Enamels and glazes, properly speaking, are opaque, vitreous, coloured materials, tractable in the fire, and used in ornamenting metals and pottery; but it will be convenient to add here a few recipes for so - called "enamels" on other substances.

Cloth

As a substitute for leather, enamelled cloth is now largely used where lightness and pliability are desirable. Having the appearance of leather, and nearly, if not quite, its durability, it is used where strength is not so important as a good appearance. In the covering of carriage tops, the upholstering of furniture, the covering of trunks and travelling bags, a great quantity is used, and it is also employed in garments, coverings, etc, as a protection from water. The details of its manufacture are very simple.

The foundation of the article is cotton cloth of the best quality, and generally made expressly for this purpose. The cloth is taken from a bale and wound upon a large cylinder preparatory to receiving its first coat. It is then passed between heavy iron rollers, from the top one of which it receives its first coating of composition. In many places the covering is spread by a knife under which the web passes, The composition is made of linseed - oil, lampblack, rosin, and a few other ingredients, which are boiled together till they reach the con - sistency of melted tar. From between the cylinders it is carried to a drying frame made in the shape of a reel, and subjected to a high temperature in the drying - room, which is heated generally by steam pipes. After the drying process it is given to workmen, who make all the rough places smooth by rubbing with lump pumice and water. The cloth is then passed through the same operations as before, rolling, drying, and rubbing, and this is repeated 3 to 5 times, or until the required thickness has been laid on. After the last scrubbing down, the fabric is taken to another department, thoroughly varnished, and again passed through the heater. It now appears as a piece of cotton cloth, with one black side looking very much like patent leather.

One step yet remains to be taken. The cloth is passed between heavy rollers, which cover its surface with regular indentations resembling the grain of leather. It is now ready for the market. As many frauds are perpetrated in this article as in any other. Manufacturers who desire to turn out a heavy material, first fill the cloth with clay, and the result is an enamel that will crack during the cold weather of winter; or, in their endeavour to produce a cloth that will stand a low temperature without cracking, they make material that will be sticky in summer. The poor quality is used in the cheap trunk and bag trade, but none but the best will do for the outside wear that comes upon carriage tops. {Manufacturers' Gazette.)

Dr. Ballard has some valuable remarks on this manufacture in one of his reports. The japan or enamel used for enamelling cloth or leather is usually prepared, he says, by boiling Prussian blue or peroxide of iron in raw linseed - oil. At the Leather Cloth Co/s works at Stratford, the pots for making it, 16 in number, each holding 150 gal., are set in brickwork and arranged along 2 sides of a building devoted to the purpose. The pots are enclosed in brickwork chambers having sliding iron shutters in front, which can be drawn down during the boiling. The fumes escape by pipes, and are drawn away by a fan, and delivered into the ashpit of the boiler of the works, for consumption, thus preventing nuisance. The pots are fired from the rear, and the enamel is allowed to cool before being ladled out.

The manufacture of leather cloth (American cloth) and of table covers is carried on at some places on a very large scale in extensive factories, and at others in much smaller establishments. The details of the operation may differ in different works, correspondingly with differences in the precise article manufactured and the use to which it is to be applied; but the essential features of the business are the same in all works. The enamelling of leather and pasteboard for the preparation of what is called "patent leather" and the peaks of military and other caps is a very similar process, "but is conducted only in small establishments.

The enamel used at the smaller establishments is ordinarily purchased from persons who prepare it; but at the larger establishments it is usually made on the premises. Briefly, the process consists in laying on the varnish or enamel smoothly upon the cloth, etc, and then exposing the varnished material to a high temperature in an oven or heated chamber.

For the making of table - covers, the cloth is usually manipulated in convenient lengths, and the same is mostly the case when leather cloth is made in the smaller establishments for the covering of boxes and cabs. In the large establishments for the manufacture of leather - cloth, the cloth is made in rolls of many yd. in length. In some cases, the cloth undergoes preparation before the varnish is laid on, with the object of preventing imbibition, and sometimes to impart thickness and substance to the article made. This preparation consista either in sizing the surface, and perhaps after sizing putting on a layer of paint, or in laying on at once a paste made with boiled linseed - oil, whiting, and water. When the surface thus prepared is dry, the varnish is laid on. When a long roll of cloth has to be varnished, the varnish is spread on by means of a machine adapted to the purpose, which puts it on smoothly and evenly as the cloth passes through it, and as the cloth leaves the machine it goes on directly to the drying chamber.

When the cloth is varnished in lengths, it is laid upon a long smooth table, and a workman lays the varnish on evenly by hand, using for the purpose a flat instrument or scraper.. After being varnished, it is hung up in a drying - room, the capacity of which varies of course with the size of the works. The larger establishments have several such rooms, a considerable extent of the buildings being thus occupied. The room is heated to about 170° F. (77° C.) by means of steam pipes or hot - air pipes, or by means of heated air driven in by a fan, and is ventilated by means of windows the sashes of which can be opened, or by means of an unpointed tiling to the roof. Much vapour strongly impregnated with acrolein is given off and fills the chamber, rendering the atmosphere very irritating to nose, eyes, and respiratory organs. Some of the vapour condenses as a brown liquid on the walls and panes of the windows. It is a common practice to keep the windows closed at night, and to open them in the mornings for the thorough ventilation of the room. In small establishments, instead of a lighted room, a small but sufficiently capacious dark chamber, more of the nature of an oven, heated in the same way or by hot - water pipes, is in use.