CHAPTER VIII.ETCHING LINE TRANSFERS.
For etching transfers on zinc, whether photographic or direct, we shall require the following apparatus: A slab of iron about 24 × 18 inches and1⁄2or 1 inch thick, supported horizontally upon four legs, and heated by an atmospheric burner, arranged somewhat like a gridiron so that the heat is even all over. A set of rollers on litho stock, one of leather, one of flannel, and one or two glazed rollers, the same as lithographers use for tint printing—we also require an etching box—i. e., a wooden tray, 30 × 24 inches, and 8 inches deep, well made of seasoned wood, lined with either pitch (with a little tallow added), or gutta-percha, and mounted upon rockers.
This box will require a firm table for its support during the etching, said table standing as close as convenient to a sink and water tap.
The other requisites used during etching, are, nitric acid, turpentine, gum Arabic of a good quality, some powdered nutgalls, three or four sponges, some finely powdered resin, a flat camel’s-hair brush, a solution of shellac in spirits of wine, and the following inks:
First the etching ink, composed of beeswax one-quarter ounce, Russian tallow two ounces, bitumen half an ounce, middle varnish two ounces.
Melt these together in a pan over a fire, or Bunsen burner, stirring well during the operation, so as to mix them thoroughly; when all are melted, add five ounces of ordinary letterpress printing-ink, and thoroughly mix; then allow to boil and continue the heat until the gas escaping from the bursting bubbles explodes upon the application of a lighted taper; then remove all from the fire, and allow to cool.
For a hard ink, for use after the plate is etched deep enough, and the resist is cleaned off, mix
Beeswax1⁄2ounce.Resin1ounce.Shoemaker’s Wax1ounce.Black Litho Ink (about $1 a pound)2ounces.
Beeswax1⁄2ounce.Resin1ounce.Shoemaker’s Wax1ounce.Black Litho Ink (about $1 a pound)2ounces.
Melt, then cool and mix with turpentine to make it the consistency of soft soap.
Now, with these and a solution of gum Arabic (in cold water), the thickness of cream, add one-quarter pint of a decoction of nutgalls to each quart of gum solution. The decoction of nutgalls is made by adding one-quarter pound of bruised nutgalls to one and one-half pints of water, in an earthenware vessel (not metal); boil, then allow to stand at the fire and simmer gently for six hours, keeping the vessel covered over; then allow to cool, filter and add the proper quantity to the above gum solution.
We will assume that a suitable place is provided for carrying on the operations to be described, in the shape of plenty of bench room, and a good light to work by.
The first stage in etching a zinc plate in relief is, to slightly warm it upon the hot plate, then allow it to cool (by-the-bye, it will be very convenient to have a clean litho stone handy for placing the plate upon to cool quickly). The plate being cold, with a piece of soft sponge carefully smear it over with the gum solution, allow the gum to dry, spontaneously, in a cold current of air; if heat be applied the gum will crack and bring away the image from the plate.
Whilst the gum is drying, with a palette knife place equal parts of transfer ink (page44) and of etching ink (page54) upon one corner of the inking slab, then thin to the consistency of cream, with middle varnish, thoroughly incorporating the three ingredients with the palette knife.
Now place a little of this ink upon the leather roller and roll vigorously upon the slab, so as to distribute the ink thoroughly upon both roller and slab; be careful not to get too much ink on the roller, nor to have it too thin; in fact, work the ink as stiff as is possible.
Now lay the zinc upon a piece of clean paper, and sponge it gently over with a wet sponge, so as to loosen the film of gum, then squeeze the sponge nearly dry, and pass it over the plate again, so as to insure it being evenly damp all over, but be careful not to make it too dry.
Now proceed to roll up, by passing the charged roller to and fro over the plate, using moderate pressure and slow motion, recharging the roller at short intervals from the inking slab. Occasionally use the damp sponge so as to keep the plate sufficiently damp to resist the ink.
