CHAPTER V.THE TRANSFER OF THE DRAWING, AND ITS TREATMENT BEFORE ETCHING.

According to the methods of producing them, classify the drawings as follows:

(a) Freehand drawings in crayon or ink, drawn with lithographical chalk on rough paper, or with pen and chemical Indian ink on paper prepared for transferring.

(b) Lithographical transfer of engravings, pen-and-ink crayon drawings, or drawings on stone.

(d) Anastatic transfers.

(e) Fat or resin prints from photographic negatives.

Proceed as follows:

(a)Transfer of hand-drawing.—Place the drawing to be transferred with its face upon a sheet of clean, white paper, and moisten the back with a weak solution of nitric acid (1⁄2° Baumé), by means of a sponge. Over-moistening causes obliteration of the drawing, fringing of the single lines, and the running together of the hatched portions. The correct degree of moisture can be ascertained when the side prepared and drawn upon grows slightly sticky, and when the drawing becomes glossy. This will take place in from four to five minutes after moistening. This time is to be spent in arranging the zinc in the press, after having freed it from all greasiness. Place a card on the rolling press below the drawing and the zinc; above it, a sheet of good blotting-paper, a sheet of Bristol paper and are of pressing board; then make a trial print with the press, a clean piece of paper taking the place of the drawing. The correct pressure is a matter of experience; it is advisable to begin with a pressure less by one sheet, in order to be able to increase it during the process of transfer.

In the lithographic press the ink-block is first to be adjusted; since it needs a greater “setting in” than the rolling press, the zinc must be cut larger. It must extend three centimetres on all sides beyond the drawing. The edges of the cut plate must be well ground off, in order that the ink-block may not be{74}caught; at all events, it is advisable to have the latter smaller than the plate. Observe that the range of the press should be regulated; then place the zinc directly, without any intervening layer of paper, on a solid stone; lay upon it a clean sheet of paper, a blotter, a sheet of Bristol paper, and a pressing board well covered with tallow. Make a trial by drawing the sheet through at a moderate pressure. If all is arranged, the work of transfer can be started. The temperature of the zinc should now be about 35° C.

Place the drawing down carefully, without moving it about; upon it the blotter, the Bristol paper, and a pressing board, and draw it through three times with constantly increasing pressure; turn the plate in a contrary direction, and draw it through three times in the same manner. Now place a moistened sheet of good paper between the blotter and the drawing, and draw through, first with weak, and then with strong pressure, three times in both positions. Instead of turning the zinc, the ink-block may be reversed. This finishes the operation of transprinting, and the next question is the loosening of the paper from the zinc. Here we can pursue two methods: first, we can have hot water and a porcelain tray at hand; place the copied plate in the tray, and pour the water upon it. The coated layer bearing the drawing begins to separate from the paper. Shaking the tray promotes this action, and soon the paper will loosen itself from the layer which remains attached to the zinc. With the second method proceed thus: moisten the back of the copied drawing, thoroughly with a sponge and cold water; allow it to soak in, warm the plate to 60°–65° C. and carefully rub all parts by hand. The layer will again separate by degrees from the paper, which latter we can then easily lift off from the plate.

On account of the strongly gelatinous layer, crayons on grained paper should only be moistened moderately before and after the first rolling, in order to avoid the coiling of the paper.

Hand-drawings on paper without coloring require treatment with stronger acid (I recommend nitric acid, 4° Beaumé). At the same time the drawing should be cut as close as possible. To draw it through securely, place it as usual upon the zinc, and above it a piece of prepared copy paper moderately moistened, and a trifle larger than the drawing, then a blotter, a Bristol board, and a thick card, and draw through as before. The coated copy paper sticks tight to the zinc after the first rolling; it also retains the drawing in its first position, and allows repeated rolling. If the original was over-moist when{75}copying, it sticks to the zinc and separates with difficulty; if the moistening was just right, two perfect copies can often be made from the same original.

