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total time. The palest work of all is | portions in English weights. Warm the last drawn, and the plate is plunged into water, dissolve the chlorate of potash in the bath for an eighth of the total time. it, then add the acid. Sketch the subject Thus the plate will have had the darkest with some pale but decided water colour, lines in acid the whole time required, the red or yellow for example, using the darker lines half the time, the pale lines point of a small camel-hair brush. This a quarter, and the palest lines one-eighth will remain visible whilst the plate is of the times, as each biting-in has the being etched, which must be done whilst advantage of those which preceded it. it is in the bath; the acid will, of Finish with the dry point where required. course, attack the needle, but this action
HAMERTON'S POSITIVE PROCESS.-By keeps the needles sharp, and they are not this process the work is distinctly seen costly tools. The bath should be formed during operation; black on a white or in an oblong square piece of light wood, silvered ground, without any deceptive about 14 inch thick, and larger than glitter, and exactly as it is to be seen in the well, which must be a square hole, the print. Clean the copper plate, and a little larger than the plate, and rub it with a clean rag and a little of about an inch deep. Cover the board Levi's crême d'argent, cyanide of silver. and well with about six coats of japan, Remove the superfluous cream with a which protects the wood from the action clean rag, and the plate will be properly of the acid, and the dark colour makes silvered." If the cream is too thick, add the plate look whiter from the contrast, a little spirits of wine. If it is wished A thin piece of wood, stained black, must to make the silver of a dead white, be used as a hand-rest. Before using a slightly roughen the surface of the copper new bath or well dissolve a small piece before silvering with fine emery paper, each of copper and of zinc in it with rubbed from right to left, or from left to acid. Lay the plate in the desired posiright, of the way it is intended to work tion, and fix it by pressing small pieces the plate. Use a white ground, made by of modelling wax at the corners against dissolving white wax in ether—a satu- the plate and the board. Etch with an rated solution. Let it settle a few days; ordinary strong sewing needle inserted the clear part only is required, the milky in a holder. It must be sharp enough to portion at the bottom, being undissolved scratch well through the silver, otherwise particles, are probably insoluble and use the line will not blacken at once. The less. To apply this ground, hold the plate wax ground permits the lines to enlarge underneath with a pneumatic holder; pour slowly; thus there is a constant gradathe solution on the silvered side; move tion in thickness from the first to the the plate gently but firmly from side to last lines; as the time of exposure side, so that the solution may run to and diminishes, this property must be carefro, then pour all the superfluous ground fully attended to. Thus, if the subject back into the bottle. In finishing, move requires only about 2 hours' work in the plate more rapidly. Let the ground etching, this must be spread over 5 dry for 3 days. Apply a second coat hours' exposure in the bath, which is the in the same manner, and let it dry for time necessary to produce the darkest 4 days in a quiet room, where it will lines; other work can be carried on pot catch any dust. If the plate is dried simultaneously, but this process cannot by the heat of a spirit lamp, the ground be hurried. if, however, the subject is will be transparent, but not of the dead elaborate, and requires more etching white colour which is desirable. Paint than can be finished in 5 hours, select the back and edges of the plate with for the first sitting various parts over japan varnish to protect them in the the whole plate; clean and re-ground the bath, which must be composed as fole plate; at the second sitting add work to lows ;-Chlorate of potash, 20 grammes; that previously done, and so on until the purs hydrochloric acid, 100 grammes ; plate is finished, so arranging the times water, 880 grammes ; or the same pro- l as to work always at the same period of
dry for 3 days. App let it dry for time necessary Cole can be carried on the operation on unes intended to be of 1 with a delicate gradation. The more perthe same depth. This process is acquired pendicular the needle is held the less burr with a little practice. If necessary to there will be raised; by inclining the efface, it may be done in the usual hand to the right the burr will be inmanner with scraper and charcoal ; creased, if the pressure on the tool realways re-silver before retouching, if mains the same. Practice enables an retouching is required. For cleaning etcher to regulate the pressure on the the plates turpentine is usually em tool ; but if the pressure used has raised ployed, but schist-oil or petroleum are | too strong a burr, it can be partially or better cleansers, and remove the japan entirely removed by using a sharp scraper varnish very rapidly, whereas turpentine worked at right angles to the line. If it dissolves it slowly.
