.

In any case we may state broadly that the body of Greek vases is
always fine in grain, fired hard enough to give forth a dull metallic
sound when it is struck, but seldom fired above a temperature of about
900 Deg. C., which a modern potter would consider very low. When broken
the inside is generally found to be duller in colour, and is often
yellow or grey, even where the external surface is red. The material
is exceedingly porous, and allows water to ooze through it (another
proof that it was not glazed). Numerous analyses of the material of
Greek vases have been published, but they tell us nothing of the
secrets of the Greek potter. The results of a great number of these
analyses may be summed up as follows: silica, 52-60 parts; alumina,
13-19 parts; lime, 5-10 parts; magnesia, 1-3 parts; oxide of iron,
12-19 parts. Analyses of a thousand ordinary simple red burning clays
would give a similar result. It is to the glory of the Greek potter
that with such ordinary materials, by the exercise of selection,
patie