I have attempted to copy drawings on a fatty zinc surface, and to etch them strongly, but, far from being satisfied with the result, I prefer the above method.

(bandc) Copies of lithographs, type, plates for printing of any kind, plates fordeepprinting, I make on well satinized copying paper*; in making the prints, I employ a copying ink as thick as possible, with the addition of a few drops of a thick solution of asphaltum in lavender oil, rolling a long time with but little color, so as to get a sharp rather than a heavy print.

* Instead of the paste-gelatine-chalk, I prefer to prepare the surface with a decoction of semina psyllii.

Plates fordeepprinting, I heat equally throughout before applying the color. Instead of color, I rub them with chemical Indian ink, wipe the surface carefully, even polish it finally with a ball and some Frankfort black. I then draw it through and again heat it uniformly, so that the copy comes off of itself. Fine, sharp transfers, with perfect relief, are thus obtained.

(d) Anastatic copies are no longer of great value, since they always turn out roughly and cannot compare with photographic copies. Although I possess a safe method, I believe that I will have to omit it on account of the limited space of my work and the minute importance of the results.

(e) Photographic fat or resin prints should be treated like ordinary prints. Moisten them on the back with water—which is preferable to placing them between moistened blotting-paper, since the drawing does not grow too wet—and wait till they are easily flexible. Drops of water on the film can and often do destroy the proof. Draw the plate through with increasing pressure and one intermediate moistening. Prints in fatty inks necessitate a temperature of plate of 35° C. Prints with dissolved etching varnish (resin) as a printing film should have from 50°–60° C. When loosening the paper avoid warming, but moisten well. Sticking of the gelatine film happens, especially with Husnik’s paper; a safe remedy is to dry the copy in strong light, after developing. Old sensitized paper, on the contrary, seldom sticks at all, and fresh paper should always be sought.

In printing with the rolling press, I observe that the rollers of the press need only once to be regulated, and that greater or less pressure can be attained by thicker or thinner covering of the print with sheets of paper. This gives much greater security than can be had when constantly readjusting the rollers.{76}

THE FURTHER TREATMENT OF THE TRANSFER.Should we now proceed directly to etch the copy, the acid would act through the drawing, which is as yet but loosely attached to the zinc, and would at last cause the lines to appear broken, if not destroy them.

Should we now proceed directly to etch the copy, the acid would act through the drawing, which is as yet but loosely attached to the zinc, and would at last cause the lines to appear broken, if not destroy them.

It is, therefore, necessary to replace the loose copy by a possibly dense etching varnish, attached fast to the zinc, and to produce an intimate connection between the latter and the etching varnish. Here we meet a difference between the French and Austrian methods. The former, totally based on the lithographic process, favors the use of a resinous dense color as astrengthening material, whereas the Austrian method employs an ordinary copying color and endeavors to form an etching varnish by sprinkling and melting in a quantity of finely pulverized resin. In the method of etching with copper sulphate, it was attempted to restrict the corroding action of the sulphuric acid by the following method: The drawing, rubbed with color and thinly besprinkled with resin, was slightly melted in, then sprinkled and rubbed with the finest silver graphite or real water-gold. It was thus made an electric conductor. A thin coating of copper was then deposited on the drawing, which, in point of fact, hindered the destruction of the film. At the same time, however, the process became uncontrollable, since often a deposit of amorphous copper became tightly fastened to the metallic surface. The lateral action could not well be ascertained, since the narrowest parts were often clogged with metal, without preventing corrosion from below.