If the roller slides instead of rolling, wipe it with an old linen rag, which will remove the moisture; then recharge the roller again upon the slab.{57}
The rolling is continued until the whole image is an intense black, when it is carefully dusted over with very finely powdered resin applied with a broad camel’s-hair brush, taking care that all the image gets covered. Then rub it gently with a wet, soft sponge and place it in the etching box containing a mixture of water and nitric acid, the acid being only just perceptible to the taste.
The plate should remain in this for one minute (the box being kept rocking); it is then removed, and thoroughly washed back and front under the tap. Rub it gently with a clean soft sponge.
This etching is merely to remove any traces of gum or dirt from the zinc which would interfere with the shellac varnish holding.
Now dry the plates, using gentle heat, then coat the back with thin shellac varnish to protect it from the acid; do the same to the margin of the picture on front, also varnish the centre of any very broad whites up to half an inch of the image, so that the acid dissolves no more zinc than is necessary. Now examine the image carefully, and if any of the lines are defective touch them up, and make any alterations and additions required.
The plate is now ready for the first etching, for which purpose a little nitric acid is added to the water in the etching tray—precise directions cannot be given as to how much acid to add, as so much depends upon the area of zinc on the plate that requires dissolving; practice, however, will soon enable the operator to judge the proper quantity. If too much acid is added, the plate will quickly be covered with myriads of minute bubbles, in which case it must be instantly removed, well washed, and the bath diluted with water before the plate is reimmersed. If, on the other hand, there is too little acid present, the action is too slow, and more must be added.
The first etching must be carefully watched, and the rocking continued, until the application of the finger-nail to the margin shows that the zinc inside has been dissolved away to a depth of about the thickness of a visiting card.
The first etching is the most important of the whole, as unless a sufficient depth be attained the sharp lines will not be obtained; and as the ink is not yet capable of resisting too strong acid, great care must be taken that the work is not damaged; proceed cautiously, adding acid from time to time as required.
As a rule, the first etching will take from five to ten minutes (the tray being kept rocking all the time).
When it is judged that the first etching has been carried far enough, remove the plate from the tray, wash it well under the tap, rubbing gently with a{58}sponge, so as to remove the scum left by the acid, dry by means of gentle heat, then allow it to cool.
When the plate is quite cold, smear it over with gum solution, and with a piece of cardboard, fan the gum dry.
Now sprinkle the inking slab with turpentine, and with a cloth wipe the slab clean. Take a piece of etching ink and thin it with middle varnish, mixing them well with the palette knife upon the slab; now take the leather roller, and with the palette knife place a little of the ink upon it, and roll up on the slab until both roller and slab are well coated; but on no account must there be too much ink, nor must it be too thin.
Now lay the zinc down on the bench, on a piece of clean paper, and with the wet sponge carefully wash off the gum; then wipe all superfluous water off the plate, and roll up with the leather roller charged as above; roll the plate first one way, and then the other, keeping the zinc evenly damp all over, else the ink will catch in the whites, and probably spoil the picture. When the rolling is completed, and as much ink as possible has been piled on, the zinc will be nearly dry. If not, allow it to stand in a cold current for a little time, then take it to the drawer in which the powdered resin is kept, and smear the plate all over with the powder. Now brush as much of the resin away as will come, using the brush from all sides, so that all the lines get evenly coated, not only on the top, but upon the sides; this being done, take a damp sponge and carefully remove the superfluous resin from the whites, or unprotected zinc.
The plate is now ready for the second etching, and the solution in the etching tray must be reinforced by the addition of a little acid; but do not add too much at once. It will be far best to add a little at a time, and then, as soon as the zinc shows there is no action going on, add a little more; an easy and simple method of ascertaining whether any acid be present or not is to wipe the bare metal with the tip of the finger, and if that spot (which will be brighter than the surrounding parts) does not speedily resume its dingy color, the acid is exhausted.
The plate being immersed in the solution, set the tray rocking, and pay attention to the remarks above. At the end of ten minutes remove the plate from the tray, wash it under the tap, rub it gently with soft sponge, then remove as much of the water as possible, and examine the progress made by the acid. This can be seen by the lines being bare below the ink, in which case the etching has been carried far enough, and if not stopped, there would be danger{59}of under-cutting; if, however, no progress has been made, add a little more acid to the solution, replace the zinc, and rock again for another five or ten minutes.
