Early in the present century, a manufactory was also opened at Bow, to make church-yard monuments and architectural details in terra-cotta, by Van Spangen and Powell ; but it was soon closed. Some small works were opened also in various country places, but with little success. A few years prior to the International Exhibition of 1851, an inquiry sprang up for architecthral details and garden ornaments, which caused the production of many exCellent examples for the Exhibition. These came from many places in England, and some from Ireland and Scotland ; nearly every class and variety of terra-cotta then manufactured found a place, and the specimens from France, Germany, Italy, and Switzerland were numerous.
Very little terra-cotta was painted and enamelled in the 18th century, and we are only now beginning to imitate the enamelled terra-cotta of the 14th, 15th, and 16th centuries. Since 1851, the use of terra-cotta has very largely increased in England, and it has now become a staple building-material, besides branching out in innumerable directions for ornamental and useful purposes. Considerable quantities of English terra-cotta have been exported during the past 25 years to India, Australia, New Zealand, and the United States. Within the past 10 years, the Americans have established several manufactories for this ware.
Red terra-cotta mouldings are now used in combination with red brick-work in all parts of England, and the making of moulded bricks of this class is a special business. Machinery is employed in this work, hut the more ornamental and artistic pieces are pressed into plaster moulds ; so also are buff and white bricks, which are coloured and enamelled for string courses and dados. White, buff, brown, red, and other clays of various tones are now used for ornamental works, and for busts, statuettes, relievi, 0,nd architectural details. Tlae painting, gilding and enamelling of terra cotta is rapidly improving, and thus employment of a highly artistic character is afforded to women. Busts and statuettes are to be seen in the Royal Academy Exhibitions modelled iu terra-cotta clay, and fine as original works fresh from the touch of the sculptor, without the process of moulding. Architects and sculptors are paying much attention to this subject of original modelling in terra-cotta, and we may hope very soon to rival the works of Lucca della Robbia, Bernard Pallissy, and other old plasters. It may be interesting here to introduce Broguiart's analysis of the clay bodies of the two great modellers just named, before giving a statement of analyses of English clays used in terra cotta, and a list of clays especially fitted for this material. Brogniart gives the following as the
elements of tile wares of:— All these clays will stand fire well, and are much used. In addition, the following are in common use for ornaments1 and moulded work, and for tiles :—Stone-ware, black and red clays, from Wareham ; red and buff clays from near Tamworth, Staffordshire Potteries, Bishops Waltham, N. Shields, Aldrington and Brighton, Leeds, Huntingdon, Arley, Worcester, Tamar ; red clays from Broseley (Shropshire), Ipswich, Penybont, Knutsford (Cheshire), Northwich, Farnham, Maiden head, Bucknell (Berks), Norwich, and Pluckley (Kent). The Cornish, Devon, Dorset, and other clays which burn to a light oolour, as a rule will stand a higher degree of heat than the red clays, and generally shrink lees in the fire. There is great difference in the weight of clays when dried and ground ; in some, as much as 25 per cent. All are improved by weathering, and, after tempering and mixing, by age. Many of the strong red clays become blue under .certsio conditions of burning, and some become readily discoloured. Great care is necessary in firing red ware to maintain a uniformity of tone, and avoid cracking and warping. Red terra-cotta in some cases is improved by combining two or more clays. Black, chocolate, and other dark colours have red clay as the base, to which is added calcined ochre, maoganese, and other substances.
Many clays are very pure, and do not require washing ; some, however, contain pyrites, or other substances whioh necessitate careful washing through sieves, or what is termed " slipping." Coloured bodies for terra-cotta or tiles should be always mixed in the slip state, and brought to a proper consistency for working on a slip-kiln. Many clay bodies are now, after slipping, passed through machines constructed to press out the superfluous water, and leave the clay in a pasty state fit for itnmediate use. Some manufacturers only partially dry the clay, then crush it in a rolling mill, mixing with it gruund potsherds, sand, eze., and then pass the whole through a pug-mill. Others dry the clay thoroughly, and grind it to powder between horizontal stones, mix what they desire with it, and then pug the whole, occasionally pass ing it twice through the pug mill. When different clays are combined in the dry state to make one body, it is im portant this should he done. Clays used for mouldings are often pugged as taken from the pit, and at once trans ferred to a moulder's or machine-worker's charge. It is not safe, however, to make very large pieces by ma chinery.