The French method of etching is this: A thick solution of gum-arabic is mixed with extract of nutgalls; this is carefully spread over the surface of the plate by means of a fine sponge, and dried by a fan. Then a knife’s point full of etching color (composed of 500 grammes chalk color, 40 grammes coagulated mutton suet, 40 grammes soap, 125 grammes yellow wax, 40 grammes margarin, and 40 grammes oleine, melted in the warm bath and passed through the color mill) is dissolved in oil of turpentine, and a portion of this solution is spread uniformly on the grinding stone by means of a fine sponge, so that the latter contains a similar layer of color throughout. The fatty gum film is then washed, with a wet sponge, free from fat and acid; a fresh quantity of the gum and nutgall solution is poured out, and the copy is by degrees strengthened by rubbing on the etching color with a sponge. This is repeated until the drawing has attained the proper strength throughout. The superposed layer of gum is then washed off, the superfluous water is removed with a sponge, a wet cloth, and blotting-paper, dried with a fan, then gently warmed.{77}

Now the plate is to be dusted with the finest pulverized resin, consisting of equal parts of Syrian asphalt, washed in alcohol, and of mastic; the superfluous resin is removed with a brush and some cotton; the plate is then carefully heated, without beginning to melt the resin, however.

This, by the French method, finishes the plate for etching. Only weak acid is safe for such a plate, however.

According to the Austrian method (practised by me for several years), we proceed as follows: The copied plate is first copiously coated with a cold saturated solution of gallic acid, and then with a pure solution of gum. Without allowing it to dry, I remove the superfluous preparing materials with a wet sponge, and pour on some fresh gallic acid, as with an excess of acid the drawing assumes a more brilliant black color.

The strengthening with ordinary copying color I effect, as the case may be, with the rollers, the sponge, or by coating.

(a)Strengthening with the Rollers.—I roll out some thick copying ink with good, rough rollers which have been frequently used, and begin to roll the transfer plate while still damp, without any pressure, till its surface begins to dry. I then grasp the handles of the rollers more firmly and blacken the dry plate uniformly, giving it a thin coat of ink. This done, I moisten it a little and roll it regularly with rollers freshly treated with color, so that the picture comes up harmoniously and strongly.

Rolling off during drying keeps the gum solution from the drawing while drying on, and keeps open the connection for rolling in.

Before going further I will explain the terms used*: To roll in is to give color or ink, and is done slowly, with tightly grasped handles and certain pressure. Rolling off is effected with loosely grasped handles, without pressure, and quickly, and is intended to draw off with the rollers any excess of color on the plate.To work outormake the rollersmeans to bring fresh color on it from the grinding stone, and is done with strong pressure and strong traction. The correct management of the rollers rests in the wrists. Toreverse the rollers, tochange the handles, means to turn the rollers around, to make the left-hand handle the right-hand one, and thus to correct irregularities in the distribution of color. After every advance and return on the stone or plate to be blackened the rollers are newly adjusted. The plate thus strengthened must be well{78}washed with clear water, to be dried, and at times even to be retouched with a brush and color dissolved in oil of turpentine.

* Color and ink are synonymous. “Burn in” and “melt in” mean the same.

(b)Blackening inwith a sponge. The initiatory etching is done with gallic acid, the gum coating put on and additional gallic acid poured over; then some turpentine solution of copy color, the consistency of syrup, is rubbed over the plate until the picture is uniformly strengthened. If, as may happen in hand-drawings, the color should become massed and not attach itself smoothly, it must be washed off with turpentine and then clean color must be rubbed on.

This operation requires great delicacy. After having finished the blackening in, rinse well, dry with a sponge and thick blotting paper. Heat, so as to vaporize the last remnants of dampness, and retouch.

(c) A peculiar method of strengthening, nowhere described, as far as I know, is that of drying the plate after coating it with gum, then washing the gum with water; then, after drying, of covering the plate with a thin solution of wax, asphaltum, rosin, and shellac in ether, and of carefully coating the quickly drying film with gum. The film remains on the lines of the copy, but easily detaches itself from the bright metallic spaces, which have an insoluble combination with the gallic acid and gum, and are thus protected from the fat.

