Imagens da página
[merged small][ocr errors][merged small]

small shaving is rather ploughed out than cleanly cut out; and the force necessary to push the tool forward frequently causes small pieces to fly out at each side of the hollowed line, more especially if the wood is dry. The shaving, also, instead of turning aside over the face of the tool, turns over before the point, as in Fig. 38, and hinders the engraver from seeing that part of the pencilled line which is directly under it. A short-faced tool of itself prevents the engraver from distinctly seeing the point. When the face of a tool has become obtuse it ought to be ground to a proper form; for instance, from the shape of the figure A to that of B, Fig. 39.

[ocr errors][ocr errors][ocr errors][merged small]

oil, or allowed to cool gradually. If removed from the iron while it is still of a straw colour, it will have been softened no more than sufficient; but should it have acquired a purple tinge, it will have been softened too much, and instead of breaking at the point, as before, it will bend. A small grindstone is of great service in grinding down the faces of tools that have become obtuse. A Turkey stone is a very good substitute, as, besides reducing the face, the tool receives a point at the same time; but this requires more time. Some engravers use only a Turkey stone for sharpening their tools; a hone in addition is of great service. A graver that has received a final polish on a hone cuts a clearer line than one which has only been sharpened on a Turkey stone; it also cuts more pleasantly, gliding smoothly through the wood, if it be of good quality, without stirring a particle on either side of the line. The gravers and tint-tools used for engraving on a plane surface arc straight at the point, as are here represented, Figs. 40 and 41; but for engrav

ing on a block rendered concave in certain parts by lowering, it is necessary that the point should incline slightly upwards, as in Fig. 40. The dotted line shows the direction of the point used for plane surface engraving. There is no difficulty in getting a tool to descend on one side of a part hollowed out or lowered ; but unless the point is slightly inclined upwards, as is here shown, it is extremely difficult to make it ascend on the side opposite without getting too much hold, and thus producing a wider white line than intended.

Gouges and Chisels, A to E, Fig. 42.— Gouges of different sizes are used for scooping out the wood towards the centre of the block; whilst flat tools, or chisels, are chiefly employed in cutting away the

[merged small][ocr errors][ocr errors][merged small][graphic][merged small][graphic][merged small]

ing against the side of the block, in the manner just represented, allows the blade to move backwards and forwards with a slight degree of pressure against it, and in case of a slip, it is ever ready to check the graver's progress. This mode of resting the thumb against the edge of the block is, however, only applicable when the cuts are so small as to allow the graver, when thus guided and controlled, to reach every part of the subject. When the cut is too large to admit of this, the thumb then rests upon the surface of the block, as in Fig. 45,

Fio. 45.


still forming a stay to the blade of the graver, and checking at once any accidental slip.

Wood.—For large coarse cuts, such as are often used for trade purposes, sycamore and pear tree may be employed, but are too soft and irregular in the grain to bear fine work. Boxwood, either English, American, or from the Levant, is the favourite material; it should be of a light straw yellow colour, free from black or white spots or red streaks, as these indicate a soft wood, which crumbles away under the graver. The small wood is generally tolerably free from blemishes. When a large cut is wanted, if a block of the required size is not at hand, several smaller blocks are sometimes bolted together. The blocks are cut a trifle thicker than the height of type, about an inch; they are then planed, brought to a very smooth surface, and gauged to the exact height ot type. These blocks should be kept for some months until they are properly seasoned.

Drawing on the Block.—The polished boxwood will not take the pencil without a slight wash is first laid on it. A thin wash of Chinese white mixed with water, some very fine Bath brick dust, or the white scrapings of glazed cardboard, mixed with water, and gently rubbed off when dry with the palm of the hand, gives a capital surface for the black-lead pencil. Make a tracing of the outline of the subject, place a sheet of transfer paper on the block, lay the tracing over it, and go carefully over every line with a sharp point. It must be remembered that the woodcut will be reversed when printed. The outlines must be corrected, and completed, by a hard sharp-pointed H H H H pencil; the tints may afterwards be filled in by a softer pencil, or thin washes of Indian ink, to show the effect of light and shade. Caution must be taken to use these washes sparingly, so as not to affect the wood. All parts of the block, not being cut, must be kept covered up, so as to preserve the drawing from injury, and the fine lines of the cut from being blunted or broken. Smooth blue glazed paper is very good for this purpose, as it reduces the glare from the lamp.

