TIN SCTa(JJed, or scoured with iron- scales, then pulverized sal-ammo- niac is strewed over it, and the melted tin is rubbed oft the surface with a solid piece of sal-ammoniac. The process for covering iron ves- sels with tin, corresponds with that last described ; but they ought to be previously cleaned with the mu- riatic acid, instead of being scraped or scoured. In 1785, a patent was granted to Mr. John Poulain, for his tlew coniposition in the process of tin- ning culinary and other vessels. He dire£bs lib. of pure, or grain- tin ; if oz. of good malleable iron ; 1 dr. of platina ; 1 dwt. of silver ; and 3 gr. of gold ; to be fused in a crucible, with 1 lb. of borax, and 2 oz. of pulverized glass ; after which the mixture is to be cast into small ingots. To ^dapt such composi- tion to the intended purpose, the patentee states, that it must be put into a metal mortar, placed over a charcoal fire, and pounded with a heated metal .pestle ; after which it should again be plaCed over the fire, in an iron mould, where the compound ought to be stirred, and .suffered to cool. The vessel is then to be covered with tin and sal-ammomac> as is usually prac- tised^ the part thus tinned must be well cleaned, and a coat of the composition above described be laid on with sai-ammoniac, in an lloiform manner; next, the uten- sil ought to bt gradually heated, that every part may be annealed ; when it should be immersed in Cold water, and the rough particles scraped, or rubbed off, and scoured with sand. — Mr. Poulain's in- vention is ingenious, though too expensive, to be generally adopted : wc therefore subjoin the following process, by which tlie vessels not mo. XIV.-— 'VOL. IV.
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only acquire additional strength,' but are also secured against the ac- tion of acids, for a longer period than is effeiSted by the common methods of tinning t Let the uten- sil be cleaned in the usual manner j its inner surface be beaten on a rough anvil, that the tinning may more closely adhere to the copper; and let one coat of pure tin be laid on with sal-ammoniac, as above dire£ted in the process for tinning old copper. A second coat, con- sisting of two parts of tin, and tk7-ee of zinc, must next be uni- formly applied with sal-ammoniac, in a similar manner : the surface is now to be beaten 5 scoured with chalk and water; smoothened with a propei" hammer ; exposed to a moderate heat; and, lastly, dipped in melted tin; by whick means both sides will be tinned at the same time. — Such tinning is stated to be very durable, and to have a permanent beautiful co- lour, so that it may be advanta- geously used for various metal utensils and instraments, which may thus be efFe6tually prevented^ from RUST. Lastly, as many families living a:t a distance from towns, either have no opportunity of sending their copper utensils to be re-tinned ; or carelessly overlook such necessary repair, we think it useful to ob- serve, that the whole process may be easily performed by servants, who possess common skill and dex- terity. For this purpose, the ves- sel ought to be previously scoured, and dried; then exposed to a mo- derate heat, with such a portion of pure grain-tin as may be sufiicient to cover the inner surface : when this metal is melted, a small quan- tity of sal-ammoniac should be strewed over it j and, immediately •Q after.