Faults in strengtheningare caused by the following:

a.By ink which is too thick or too thin, or which has not been well ground. Stripes are caused by the dissolving of the color which is already present.

b.By excessive dampness on the plate (it does not take the color; the color in the sponge changes to a slimy emulsion).

c.By too great pressure with the color sponge the fine parts are lost. The same is the case with careless washing of the color of hand-drawings.

d.Inrolling onexcessive moisture on the plate spoils the work. The surface of the rollers becomes glossy and must be again inked.

e.In pouring out the ink a very thick layer prevents the strengthening of the finest lines.

Dirt on the plate often comes from handling the drawings; it must be scratched off and the plate must be perfect before proceeding.

Now comes the changing of the ink into an etching varnish. But before beginning we must cover the free edges of the zinc for the distance of half a centimetre around the drawing with a solution of ink in turpentine; the same applies to large white surfaces in the drawing, which it is more convenient to cut out with a scroll saw. Then subject the plate to the finest asphaltum{79}powder, passed through a hair-sieve, and cover it by the dusting brush copiously with powdered rosin. Continue the rubbing on of fresh powder for a minute, until the ink is saturated, then dust out the superfluous powder with the dusting brush and fine cotton, so that the metal is bright (no film should be perceptible on looking over it).

The plate should now be heated to about 60° C., till the color of the asphaltum changes from a coffee tint to a dead (matt) black. Place the plate in this condition a second time with the asphaltum, which is again absorbed rapidly. Dust off carefully as before and burn in again till the color changes to a somewhat shiny black; the yellow tint must be avoided, because this degree of burning exposes the lights in the closest hatchings to the danger of running together.

Thus the coat of color is changed into an etching varnish of excellent resistance and adhesion, and the plate is ready for etching.

THE ETCHING AND ITS INTERMEDIATE TREATMENT BEFORE MOUNTING THE CLICHÉ.Introductory remarks.—If we examine a wood cut or an electrotype with regard to the depth of its narrow and wide-line complexes, we can at once determine a plane for the closest hatchings; in a uniformly deep layer the lines lie at a moderate distance apart, and those of the highest lights are very deep. These three planes are situated higher or lower according to the very narrow or very wide series of lines. This gives a natural division of the different stages of etching, and, according to the three depths, we distinguish thesharp etchingoretching onin which the engraving must advance far enough to place the narrowest portions sufficiently low;middle etching, which has to accomplish the same for the moderately narrow portions, anddeep etching, which must attain sufficient depth for the highest lights.

Introductory remarks.—If we examine a wood cut or an electrotype with regard to the depth of its narrow and wide-line complexes, we can at once determine a plane for the closest hatchings; in a uniformly deep layer the lines lie at a moderate distance apart, and those of the highest lights are very deep. These three planes are situated higher or lower according to the very narrow or very wide series of lines. This gives a natural division of the different stages of etching, and, according to the three depths, we distinguish thesharp etchingoretching onin which the engraving must advance far enough to place the narrowest portions sufficiently low;middle etching, which has to accomplish the same for the moderately narrow portions, anddeep etching, which must attain sufficient depth for the highest lights.

On account of the lateral action of the acid it is impossible to etch down perpendicularly, but a wider covering is taken for each stage. Of these wider coverings there remain after etching all around the relief two terrace like grades, which must also be removed.

We have, then, in addition to the above, three sorts of etching, around etching, in which the grade remaining from the deep etching is to be removed, and aclean etching, or a removal of the wire-edge left after middle etching.

This natural subdivision is found in the old French method as well as in the{80}new method, and both coating and the acids are of a strength proportionate to the different stages of the work.

We have already alluded to the lateral action of the acid; it is a factor that taxes the care of the etcher in the highest degree. In the beginning of the action of the acid, the edge of the metal under the coating is exposed the more, the longer the action lasts; here, of course, the dissolving power becomes apparent. The deeper we go, the more the metal under the line is exposed, and the action on the lateral edge continually increases. In the effect of the acid we distinguish thence, a perpendicular and a lateral action. Since the latter cannot be removed by changing the character of the acid, we must give it a part in this process of dissolving metals, but at the same time must invent a method which will prevent the lines from growing thin.