is desired to see the progress of the work ETCHING FROM NATURE.Etching is rub a mixture of tallow and lampblack the only kind of engraving which can over the plate; remove what is superconveniently be done directly from nature. Auous with a soft rag; the effect of the The choice of subjects is the most im- etching can then be fairly judged of. Dry portant point, as, although etching is point etching can now be made to give a admirably adapted for trees and vegeta | large number of impressions, by having tion in all its forms, and for picturesque the plate protected with a coating of buildings and animals, it is not so well steel applied by galvanism. To efface suited for the representation of figures, | faulty work use sand-papers of several or for other subjects, which require deli degrees of coarseness; the coarsest first, cate gradations of tones. For anything then the scraper; finally, rub over with that can be expressed by lines, etching is willow charcoal and olive oil. This leaves very successful, but it is not easy of the plate fit to be etched upon ; if, howapplication to tones. In working from ever, it should be hollowed out by this nature, the shading, in addition to giving process, mark the spot on the back of the the light and dark tints, should also be plate by means of callipers. Lay the face used to indicate the form and texture of of the plate on a block of polished steel, the surface, the lines being drawn in a and give it two or three blows on the direction to indicate form as well as back with a rounded hammer. The entint. Several plates, ready grounded, gravers' copper planers will do this work may be carried in a small grooved box with more precision and skill than can to keep them apart; if only one plate easily be acquired by ordinary etchers. is intended to be used, it can be carried A passage that has been over-bitten may between :wo light boards, but must not be easily reduced by being rubbed with be allowed to touch them. This can be willow charcoal and olive oil, which avoided by fixing small pieces of model-merely reduces the copper without inling wax at the corners of the plate. If juring the lines, except the very pale intended to be etched on Hamerton's one; these must be etched over again. positive process, the drawing board, with It is better to have the plate over-bitten the well in it, must be taken, and the ne- than not enough, as the former is more cessary hydrochloric acid and chlorate of easily remedied than the latter. potash in two stoppered bottles. These Stippling is also executed on the etchcan be mixed with water when required. ing ground by dots instead of lines made Dry point is frequently used in the with the etching needle, which, according finishing of etched plates. The dry point to the intensity of the shadow to be reis an ordinary steel etching needle, sharp- presented, are made thicker and closer ened in a peculiar manner with a sharp The work is then bit-in. rounded cutting edge, and used without Etching on Steel is executed much in either etching ground or acid bath. By the same way as in the process on copper. using this tool on the bare copper, a burr The plate is bedded on common glaziers' is raised, which catches the ink, and in putty, and a ground of Brunswick black, printing gives the desired effect of a line or wax, is laid in the usual way, through
which the needle scratches. It is then | attack the glass where the way has been bitten-in in the way above described. removed only, and produce the dull ap
Etching on Cast Iron.—Use a solution pearance desired. The entire surface of of common salt and sulphate of copper for the glass can be rendered ground in the biting-in.
its appearance by exposing it to the Etching on Steel or Iron.—Take sul- fumes of the acid gas in its ordinary conphate of copper, sulphate of alum, and dition, unprotected by the wax. The muriate of soda, of each 2 drachms, and production of the gas is accelerated by strong acetic acid 1} oz., mixed together. | the warmth of a hob or of a spirit lamp First smear the part intended to be | applied to the bottom of the leaden vessel etched with yellow soap, and write with for a few moments. 2. To obtain the a quill pen without a split:
