Inventions in the Century

by William Henry Doolittle

From the early dawn of human history to its present noonday civilisation the progress of man may be traced in his pottery. Before printing was an art, he inscribed on it his literature. Poets and painters have adorned it; and in its manufacture have been embodied through all ages the choicest discoveries of the chemist, the inventor and the mechanic.

It would be pleasant to trace the history of pottery from at least the time of Homer, who draws a metaphor from the potter seated before his wheel and twirling it with both hands, as he shapes the plastic clay upon it; to dwell upon the clay tablets and many-coloured vases, covered with Egyptian scenes and history; to re-excite wonder over the arts of China, in her porcelain, the production of its delicacy and bright colours wrapped in such mystery, and stagnant for so many ages, but revived and rejuvenated in Japan; to recall to mind the styles and composition of the Phœnician vases with mythological legends burned immortally therein; the splendid work of the Greek potteries; to lift the Samian enwreathed bowl, “filled with Samian wine”; to look upon the Roman pottery, statues and statuettes of Rome’s earlier and better days; the celebrated Faience (enamelled pottery) at its home in Faenza, Italy, and from the hands of its master, Luca della Robia; to trace the history of the rare Italian majolica; to tread with light steps the bright tiles of the Saracens; to rehearse the story of Bernard Palissy, the father of the beautiful French enamelled ware; to bring to view the splendid old ware of Nuremberg, the raised white figures on the deep blue plaques of Florence, the honest Delft ware of Holland; and finally to relate the revolution in the production of pottery throughout all Europe caused by the discoveries and inventions of Wedgwood of England in the eighteenth century. All this would be interesting, but we must hasten on to the equally splendid and more practical works of the busy nineteenth century, in which many toilsome methods of the past have been superseded by labour-saving contrivances.

The application of machinery to the manufacture of brick began to receive attention during the latter part of the eighteenth century, after Watt had harnessed steam, and a few patents were issued in England and America at that time for such machinery of that character, but little was practically done.

The operations in brickmaking, to the accomplishment of which by machines the inventors of the nineteenth century have devoted great talent, relate:

First, to the preparation of the clay.—In ancient Egypt, in places where water abounded, it appears that the clay was lifted from the bottoms of ponds and lakes on the end of poles, was formed into bricks, then sun-dried, modernly called adobes. The clay for making these required a stiffening material. For this straw was used, mixed with the clay; and stubble was also used in the different courses. Hence the old metaphor of worthlessness of “bricks without straw,” but of course in burning, and in modern processes of pressing unburnt bricks, straw is no longer used. Sand should abound in the clay in a certain proportion, or be mixed therewith, otherwise the clay, whether burned or unburned, will crumble. Stones, gravel and sticks must be removed, otherwise the contraction of the clay and expansion of the stones on burning, produce a weak and crumbling structure.

Brick clay generally is coloured by the oxide of iron, and in proportion as this abounds the burned brick is of a lighter or a deeper red. It may be desired to add colouring matter or mix different forms of clay, or add sand or other ingredients. Clay treated by hand was for ages kneaded as dough is kneaded, by the hand or feet, and the clay was often long subjected, sometimes for years, to exposure to the air, frost and sun to disintegrate and ripen it. As the clay must be first disintegrated, ground or pulverised, as grain is first ground to flour to make and mould the bread, so the use of a grinding mill was long ago suggested. The first machine used to do all this work goes by the humble name of pug mill.

Many ages ago the Chilians of South America hung two ponderous solid wood or stone wheels on an axis turned by a vertical shaft and operated by animal power; the wheels were made to run round on a deep basin in which ores, or stones, or grain were placed to be crushed. This Chilian mill, in principle, was adopted a century or so ago in Europe to the grinding of clay. The pug mill has assumed many different forms in this age; and separate preliminary mills, consisting of rollers of different forms for grinding, alone are often used before the mixing operation. In one modern form the pug mill consists of an inverted conical-shaped cylinder provided with a set of interior revolving blades arranged horizontally, and below this a spiral arrangement of blades on a vertical axis, by which the clay is thoroughly cut up and crushed against the surrounding walls of the mill, in the meantime softened with water or steam if desired, and mixed with sand if necessary, and when thus ground and tempered is finally pressed down through the lower opening of the cylinder and directly into suitable brick moulds beneath.

Second.—The next operation is for moulding and pressing the brick. To take the place of that ancient and still used mode of filling a mould of a certain size by the hands with a lump of soft clay, scraping off the surplus, and then dumping the mould upon a drying floor, a great variety of machines have been invented.

In some the pug mill is arranged horizontally to feed out the clay in the form of a long horizontal slab, which is cut up into proper lengths to form the bricks. Some machines are in the form of a large horizontal revolving wheel, having the moulds arranged in its top face, each mould charged with clay as the wheel presents it under the discharging spout of the grinding mill, and then the clay is pressed by pistons or plungers worked by a rocking beam, and adapted to descend and fit into the mould at stated intervals; or the moulds, carried in a circular direction, may have movable bottom plates, which may be pressed upwards successively by pistons attached to them and raised by inclines on which they travel, forcing the clay against a large circular top plate, and in the last part of the movement carrying the pressed brick through an aperture to the top of the plate, where it is met by and carried away on an endless apron.

In some machines two great wheels mesh together, one carrying the moulds in its face, and the other the presser plate plungers, working in the former, the bricks being finally forced out on to a moving belt by the action of cam followers, or by other means.