But in order to do this we must know the relation of the perpendicular to side action. Both are in proportion, a result both of theoretical and practical consideration. In order then to attain a certain depth of etching, a proportional lateral protection must take place, which is by degrees destroyed by the lateral action. Since this lateral action sets in at the beginning of the work, the dimension of the line must be secured from the start. This is done in the Vienna method by the already mentioned formation of the etching varnish, by means of dusting with resin and burning in, by which an almost imperceptible growing of the width of line is attained. The French method endeavors to correct this by using a very weak acid and a correspondingly thin coating, but coating oftener and etching at every new coating, as we shall see below. Also the coating for middle and deep etching must be arranged in accordance with the principles above elucidated. As deep as the middle or deep etching is desired, so wide must the lines be surrounded by etching varnish.

ETCHING BY THE FRENCH METHOD.We have already seen (p.76) how a copy is made by the French method for etching, and we now continue the development of this process.

We have already seen (p.76) how a copy is made by the French method for etching, and we now continue the development of this process.

Into a tray pour 4 litres of water at 18° C., add 15 c.cm. nitric acid and mix well by shaking. Then place the prepared plate into the bath and rock it for seven or ten minutes (according to the fineness of the drawing), rinse well with water, remove the remaining water with blotting paper, and, finally, dry thoroughly with a fan. (Do not forget to dry the back.) Now warm the plate from the back, moving the flame about continually, so as to secure uniform heating and prevent warping of the zinc. The asphalt powder, which is as{81}yet but loosely attached, is more intimately connected with the subjacent ink through this heating process. The combination becomes evident from the assumption of a black lustre. With the appearance of this, stop heating, and lay the plate on a cold stone to cool. This done, spread some gallic acid over it with a soft sponge, and without washing it off, spread gum on the surface of the plate, and hasten the drying with a fan.

Mix some etching ink with varnish and work it out into a thin layer with good rough rollers. If the rollers are in order, wash the coat of gallic acid and gum from the plate, remove superfluous water androll in(the manner similar to that used in lithography). The surface of the plate should not be more than moderately damp, so that the rollers may not slip. If a coat of color has been uniformly deposited, wash the plate with clean water, remove the excess with a sponge and blotter, dry by fan and remove all moisture by heating to 45° C. Dust the warm plate again with asphaltum (remove the excess), and warm it a trifle to secure better adherence. Strengthen the bath by the addition of 15 c.cm. nitric acid, and etch again for seven or ten minutes under continued shaking. Then rinse the plate, remove the water and dry with a fan, and burn in the resin powder well. Careful inspection will now show a successful and uniform but still weak relief.

As before, the plate is coated with gallic acid and solution of gum, is dried, washed, andblackened in, in which treatment one-third “wax pomatum”* is mixed with the etching ink. After washing and drying heat the plate up to 60° C., thus causing an imperceptible widening of the drawing. After coating dust once more with asphaltum, warm it and cover only the back and the white rim around the drawing with a solution of shellac (1 part ruby shellac in 10 parts spirits). Strengthen the bath with 20 c.cm. of acid and bathe it for seven to ten minutes, shaking the bath regularly. Continue until you see that the lateral action of the acid has almost wholly destroyed the lateral covering produced by heating. Do not, however, etch too long, and do not mistake theover-hanging coat for the other. Then follow washing, drying, melting on some resin, cooling, coating with gum, blacking in with equal parts of etching ink and “wax pomatum,” then washing, drying, greater heating (70° C.) (so that by increasing the ink each line receives lateral protection), cool and dust to excess with the finest resin dust.{82}

* Wax pomatum is prepared by cutting beeswax into fine parts and covering it in a wide-necked flask with oil of turpentine. In a few days a jelly-like mixture will remain, which serves the above purpose.

