For polishing those pieces of watch work which are not to be gilt; after smoothing them with grey or blue-stone and water, they polish them with rot ten-stone well washed over, and conse quently very fine, ground up with olive oil, and finish them with dry rotten-stone.
This rotten-stone is a kind of very light tripoli, but finer and more friable than the other sorts. It is found in Eng land, and is highly esteemed for polish ing ; it is of an ashy-grey tint, and occurs in thin layers, upon the compact carbonate of lime, near Bakewell. The i polishing of steel is not executed in the same manner as in polishing the softer metals ; the steel is not polished until it has been hardened, and the harder it is the more brilliant will be its polish. The substances above indicated for polishing other metals are not powerful enough to attack a substance so hard as this. We most employ emery ground in oil, before used. Hardened steel is either polished flat, like glass, or out into facets, like a diamond; conse quently, the lapidary's mill is used. They commence by smoothing the work with rather coarse emery, then with finer emery, and finish with the finest. The perfected, they polish it with English rouge, tritoxide of iron and oil, and finally finish it with putty of tin (peroxide of tin? and water ; but if upon mills, or laps of zinc, then without the use of water. When the steel articles consist of raised and hollow work, they are smoothed and po lished with the same substance ; but the instruments are, as in the case of less harder metals, pieces of wood, properly shaped, and employed in the same man ner. The finish at Sheffield is effected with the female hand.
Polishing Ivory, Bone, Horn, and Tor toise-shell. Ivory and bone, either plain or ornamented ; and ivory or bone arti cles admit of being turned very smooth, or, when filed, may afterwards be scrap ed, so as to present a good surface. They may be polished by rubbing them first with fine glass paper, and then with a piece of wet linen cloth dipped in pow dered pumice-stone ; this will give a very fine surface, and the final polish may be produced by washed chalk, or fine whiting applied upon another piece of cloth wetted with sosy-suds.
Horn and Tortoise-shell. A very per fect surface is given by scraping them ; the scraper may be made of a razor blade, the edge of which should be rubbed upon an oil-stone, holding the blade near ly upright all the while, so as to ford an edge like that of a currier's knife ; and which, like it, may be sharpened and im proved by burnishing, at least as far as its hardness will permit. To prepare the
properly scraped for polish ing, it is first to be rubbed with a buff, made of woollen cloth, perfectly free from grease. After the work has been made as smooth as possible by this means, it must be followed by another buff or bob, on which washed chalk or dry whiting is rubbed ; the comb, or other article; is to be slightly moistened with vinegar, and the buff and whiting will produce a fine gloss, which may be completed by rubbing it with the palm of the hand, and a small portion of dry whit ing or rotten-stone.
Polishing Iron, Brass, the. A beauti ful surface is produced upon cast-iron, steel, and brass-works, by means of emery sticks, and others coated with crocus. Mix drying linseed-oil, in the proportion of one-eighth part with glue, and coat the surfaces of pieces of soft yellow pine, fir, or deal, without turpentine or knots, which are about eight inches long, and five-eighths of an inch square, and nicely planed. Lay on a coat of thin glue, and when that is dry, another composed of glue mixed with the emery or crocus, and then in stantly sift over the wet surface the emery, or crocus in powder, by means of a sieve. Emery is employed 'of differ ent degrees of fineness, and sticks thus coated with each may be used in suc cession, to smooth the work ; and, lastly, sticks coated with glue and crocus are used to give the finishing polish. Such emery and crocus sticks are very durable, and are equally useful on works in the lathe, as well as upon fiat surfaces ; are superior to the glass or emery papers ordinarily used; and greatly to emery mixed with oil, and applied upon sticks in the common way.
Hindoo Polish. Powdered corundum with melt lac is used to polish all stones, first sprinkling them with water.
German Polish. The wood is pre pared with pumice-stone rubbed fiat, oiled, and then rubbed together till smooth. The only varnish then need is a solution of seed-lac or shell-lac in alcohol, the clearest grains of lac being for the lightest varnish. It is colored red with Brazil wood, and yellow by tur meric root. It is applied with a rubber of five pieces of linen ; the varnish is laid on with a sponge, and when soaked, linseed-oil is added, and the whole gone over with a rubber.