Under this heading are placed those glazed terra-cotta products which are used for architectural ornamentation, and which are distinguished by their shape from enamelled bricks.

The birthplace of this style of decoration, as of many other arts, was the East. The Assyrians and the Persians, probably also the Chinese, were the first peoples who applied enamelled products to the ornamentation of buildings. The Egyptians used glazes for their vases, but do not appear to have used them in their edifices.

After having disappeared, under the Greeks and Romans, for several hundred years, this style of decoration was again in favour during the 10th century in the East, and afterwards in Europe from the 12th century until the 16th, when it once more fell into comparative neglect. These ornaments regained their popularity in the 19th century in certain countries, for instance in Switzerland, Germany, England.

In France, there is also a movement in their favour, but of a more tentative nature.

Speaking generally, all potteries can be enamelled; all that is required is that the paste and glaze should harmonise, so that crazing may be avoided.

The composition of the glazes depends upon the nature of the clay.

The latter may have the composition of faience, of stoneware, or of porcelain; hence the products are of three classes.

1. Porcelains

Several attempts have been made to introduce porcelain into the facings of walls. MM. Parvillee, the skilful ceramists, had exhibited in 1889 some very interesting specimens of decoration executed on a special porcelain, the same product which they have successfully applied to the manufacture of porcelain articles for electrical purposes. The cost of the primary materials and certain difficulties in the manufacture have probably prevented them from continuing their experiments, and this is much to be regretted.

We know that porcelain is extensively used in the far East for the decoration of both the inside and outside of walls.