As we have now reached the necessary depth for the narrowest portions, we use, instead of the asphaltum, resin, which melts easily and spreads out readily, in order to attain protection for our middle etching.

Strengthen the bath with 30 c.cm. acid, and bathe until the lateral action of the acid has reduced the lateral coating to a narrow edge. Then wash, dry, melt on some resin, cool, prepare with gum. Blacken in as before, but employ one-third etching ink and two-thirds wax pomade and apply so thickly that all the narrowest spaces of the drawing are completely filled with color. Continue warming until the ink, which was applied, has well covered each line; then dry and use resin as before.

The acid may now be strengthened by 100–158 c.cm., according to the strength of coating chosen. Bathing must be continued until the edge that has run off begins to grow narrow. Wash, dry, burn in resin, cool, coat with gum, and blacken in by rollers with clean wax. Continue heating until each line is well covered by ink. Always dust until the ink is fully saturated and then heat gently.

Strengthen the bath 200 c.cm. and begin thedeep etching. According to the depth to be attained repeat the manipulation of strengthening once or twice. Whenever a corrosion of the lateral coating becomes apparent, coat freshly, adhering to the above order of operation. For obtaining the necessary depth ink is applied abouttentimes, adding wax each time to facilitate the spreading when warming.

In order to attain a fine, regular lateral coating, great ability in manipulating the rollers is necessary, since without such the correct degree of strengthening is never attained. Irregular coating leads, of course, to irregular melting of the ink; one spot then is already sufficiently wide, while another is not yet covered. In such cases coating with a brush must be resorted to.

If the necessary depth is attained, the plate is to be freed carefully from the coating with a brush and oil of turpentine, and then placed in fresh sawdust, which absorbs the oil of turpentine and leaves behind a clean surface. Now the work can be criticised in all its parts. To every coating is a corresponding narrow edge of etching, which is now to be removed in order to make the plate fit for printing. To removing these edges we must devote our attention. We begin with the top one, and make preparations thus: Roll out on a clean, warm stone with faultlessly smooth rollers a very thin gauze-like layer of etching ink. Likewise warm the zinc plate and roll it in all directions without pressure till the picture becomes beautifully black.{83}

Pressure must not be employed, but the coating must be obtained by renewedworking outof the rollers on thecolor-slab, and repeated coating. When at last the desired strength is obtained, dust with the finest asphaltum powder, blow the traces of dust out of the hollows, and warm till the layer becomes slightly brilliant. Next, etch in a new bath of 4000 c.cm. of water and 40 c.cm. of acid for 7 minutes, wash, and dry well; then, with more ink on the rollers, coat the dried plate, dust once with resin, heat gently, then apply the asphaltum and burn in strongly. Thus the first relief is protected laterally, and the first grade can be etched down completely, without endangering the drawing. To remove the second grade, we repeat washing, and put on etching ink mixed with one-third wax. Rolling must continue till the narrowest spaces of the etching are completely closed. Then follow dusting with resin, warming, and placing the warm plate in the asphalt, dusting, removing the excess, and finally burning in.

With this coating a further rounding of the grades can take place (in a bath of 10° Baumé). Continue this process until all the grades are removed and the etching appears as perfect as a cast plate.

Since hitherto all publications on chemigraphy have duly described this method, I believe that I should not enter into further details, improvements, etc. Suffice it to call attention to weak points. In view of the new method later to be described, the reader may make a comparison between the two.

A very weak point is the method of strengthening based on the lithographic process of superimposing new color upon the old color. In consequence of the repeated melting in of resin, this latter acquires an uneven surface, which can be blackened in only with great difficulty. Equally untrustworthy is the lateral protection bymelting off, which is only attained with safe uniformity by skilled workers. And what is more, with the weak coating at the beginning; even weak acid often works its way through to the etching, so that the finished etching appears slightly porous, and gives no dense black print. Also shaking, which is to promote the removal of the metallic mud and the gas bubbles from the lines of the etching, has an unsatisfactory effect, inasmuch as the single lines are often thus under-washed.