| liquid acid, place the mixture named ETCHING GLASS.--Glass is etched by above in a leaden retort, and conduct the hydrofluoric acid gas, or by liquid hydro- gas from the retort into a leaden bottle fluoric acid. The acid for this purpose containing some water, so long as the is obtained by treating fluoride of calcium, water absorbs the fumes. The water Derbyshire spar, with sulphuric acid, in becomes thus highly charged with hydroa leaden vessel, as we shall presently fuoric acid, and this liquid is to be used describe. The gaseous hydrofluoric acid in the second process. The glass plates has the property of producing a surface are to be prepared as before, with the which represents ground glass in its ap- addition of a small wall of wax or putty, pearance; but the liquid acid produces | which is to be formed round its edges ; just the contrary effect, and dissolves the liquid acid is poured upon the etched away the glass, leaving the surface waxed surface, and allowed to remain polished and clear Etching glass, there- until a sufficient depth of etching is fore, consists of two operations ;-etch produced. 3. To produce a colourless ing by the gas, and producing a dull pattern on a coloured glass ground, you opaque surface, and etching by the liquid, proceed as for etching an ordinary pane and producing a surface which is bright of glass, but the operation is conducted and clear. 1. Gaseous hydrofluoric acid is upon the surface of flashed glass; that the product of the action of sulphuric is, glass which is simply covered on one acid and fuoride of calcium. "Take of its sides with a colour, and which powdered fluoride of calcium, 2 parts; is not stained throughout. This flashed sulphuric acid, 3 parts. The powdered glass is a cheap imitation of stained glass; fluoride is placed in a leaden dish or the thin coating of coloured material is shallow box, the sulphuric acid poured soon dissolved by the acid, so as to leave upon it. By means of a stick, the acid a transparent or ground-glass pattern on is made into a paste with the powdered a coloured glass ground, according as the fluoride; the mixture only requires to s process is conducted by means of gaseous be warmed to evolve considerable fumes or liquid hydrofluoric acid. The acid of gaseous hydrofluoric acid. These fumes must be carefully handled, as it attacks are disagreeable; the experiment should, the skin and produces stubborn sores, therefore, be conducted in the open air or which are not easily healed, and it must under a chimney. The glass plate to be be kept in india-rubber bottles, as it will etched is covered with wax, by gently dissolve glass. warming the glass sufficient to melt wax, Engraving on Copper is perand rubbing it with a piece of white formed by cutting lines representing the wax until it is covered by a thin layer; subject on a copper plate by means of a it is then allowed to cool, and the waxed steel instrument, called a graver, or bursurface is etched with a graver. The in, ending in an unequal-sided pyramidal sheet of glass thus prepared is used as a point. Besides the graver, the other cover for the leaden vessel containing the instruments used in the process are a materials, with the waxed side presented / scraper, a burnisher, ac oil-stone, and a to the escaping fumes. These fumes will | cushion for supporting the plate. In
cutting the lines on the copper, the | the copper, on which the engraver prograver is pushed forward in the direction ceeds to execute his work. required, being held at a small inclination Engraving on Silver or Gold. to the plane of the copper. The use of -1. The engraving is first exposed to the burnisher is to soften down the lines the vapour of iodine, which deposits upon that are cut too deeply, and for burnish- the black parts only. The iodized ening out scratches in the copper; it is graving is then applied, with slight presabout 3 inches long. The scraper, like sure, to a plate of silver, or silvered the burnisher, is of steel, with three copper, polished in the same manner as sharp edges to it; it is about 6 inches daguerreotype plates. The black parts long, tapering towards the end. Its use of the engraving which have taken up is to scrape off the burr raised by the the iodine part with it to the silver, action of the graver. To show the ap which is converted into an iodide at those pearance of the work during its progress, | parts opposite to the black parts of the and to polish off the burr, engravers use design. The plate is then put in coma roll of woollen, or felt, called a rubber, munication with the negative pole of a which is used with a little olive-oil. small battery, and immersed in a satuThe cushion, which is a leather bag about rated solution of sulphate of copper, con9 inches diameter filled with sand, for nected with the positive pole by means laying the plate upon, is now rarely of a rod of platinum. Copper will be used except by writing engravers. For deposited on the non-iodized parts, corarchitectural subjects, or for skies, where | responding to the white parts of the a series of parallel lines are wanted, a engraving, of which a perfect representaruling machine is used, which is ex tion will thus be obtained ; the copper ceedingly accurate. This is made to representing the white parts, and the act on an etching ground by a point iodized silver the black parts. The plate or knife connected with the apparatus, must be allowed to remain in the bath and bit-in with aquafortis in the ordinary for only a very short time, for, if left way.