The second etching being effected, the zinc is carefully washed, and the scum left by the acid is carefully sponged away; now stand the zinc up near the hot plate, so that it will get the benefit of a gentle heat, and when quite dry lay it upon the hot plate (which should be heated to a temperature of 120° to 150° F.) face up, with a piece of brown paper between the zinc plate and the hot plate.
As soon as the zinc plate begins to get hot, there will be a tendency to curl slightly away from the hot plate, which, if allowed, would prevent the ink being evenly melted. To prevent this, take a brad-awl in each hand, and press down the sides of the zinc, taking care not to touch any of the picture.
Allow the zinc to remain on the hot plate until the ink and resin are melted and run down to the bottom of the etching, then remove it and lay it on the cold slab until the plate is cold.
When cold, smear the plate with the gum solution, fan it dry (never use heat for drying the gum), moisten with wet sponge, roll up again (use the leather roller), using the ink pretty stiff on the inking slab; keep the surface of the zinc well moistened. When the roller gets too much water upon it, pass a piece of damp cheese-cloth over it to remove the water; then roll the roller vigorously on the slab until it again bites the ink. Continue rolling the zinc until all portions have received due attention from the roller. N. B.—Some of the closest work will be quite blocked up this time, and each subsequent rolling will block up more and more, until only the very open work will be left.
Now allow the zinc to get dry, then cover it with resin, brushing from all sides, so as to coat the sides of the lines as well as the top, and then remove all superfluous resin from the whites with a damp sponge. The zinc is now ready for the next etching, for which more acid is added to the solution in the etching tray.
Rock the tray carefully, watching the zinc to see that the acid is neither too weak nor too strong, until the progress can be seen by examining the plate; the time, with the proper quantity of acid, is twenty to thirty minutes.
When the etching has proceeded far enough, after washing and sponging, again allow it to dry, then place it upon the hot plate until the ink is melted and runs down the sides of the lines; then cool, smear with gum, fan dry, moisten with sponge, and roll up as before; dry, cover with resin, using a{60}camel’s-hair brush, then dampen with a sponge and give a fourth etching, using the same precautions as to strength of acid and duration of rocking as before.
Now cool the plate; get a little more ink on the roller, and roll the plate whilst cold. When the surface of the lines has a nice even coat of ink upon each and all (coarse and fine), again warm the zinc on the hot plate until it is just too hot to hold in the fingers; then cool it again, varnish the back with shellac varnish, then make a mark with a blunt point, in the ink on the margin, so as to lay a short line of zinc bare to the action of the acid.
The round of operations is repeated; but for rolling up for the fifth and subsequent etching, a flannel roller is used, and more ink will be required upon the slab; it will also require to be a little thinner.
For some subjects six or seven etchings will be required, whilst for others—especially where there are whites that are too small for cutting out with a fret saw or router—ten or twelve etches will be required. Practice, the best teacher, will soon enable the operator to judge how many are required.
The etching having been carried as deep as is judged sufficient, sprinkle the plate liberally with turpentine, and with a stiff scrubbing brush loosen the ink from the lines, and wash it off with a solution of American potash.
The plate being cleared from all ink, etc., is now examined carefully. The sides of the lines will show each etching, by a series of irregular steps. If the plate be put into the press in this condition, the chances are that before many copies had been made, these steps would take more or less ink from the rollers, and blur the image; therefore, before passing it into the hands of the printer, the plate will require etching two or three times more, to get rid of these irregularities.
This is done by warming the zinc on the hot plate, and then, whilst still warm, rolling up with a fine glazed roller charged with the hard etching ink from a clean inking slab.
Roll the zinc firmly, first one way and then the other, so that all the tops of the lines get well coated with ink; now make a mark on the margin with a blunt point in the ink, so as to lay a short line of zinc bare to the action of the acid.
