celain_.--This beautiful and somewhat mysterious ware--often
called "Gombroon" ware--apparently made its appearance in the 13th
century, though the bulk of the known examples are not earlier than the
17th or 18th century. The ware is quite translucent and is of soft and
delicate texture. Unlike Chinese porcelain, it was made from a mixture
of pipe-clay and glass, and was glazed with a soft lead glaze; so that a
fragment of it would melt to an opaque glass in an ordinary porcelain
oven. It is principally met with in the form of dishes, bowls (often
mounted on feet) and saucers. The pieces are generally very thin and are
either perfectly plain or bear flutings or simple wavy patterns incised
in the paste. Most characteristic and beautiful is the decoration by
means of delicate perforations either straight or lozenge-shaped. In the
finest pieces the perforations are filled with glaze, and then they form
a decoration analogous to the well-known "rice-grain" decoration of the
Chinese. Occasional pieces are found decorated with colour, either a
delicate green, producing an effect like pale bright celadon, or the
well-known Persian blue ground; and this is sometimes decorated with
lustre patterns. Nowhere can this rare and delicately beautiful ware be
so well studied as in the Victoria and Albert Museum.

_Lustred Ware_.--The decoration of pottery with iridescent metallic
films is one of the most astonishing and beautiful inventions ever made
by the potter. Hitherto we have seen only coloured clays, coloured
glazes, or colours fired under the glaze, but we are now brought face to
face with a colour effect produced by refiring the finished glazed
pieces, at a lower temperature, with pigments painted upon the glaze
(fig. 40; see also Plate V. 13th-century Persian lustre). How such a
practice originated is probably an idle speculation, but it may have
come through repeated attempts to decorate pottery with gold. If gold
was painted under the glazes of these ancient vases, it would probably
vanish and leave no trace; but gold, alloyed with much silver, applied
over the finished glaze and refired, in the attempt to make it adhere,
may have given the first films of iridescent colour. We know certainly
that before the 13th century the elements of the process had been
mastered, and that the potters of the nearer East had learnt that by
mixing some compound of silver (doubtless the sulphide) with clay, and
painting the mixture on the fi