too long, the whole plate would become COPPER PLATE.—The plate must be covered with copper. The plate, after perfectly polished, very level, and free having received the deposit of copper, from any imperfection; to this must be must be carefully washed, and afterwards transferred an exact copy of the outlines | immersed in a solution of hyposulphite of the drawing. To do this the plate is of soda to dissolve the iodide of silver, uniformly heated in an oven or otherwise which represents the black parts; it is till it is sufficiently hot to melt white then well washed in distilled water, and wax, a piece of which is then rubbed over dried. 2. Heat a silver plate, previously it and allowed to spread, so as to form a coated with copper, to a temperature thin coat over the whole surface, after sufficient to oxidize the surface on the which it is left in a horizontal position copper, which successively assumes diftill the wax and plate are cold. A tracing ferent tints, the heating being stopped having been taken of the original design when a dark-brown colour is obtained. with a black-lead pencil on a piece of It is then allowed to cool, and the thin tracing paper, it is spread over the exposed silver is amalgamated--the plate face of the prepared plate, with the lead being slightly heated, to facilitate the lines downwards, and, being secured from operation. As the mercury will not comslipping, a strong pressure is applied, by bine with the oxide of copper, a design which operation the lead lines are nearly is produced, of which the amalgamated removed from the paper, being transferred parts represent the black, and the parts to the white wax on the plate. The of the plate covered with oxide of copper pencil marks on the wax are now traced represent the white parts. The amalgawith a fine steel point, so as just to touch mation being complete, the plate is to be the copper; the wax is then melted off, covered with three or four thicknesses of and a perfect outline will be found on gold leaf, and the mercury is evaporated
py brat, the gold only adhering to the are destroyed by heating the pieces in black parts. The superfluous gold must every direction over a gentle fire of charthen be cleared off with the scratch,coal, breeze, or spent tan. A muffle furbrush; after which the oxide of copper nace, heated up to a dull red heat, is is dissolved by a solution of nitrate of preferred ; but small articles may be silver; and the silver and copper under- cleansed in a hot revolving cylinder. This neath are attacked with dilute nitric acid. operation is not adapted to very delicate Those parts of the design which are pro | articles, or for table-forks and spoons, lected by the gold, not being attacked, which must keep their toughness, or tó correspond to the black parts of the those pieces in which the different parts plate; the other parts, corresponding to are united by soft solders. Boil such the white parts of the engraving, may be articles in a solution of potash or soda, sunk to any required depth. When this which renders the fatty substances sooperation is completed the plate is finished, luble in water. This is done in a cast-iron and may be printed from in the ordinary kettle, provided with a cover, where method of printing from woodcuts. there is a boiling concentrated solution
Line Engraving on Gold.-| of carbonate of potash, or soda, or of To obtain from the same prints plates American potash. The caustic potash or with sunk lines, similar to the ordinary soda must be dissolved in ten times its engraved copper-plates, a plate of copper, weight of water. This solution lasts a covered with gold, is operated upon. On | long time: when it has lost part of its immersion in the sulphate of copper solu- | power, it may be revived by a few frag. tion, the parts corresponding to the white ments of caustic alkali. At the boiling parts of the engraving will become covered | point it will cleanse copper in a few with copper. The iodine, or compound seconds. If the articles to be scoured of iodine, formed, is then to be removed are joined with tin solder, they must not by the hyposulphite; the layer of de- be allowed to remain too long in the posited copper is oxidized, and the gold caustic liquor, which would dissolve the amalgamated, which may be removed by solder and blacken the copper. means of nitric acid, the oxide of copper Dipping. The pieces are then dipped being dissolved at the same time. In in a mixture of from 5 to 20 parts in this instance the original surface of the weight of sulphuric acid at 660 Baume plate corresponds to the white parts of for 100 parts of water. Most of the the print, and the sunk, or engraved, por- pieces to be cleansed may be dipped hot tions to the black parts, as in ordinary in this mixture ; but certain alloys, in copper-plate engravings.
which tin, zinc, or antimony predominate, Electro-metallurgy. The first such as cast bronze, must not beso treated, and most. important operation in all as the sudden cooling will occasion cracks branches of the electro-deposition of one and flaws. Copper articles may remain metal upon another, is to effect a thorough any length of time in the dipping bath; and chemical cleansing of the surface of they should not be removed before the the metal upon which the coating is to black coat of binoxide of copper, caused be deposited.
| by the heating, is entirely dissolved. The CLEANSING COPPER AND ITS ALLOYS. | remaining coat of red protoxide of copper - This is done in six operations. 1. is unacted upon by the sulphuric acid. Cleansing by fire, or by alkalies. 2. Articles having parts made of iron or Dipping. 3. Dipping in old aquafortis. zinc must not be submitted to the action 4. Dipping in new aquafortis and soot. of dilute sulphuric acid, or they will be 5. Dipping in compound acids for a entirely dissolved; therefore avoid the bright or dead lustre. 6. Dipping in use of implements or wires of iron, zinc, nitrate of binoxide of mercury.
or steel. A dipping bath which contains Cleansing by Fire, or by Alkalies.- copper in solution from previous operaThis is to remove any foreign substances, tions will not suit for articles which may especially those of a fatty nature, which contain iron, tin, tin solder, antimons,