Next empty the etching tray, put into it some clean water, and add sufficient acid to make it taste like strong vinegar; in this immerse the plate, and keep rocking for ten or fifteen minutes, or until the mark on the margin, when felt with the finger-nail, shows that it has attained a depth about the same as that obtained in the first etching.{61}
Now wash the plate under the tap, and wash off the ink with turpentine, followed by a solution of American potash; again wash and dry on the hot plate. Now examine, and if the lines are free from the steps, the plate is finished, but if not, the operation must be repeated until the steps are all removed.
Be careful to cover the surface of the block thoroughly with the ink, else the acid will spoil the picture.
The plate is now ready either for mounting for the press, or for electrotypes being taken from it; if the former, the deep whites are cut away with the router or fret saw, the edges are trimmed or bevelled, holes are drilled and counter-sunk at convenient places, for the insertion of nails or screws to fix the zinc to the wooden block, to make the surface type high.
The object aimed at in the instruction in Part I. is the production of relief blocks on zinc from an original in black and white, which original may be a drawing made purposely for reproduction, or it may be from a drawing already in existence, a woodcut, or engraving, the picture being rendered entirely in line, or a chalk drawing may be used. In fact, any subject that is capable of being worked from either at a type press or by ordinary (monochrome) lithography. Washed drawings, or oil or water color drawings are not applicable.
In fixing plans, or drawings on the easel, prior to photographing them, if they are cockled, and difficult to get flat, pins may be placed anywhere, so long as the lines are not interfered with, for these pins may be painted out with a camel’s-hair brush and gamboge or Indian ink. It is important that the plans or drawings be as flat as possible, as if the lines are cockled, they will not be photographed straight.
In photographing drawings on tracing paper or cloth, a piece of white paper should be placed behind them.
When, from an original of black lines on a white ground, it is desired to make a reverse block—i. e., white lines on a black ground—a negative is first made from the original, and from that negative a transparency is made; and a print made upon the zinc from that transparency will be a reverse of the original.
Thus far I have tried to make plain the details of a process which is as fascinating and as pretty as any in photography, and which supplies results which could not be attained by the most expert workers two years ago. And since those experts first obtained even tolerable results by zinc etching, like{62}everything else in photography, it has made wonderful progress. At first we were delighted and content when a block was obtained with relief sufficient to enable us to print it upon an ordinary press with type. But now we can get from the zinc surface all the qualities which are given by the lithographic stone. Indeed, the process of zincography bears a very strong general resemblance to that of lithography; of course, it varies therefrom in matters of process detail. The manipulations of zincography, however, are no more complicated in their nature than the details of printing, etc., from stone. Crayon drawings, ink work in line and stipple, rubber work, in fact, anything that can be drawn on stone can be drawn on properly prepared zinc, with the exception of engraved lines (intaglio), the structure of the zinc not giving the yielding brittleness of stone. The great departure made possible by zinc plates exists in the fact that they can be bent to the surface of a cylinder, thus displacing the reciprocating bed and stop-cylinder of the lithographic press with the continuously rotating plate and impression cylinder of the zincographic press, which, at the same driving speed, produces double the number of impressions printed on the lithographic press. To Mr. Bernard Huber, of the Huber Printing Press Company of Taunton, Mass., belongs the credit of designing the only American zincographic press in existence, and which is now in successful operation in several lithographic establishments. It is a thoroughly American machine in design and construction, and while no glowing prophecies of its immediately taking the place of lithographic presses are indulged in, yet this kind of press has its place and use, and will by its qualities win favor in the trade.
Many lithographers are beginning to give correct attention to zincography, but few are willing to give the time and constant experimenting to the subject that has been given by Messrs. Harris & Jones, who during the past three years have operated the zincographic presses in their lithographic establishment known as the Providence Lithograph Co. Having taken the selling agency of the Huber zincographic press, they offer to those whobuythe press full instructions in zincographic surface printing.
These suggestions are given right here, first because we are now about to take a step higher in zinc etching—a step which will lead us to results which lithography can scarcely equal in some particulars—and second, because it is the policy of this work to withhold no information which the novice will need in supplying himself with a perfect outfit for doing the best of work. For the same reason the advertisers have been chosen, rather than received in the usual way.