A better surface is obtained by means of porcelain enamel, which is a thin film of porcelain "fired" on to a fireclay body. The piece of fireclay, modelled to the required shape, is burnt in the kiln in the usual manner without the addition of salt. It is then known as "bisque" or "biscuit" ware, from its porous appearance, and the enamel is applied by covering the surface (generally by dipping) with the liquid slips and glazes necessary to produce the porcelain enamel of the required kind and colour. The article is again fired in a kiln, in order to fuse the materials applied to the surface and convert them into a thin sheet of porcelain, which, if the process has been properly carried on, will be thoroughly adherent to the " biscuit" body. In many cases, however, the enamel is far from satisfactory. It may be cracked in firing, or may be so loosely adherent as to be easily flaked off by a blow or by frost. Enamelled bricks are generally made in this manner, and the enamel of inferior qualities frequently fails by flaking off. In this, as in so many cases, cheapness in first cost is not always true economy. It is better to pay a fair price for a sanitary fitting made by a firm of good reputation than to buy a cheap fitting made no one knows where.

Enamelled ware of this kind is used for sanitary fittings of medium quality and also for very heavy fittings of the best class, such as urinal-stands, large sinks, and baths. In some cases the goods are sorted into two or more qualities, the inferior ware being defective either in shape or in the enamel.

"Whiteware."- With the exception of these heavy fittings, the best sanitary goods are made of some kind of white earthenware or pottery suitably glazed. Different manufacturers use slightly different mixtures of clays, flints, etc, and adopt distinctive names, among which may be mentioned "Queensware," "Titanite," "Vitrina" ware, and "Vitro-porcelain" For convenience they may all be classed together as whiteware or porcelain. It is practically the same material as that used for ordinary household crockery, and, like this, varies in strength, correctness of form, firmness and durability of glaze, and in other respects. The quality of the pottery must be considered in appraising the value of sanitary ware, exactly as in the case of plates and dishes.

The manufacture of a piece of sanitary pottery of this kind is not by any means a simple matter. Failures innumerable have occurred in arriving at the results which are now possible, and the greatest skill and care have still to be exercised in order to produce a perfect piece of work. A brief description of the method of manufacture adopted at Twyfords' Cliffe Vale Works, Hanley, will show what skill and care are required. The selection of the ingredients is the first step in the process. These consist of kaolin or. china clay, blue or ball clay, flints, and Cornish stone. Kaolin is the finest kind of clay, and is prepared from decomposed granitic or felspathic rocks; it contains a certain amount of potassium, and gives fineness of texture and plasticity to the final mixture. Blue or ball clay is a fairly pure hydrated silicate of alumina, and is therefore a true clay. It is of dark grey colour, but burns white, and is introduced to give strength to the mass. Flints are pure silica, and are added to give rigidity and to control contraction. Cornish stone is a partially-decomposed granite, and serves as a flux under the influence of fire.

Each of these ingredients has to be prepared separately. The flints must first be calcined, then crushed, and ground between hard stones in water. The Cornish stone is similarly treated, except that it does not require calcining. The clays are disintegrated and purified by agitation with water. In each case the material must be so finely triturated as to be held in suspension by the water. The four liquids are then mixed together in proper proportions, which vary according to the nature of the earthenware required and according to the amount of solid matter in suspension. To this mixture metallic oxides are added when it is desired to give colour to the body of the ware. Coarse particles are removed from the "slip" by passing it through wire and silk sieves; and fine particles of iron, which would render the earthenware speckled, are extracted by running the slip along a trough in which a number of magnets are placed. A large proportion of the water in the slip is then removed by means of filter-presses, from which the clay is taken to the pug-mill. This is a cylindrical apparatus with revolving steel knives, by which the clay is reduced to uniform consistency, and from which it is forced in a plastic state, ready for the potter.

Before the potter can use the clay he must have full-size plaster models of the various parts of the articles to be made. It is impossible to mould a complicated piece of sanitary ware in one piece. The ware must be built up in pieces, each of which must be separately moulded. The clay is "pressed" firmly into the moulds, so that it will be absolutely homogeneous, and then the operation of "stick-ing-up" is performed, whereby the different pieces are joined together. If this operation is not well done, the joints crack during firing. The "Twycliffe" water-closet basin is composed of no fewer than thirty-two pieces, separately moulded and. then "stuck" together. After partial drying the ware is "fettled" by "trimming the edges with a knife, sponging out all mould marks, and finally finishing with a piece of horn until the surface is perfectly smooth." The ware is then dried at a moderate temperature, and is afterwards dressed by rubbing gently with very fine sandpaper.

It is now ready for the kiln. Great care has to be exercised in placing the articles in the kiln. They are protected by enclosure in earthenware "seggars." The temperature of the kiln and the duration of the firing have also to be carefully regulated. But into this part of the process of manufacture we need not enter.

The ware leaves these kilns in the "bisque" or "biscuit" state, and is then stored in a warehouse and carefully examined. Damaged pieces are thrown out, and pieces containing slight cracks, which can be stopped, are marked and passed on to women who clean the pieces and repair the defects with liquid stopping.

The ware is now ready for printing or decorating, or (if it is to be left plain) for dipping into the liquid glaze. This is prepared from ground flints and other ingredients, and is of such a composition that, on firing at a high temperature, it forms a thin coat of glass on the surface of the pottery. The glaze generally contains a certain amount of lead, and this renders the process of dipping a dangerous one, unless careful precautions are taken and absolute cleanliness observed by the workpeople. After being dipped, the ware is touched up by means of a camel-hair pencil, and the glaze is sponged off those parts which are to be left un-glazed. The ware is then dried at a moderate temperature, and the process of manufacture is completed by burning it again in kilns to fuse and fix the glaze. This operation requires great care both in placing the ware in "seggars" and in regulating the temperature and duration of the firing.

This brief outline of the process of manufacture will serve to show that good sanitary ware is difficult to produce, and is necessarily costly. If a good piece of pottery is required, a good price must be paid for it.

The pottery which has just been described has a more or less porous body protected by a thin coating of glass, but within recent years attempts have been successfully made to produce ware which is practically vitrified throughout, and is therefore non absorbent. This is a valuable improvement, as it sometimes happens that the glaze is not perfect throughout the hidden parts of a complicated piece of pottery, or that, if perfect when it leaves the kiln, it is subsequently damaged. In such cases a porous body is apt to become foul. Non-absorbent ware of this kind is now made by manufacturers of the best sanitary pottery, and sold under various names. It is slightly more expensive than ordinary ware.