the covering or lining of any thing with melted tin, or with tin reduced to a very fine leaf. Looking-glasses are foliated or tinned with thin plates of beaten tin, by a process described under the title Fo-

LIATING; Encycl.

Kettles, Kettles, sauce-pans, and other kitchen utensils, which are usually made of copper, are tinned by the following process: The surface to be tinned, if of new copper, should first be cleaned or scoured with salt and sulphuric acid (vitriolic acid) diluted with water. This, however, is not always done; some workmen contenting themselves with scouring it with sand perfectly dry, or with scales of iron. Powdered rosin is then strewed over it; and when the vessel or utensil is considerably heated, melted tin is poured into it, and rubbed with flax coiled hard over the surface to be coated. This tin may be either pure, such as that known by the name of grain-tin; or a composition consisting of two parts of tin and one of lead. For very obvious reasons, we should certainly prefer the pure tin; but the generality of workmen give the preference to the composition, because the surface coated with it appears more brilliant. The tin is not always put into the vessel in a liquid state; for some workmen strew it in small pieces over the surface to be coated, and then heat the vessel till the tin melts, when they rub it as formerly.

In tinning old vessels which have been tinned before, the process is somewhat different. In these cases, the surface is first scraped with an instrument proper for the purpose, or scoured with the scales of iron, which may be always found in a blacksmith's shop: it is then strewed over with sal ammoniac in powder, instead of rosin, or an infusion of sal ammoniac in stale urine is boiled in it till the urine is evaporated, and it is then tinned with pure tin; the composition of tin and lead being in this case never used. The tin, while liquid, is rubbed into the surface with a piece of sal ammoniac, instead of a bundle of flax. When iron vessels are to be tinned, they are first cleaned with muriatic acid, after which the process is the same as in the tinning of old copper.

In the year 1785, Mr John Poulain of Mortlake, Surrey, obtained a patent for the discovery of a new composition for tinning vessels, especially such as are used for culinary purposes. This composition consists of grain tin one pound, good malleable iron one ounce and a half, platinum one drachm, silver one pennyweight, gold three grains: the whole must be well fused together in a crucible, with one ounce of pounded borax, and two ounces of pounded glass, and then cast in small ingots. The composition, to be fit for use, must be heated and put in a metal mortar, also heated over a fire, and well pounded with a heated metal pestle; when it is well pounded, make an ingot of it, by putting it on the fire in a mould made of iron plate, in which mould the composition must be well stirred and let to cool; then it is fit for use. To apply the composition, first tin the utensil or vessel with grain-tin and sal ammoniac, as is usually done in the common way of tinning; clean well the tinned part of the metal utensil or vessel, and then apply a coat of the composition with sal ammoniac, as is usually done in the common way of tinning; and when the composition is well spread, let it cool; then make it a little red-hot in all its parts, to seal it, and plunge the metal utensil or vessel, while yet hot, in cold water; then, with a sharp scraper, scrape and rub off the rough or grumous particles of the composition applied on the metal utensil or vessel, and scour it well with sand. The same operation must be repeated for every coat of the composition that is applied; two coats of the composition are quite sufficient for culinary utensils or vessels, and a thin coat of grain-tin may be applied over the last coat of the composition, to smooth it. The author adds, that his composition may be employed for covering or plating the surfaces of all materials made of copper, brass, iron, and other metals or mixtures of metals, and that it should be applied with a charcoal fire in preference to any other fire. All this may be true, and it may be a very valuable coating to copper; but the scarcity, high price, and infusibility of platinum, must forever prevent it from coming into very general use.—We think that even the enamelling of vessels for the kitchen must be more common. See that article in this Supplement.

The following process is less expensive, whilst the coating given by it is exceedingly durable, adds strength to the copper vessel, and secures it much longer than the common tinning from the action of acids:

When the vessel has been prepared and cleaned in the usual manner, it must be roughened on the inside by being beat on a rough anvil, in order that the tinning may hold better, and be more intimately connected with the copper. The process of tinning must then be begun with perfectly pure grained tin, having an addition of sal ammoniac instead of the common colophonium or resin. Over this tinning, which must cover the copper in an even and uniform manner throughout, a second harder coat must be applied, as the first forms only a kind of medium for connecting the second with the copper. For this second tinning you employ pure grained tin mixed with zinc in the proportion of two to three, which must be applied also with sal ammoniac smooth and even, so that the lower stratum may be entirely covered with it. This coating, which, by the addition of the zinc, becomes pretty hard and solid, is then to be hammered with a smoothing hammer, after it has been properly rubbed and scoured with chalk and water; by which means it becomes more solid, and acquires a smooth compact surface.

Vessels and utensils may be tinned in this manner on both sides. In this case, after being exposed to a sufficient heat, they must be dipped in the fluid tin, by which means both sides will be tinned at the same time.

As this tinning is exceedingly durable, and has a beautiful colour, which it always retains, it may be employed for various kinds of metal instruments and vessels which it may be necessary to secure from rust.