Gestoso resolves the question sufficiently for our purpose by showing that the term azulejo is usually applied to square tiles of a largish size, the length of whose sides varies between eleven centimetres and eighteen centimetres, aliceres being properly the smaller strips or pieces (technically known as cintas or verduguillos) used in a bordering or frieze. Other decorative pieces of small dimensions, invented in the fifteenth century, were called olambres or olambrillas, and served to lend variety to the red or yellow brickwork of a pavement or a floor.

The production of azulejos in Spain may thus be traced to as far back as the twelfth century. By far the most important centre of the craft was Seville. Here, from the twelfth until the fourteenth century, was made the glazed and decorative tiling which consisted of small pieces of monochrome earthenware—black, white, green, blue, or yellow—cut one by one, and pieced together in the manner of a true mosaic. This process, says Gestoso, was lengthy, difficult, and dear. In the fourteenth and fifteenth centuries the same mosaic would often take the form of a series of narrow, white, ribbon-like strips, with coloured interspaces. Specimens of this “ribbon-work tiling” exist to-day in the Patio de Las Doncellas of the Alcázar (Plate [lii].). Towards the sixteenth century the Sevillano potters discovered a simpler way of making effective and artistic azulejos, which they called the cuerda seca process. This novel method consisted in pressing a wood or metal mould upon the unbaked tile, in such a manner that the outline of the pattern remained in slight relief. This outline was next brushed over with a mixture of manganese and grease, which turns, in baking, very nearly black. The body of the pattern was then filled in with the various colours, which the greasy line completely separated, and thus prepared, the tile was rendered permanent by firing.

LII
MOSAIC OF THE PATIO DE LAS DONCELLAS
(Alcázar of Seville)

This process, in which the patterns are nearly always geometrical, remained in general use until about the year 1550, when it began to be superseded by two others, known respectively as the processes of “cuenca” and “Pisano”.

The cuenca tile was simple and of excellent effect. The pattern, stamped from a metal mould, remained in bas-relief,—a characteristic which caused these objects to be also known as azulejos “de relieve”. The shelving border of each hollow stamped into the tile thus formed a kind of natural barrier which kept the colour there deposited from mingling with its neighbours. When of a larger size, and joined in pairs to form between each two a single motive (ladrillo por tabla), these azulejos were often employed for decorating roofs and ceilings.

The tiles which bear the name of their inventor, Francesco Niculoso Pisano the Italian, who lived and worked for many years at Seville, date from about the same time as the “cuenca” azulejos. In the case of the Pisano tile, there is no indentation caused by the imprint of a mould, the surface being merely coated with a monochrome glaze, painted upon and fired, the decoration thus remaining flat all over. Commonly the ground is white or yellow, with the colour of the pattern shaded blue, or black, or deepish purple. This process, which lent itself to most elaborate and effective schemes of ornament, remained in vogue until the eighteenth century, and was practised, not only by Pisano himself, but by a long succession of his pupils, followers, and imitators.