Proofs. When the engraving is finished, a proof may be taken in the following manner before blocking out the cut, that is, before the superfluous wood is cleared away; — rub down a little printer's ink on a slab till it is fine and smooth; take a little of this on a silk dabber, and carefully dab the block until sufficient ink is left upon the surface, without allowing any to sink below it. Lay a piece of India paper on the block with about two inches margin all round; on this place a thin smooth card; rub this over with the burnisher, taking care not to shift the card or paper.

Plugging.—If a slip, or mistake, occurs in a woodcut, it may be remedied by the insertion of a plug. A hole must be drilled in the block; if the error is a small one the hole need not be deep, but if a large piece has to be inserted it must be deeper in proportion. A plug is cut, of a round, taper shape; the small end is inserted in the hole, and the plug is driven down, without, however, using too much force. The top of the plug

must then be cut off, and carefully brought to a smooth surface, level with the rest of the block; if this is not done the plug will be visible on the print. If the error to be remedied happens to be in a long line, a hole must be drilled at each end, and the wood between the two holes removed by small chisels, the hollow space being filled up in a similar way to that already described.

Lithography.—The following are the principles on which the art of lithography depends ; — the facility with which calcareous stones imbibe water; the great disposition they have to adhere to resinous and oily substances; and the affinity between each other of oily and resinous substances, and the power they possess of repelling water, or a body moistened with water. Hence, when drawings are made on a polished surface of calcareous stone, with a resinous or oily medium, they are so adhesive that nothing short of mechanical means can effect their separation from it; and whilst the other parts of the stone take up the water poured upon them, the resinous, or oily parts, repel it. When, therefore, over a stone prepared in this manner, a coloured oily or resinous substance is passed, it will adhere to the drawings made as above, and not to those parts of the stone which have been watered. The ink and chalk used in lithography are of a saponaceous quality; the former is prepared in Germany from a compound of curd or common soap, pure white wax, a small quantity of tallow and shellac, and a portion of lampblack, all boiled together, and, when cool, dissolved in distilled water. The chalk for the crayons used in drawing on the stone is a composition consisting of the ingredients above mentioned. After the drawing on the stone has been executed, and is perfectly dry, a very weak solution of nitric acid is poured upon the stone, which not -*nly takes up the alkali from the chalk or ink, as the case may be, leaving an insoluble substance behind it, but lowers, to a small extent, that part of the surface of the stone not drawn upon, thus preparing it to absorb water with greater freedom. Weak gum water is then applied to the stone, to close its pores and keep it moist. The stone is now washed with water, and the printing ink applied with rollers, as in letterpress printing; after which it is passed, in the usual way, through the press, the processes of watering and inking being repeated for every impression. If the work !is inclined to get smutty a little vinegar or stale beer should be put into the water that is used to damp the stone.

There is a mode of transferring drawings made with the chemical ink on paper prepared with a composition of paste, isinglass, and gamboge, which, being damped, laid on the stone and passed through the press, leaves the drawing on the stone, and the process above described for preparing the stone and taking the impressions is carried into effect.

Lithographic Stokes, To Prepare. —Stones are prepared for chalk drawings by rubbing two together, with a little silver sand and water between them, taking care to sift the sand to prevent any large grains from getting in, by which the surface would be scratched. The upper stone is moved in small circles over the under one till the surface of each is sufficiently even, when they are washed, and common yellow sand substituted for the silver sand, by which means is procured a finer grain. They are then again washed clean, and wiped dry. It will be found that the upper stone is always of a finer grain than the under one. To prepare stones for writing or ink drawings, they are rubbed with brown sand, washed, and powdered pumice-stone used instead; the stones are again washed, and each polished separately with a fine piece of pumice-stone, or water Ayr-stone. Chalk can never be used on the stones prepared in this manner. The same process is followed in order to clean a stone that has already been used.

Lithographic Ink.—Tallow, 2 oz.; virgin wax, 2 oz.; shellac, 2 oz.; common soap, 2 oz.; lampblack, J oz. The wax and tallow are first put in an iron saucepan with a cover, and heated till they ignite; whilst they are burning the soap must be thrown in in small pieces, one at a time, taking care that the first is melted

before a second is put in. When all the soap is melted the ingredients are allowed to continue burning till they are reduced one-third in volume. The shellac is now added, and as soon as it is melted the flame must be extinguished. It is often necessary in the course of the operation to extinguish the flame and take the saucepan from the fire, to prevent the contents from boiling over; but if any parts are not completely melted, they must be dissolved over the fire without being again ignited. The black is now to be added. When it is completely mixed the whole mass should be poured out on a marble slab, and a heavy weight laid upon it to render its texture fine. The utmost care and experience are required in the making both the ink and chalk, and even those who have had the greatest practice often fail. Sometimes it is not sufficiently burned, and when mixed with water appears slimy: it must then be remelted and burned a little more. Sometimes it is too much burned, by which the greasy particles are more or less destroyed; in this case it must be remelted, and a little more soap and wax added. This ink is for writing or pen-drawing on the stone. The ink for transfers should have a little more wax in it.

