THE MANUFACTURE OF ENAMELED THE art of enameling brick is older than recorded history. It was practiced in Assyria, Babylonia and Chaldea. The Moors brought the art with them from the East when they ex tended their domain into Spain and over Western Europe. The Moors derived their knowledge from India, and primarily from China. With the decline of the Moorish civilization the art of manufacturing enamel brick and tiles was lost to the Western world, still being retained, however, in the Orient.
The great surviving monument of Moorish art in brick and tile enameling is the interior decorations of the walls of the Alhambra Palace at Granada, in Spain. For over a thousand years knowledge of the art of brick and tile enameling slum bered in Europe, and was only revived when the Crusaders from France visited Byzantium, Palestine and Syria, and when returning carried to France knowledge of enamels and also workmen skilled in their application to clay bodies. From France — especially from Normandy — the art of making enameled brick and tiles spread through continental Europe and to England.
With the vanishing civilization of mediaeval times this art was again lost to Europe. It has only been during the past forty years that the manufacture of enameled brick has again been put upon a successful basis in England, and only during the past twenty years that it can be said to have become financially profitable.
The problem which now confronts us is " Why can we not manufacture enameled brick which will compete with those of England in both quality and price?" There is only one answer to this question—we lack specific knowledge regarding the details of the subject.
Diodorus Siculus relates that the brick of the walls of Baby lon, erected under the orders of Semiramis, were decorated with all kinds of living creatures portrayed in various colors upon the brick before they were burned.
In spite of this positive information concerning the way in which the enamel decorations were applied to the brick which formed the facings of the walls of Babylon, nearly all persons who, forty years ago, endeavored to manufacture enamel brick, thought that it was necessary to enamel the brick only after they had been once burned. The loss of time, the injuries
which resulted to the brick, and the great cost incurred in first burning the brick, then enameling them, and then burning the brick the second time, forced the manufacturers of this class of goods to abandon such wasteful methods, and to apply the en amel to the brick in the green state and complete the burning process in one operation. A brick which has once been burned and afterwards enameled and again burned does not make as good a product as is had by the one-burning process, as the enamel being applied to the dry surfaces does not adhere firmly, and commonly scales completely off after the brick are laid in the wall. The enameling as well as the burning of the brick must, however, all be done in one firing, and if done otherwise the results will be neither satisfactory nor profitable.
It will readily be seen from the foregoing remarks that easily fused enamels, such as those containing lead, cannot be em ployed, as such enamels would be destroyed in the heat of the kihi and pass out with the gases long before the brick them selves were burned, especially as the brick used for enameling are made from fire-clay.
Hence it is of primary importance for enamel to coincide with the contraction and expansion of the clay body to which it is applied. It is also necessary that enamels should not be fusible at any special temperature, as the fusing point of en amels must vary according to the degree of heat which the clay body upon which they are placed will stand. The constituents, therefore, which form the enamel must be of such a character that their mixture will withstand high temperatures without danger or injury, and the brick to which the enamel is applied must be sufficiently refractory so as not to melt or get out of shape during the time when the enamel is being attached to it in the firing process.