Lithographic Chalk.—Common soap, 1J oz.; tallow, 2 oi.; virgin wax, 2 J oz.; shellac, 1 oz.; lampblack, J oz. Mix as for lithographic ink.

Lithographic Transfer Paper.— Dissolve in water J oz. gum tragacanth. Strain and add 1 oz. of glue and J oz. of gamboge. Then take 4 oz. French chalk, Joz. old plaster of Paris, 1 oz. starch; powder, and sift through a fine sieve; grind up, with the gum, glue, and gamboge; then add sufficient water to give it the consistence of oil, and apply with a brush to thin sized paper.

Transferring. — The drawing or writing made on the prepared side of the transfer paper is wetted on the back, and placed, face downwards, on the stone, which must previously be very slightly warmed, say to about 125° F. Pass the stone through the press four or five times, then damp the paper, and carefully remove it.

Drawing On Stone. — The subject should first be traced on the stone in red, great care being taken not to touch the stone with the fingers. Or the drawing may be done by means of a black-lead pencil; but this is objectionable, as it is difficult to distinguish the line from that made by the chalk or ink. Then, having a rest to steady the hand, go over the drawing with the chalk, pressing it with sufficient firmness to make it adhere to the stone. For flat tints, considerable practice is necessary to secure an even appearance, which is only to be obtained by making a great many faint strokes over the required ground. Lights may Dither be left, or, if very fine, can be •craped through the chalk with a scraper. If *ay part is made too dark, the chalk must be picked off with a needle down to the required strength.

Etchinq-in, Foe Printing On Stone. —Dilute one part of aquafortis with one hundred parts of water. Place the stone in a sloping position, then pour the solution over it, letting it run to and fro until it produces a slight effervescence. Then wash the stone with water, and afterwards pour weak gum water over it. The acid, by destroying the alkali on the lithographic chalk, causes the stone to refuse the printing ink except where touched by the chalk; the gum water fills up the pores of the stone, and thus prevents the lines of the drawing from spreading. When the stone is drawn on with ink, there must be a little more acid used with the water than when the drawing is made with chalk. The roller charged with printing ink is then passed over the stone, which must not be too wet, and the impression is taken as before described.

Engraving On Stone.—The stone must be highly polished; pour the solution of aquafortis and water over it, washing it off at once. When dry, cover with gum water and lampblack; let this dry, then etch with a needle, as on copper. It is necessary to cut the surface of the stone through the gum, the distinction of light and dark lines being obtained by the use of fine or broad-pointed needles. Rub all over with linseed oil, and wash

the gum off with water. The lines on the stone will appear thicker than they will print.

To Imitate Woodcuts on Stone.—Cover with ink those parts meant to be black; scratch out the lights with an etching needle; the lines which come against a white background are best laid on with a very fine brush and lithographic ink.

Inking Roller.—Fasten a smooth piece of leather round a wooden roller of the required length.

Removing the Transfer.—The existing transfer is ground away by rubbing it with another piece of stone, putting sand between, like grinding flour between the millstones, using finer sand as it gradually wears away; then it is ground with rotten-stone till of the requisite fineness for the next transfer.

Transferring from Copper to Stone.— In transferring from «opper to stone use prepared paper, that is, ordinary unsized paper, coated with a paste of starch, gumarabic, and alum. Take about 60 parts of starch, and mix with water to a thinnish consistency over a fire; have twenty parts of gum ready dissolved, and also ten parts of alum dissolved; when the starch is well mixed, put in Lfte gum and alum. While still hot, coat the paper with it in very even layers, dry, and smooth out. Take an impression from the copper with the transfer ink; lay the paper on the stone, damp the back thoroughly with a sponge and water, and pass through the lithopress. If all is right, the impression will be found transferred to the stone, but it will of course require preparing in the usual manner. The great advantage gained is, that very many more impressions may be printed from stone than from a copper plate, and very much quicker.

Engraving on Steel is the same as copper-plate engraving, except in certain modifications in the use of the acids; therefore, so far as the process is concerned, no particular description is necessary; but the means employed for decarbonizing and recarbonizing first the steel plate, so as to reduce it to a proper state for being acted upon by the graving

« AnteriorContinuar »