But the principal defect is that no accurate determination of the degree of each operation can be made, everything depending on the delicate execution of the process.

The time that the etching of a correct, deep cliché requires by this method is from eight to ten hours. This procedure also demands better trained hands{84}than the Austrian, which, in large establishments, is based on a division of labor, and in which men trained in a single manipulation, under good supervision, accomplish the maximum work surely and excellently.

Furthermore, the expenses of the manufacture on a large scale are far greater, since each etcher draws a greater salary than a workman skilled in a few manipulations, such as the following method requires.

THE AUSTRIAN METHOD—THE ETCHING ON.I have already shown how a transferred plate should be prepared for etching by this method. Before proceeding to the details, however, we will prepare the etching baths, which, by the way, may always be employed for several plates. Corresponding to the three steps of etching, we require three baths of different concentration to be determined by means of an areometer with a Baumé scale. The bath foretching onis prepared in strength of 2° Baumé at a temperature of 18° C. There must be a quantity sufficient to cover the plate to a depth of 4 to 5 centimetres. The bath for middle etching requires 10° Baumé and a temperature of 18° C.; the bath for deep etching, 18° Baumé. These baths are prepared at the beginning, and are used for the five successive stages of etching. If, after continued use, the bath for deep etching should grow weak, it may be used for middle etching. For protecting the trays, I recommend a coat of gutta-percha over a well-coated inner surface of asphaltum. Everything being ready, immerse the prepared plate in the bath, and with an etching-brush brush the surface of the plate uniformly for two minutes.

I have already shown how a transferred plate should be prepared for etching by this method. Before proceeding to the details, however, we will prepare the etching baths, which, by the way, may always be employed for several plates. Corresponding to the three steps of etching, we require three baths of different concentration to be determined by means of an areometer with a Baumé scale. The bath foretching onis prepared in strength of 2° Baumé at a temperature of 18° C. There must be a quantity sufficient to cover the plate to a depth of 4 to 5 centimetres. The bath for middle etching requires 10° Baumé and a temperature of 18° C.; the bath for deep etching, 18° Baumé. These baths are prepared at the beginning, and are used for the five successive stages of etching. If, after continued use, the bath for deep etching should grow weak, it may be used for middle etching. For protecting the trays, I recommend a coat of gutta-percha over a well-coated inner surface of asphaltum. Everything being ready, immerse the prepared plate in the bath, and with an etching-brush brush the surface of the plate uniformly for two minutes.

The hairs of the brush must only rest lightly on the metallic surface. For determining time, use sand-glasses of two, three, and five minutes. After two minutes, take the plate out of the acid, wash it well with water, and examine it carefully. If the effect has not been uniform, see that two minutes more can be safely given in the etching bath. If by any sort of careless handling the plate has been injured, dry it with blotting-paper, vaporize the remaining dampness, and cover the soiled spot with very thick solution of asphaltum in turpentine. Cool, and continue brushing lightly for two minutes in the bath.

At the end of this time, wash and examine again. Even now everything will be intact. With very fine drawings, however, lateral action has already progressed so far that, under all circumstances, the exposed edges must be covered. Coarser drawings generally stand one or two minutes more.

To try the depth of etching: with your finger-nail on the edge of the black{85}rim, feel how far the etching-on has proceeded. As soon as the finger-nail catches, the depth is sufficient, and the sides of the lines may be covered.

For this operation the plate needs, above all, thorough washing, drying on both sides by blotting-paper and gentle heat, and a temperature of 45° C. At this temperature place the plate into the finest resin-powder, and rub the latter several times over the warm drawing, using for this purpose a fine brush. The protection, which has grown sticky through heating, retains a thin coating of resin, which, after dusting off the bright metallic spots with a brush and fine cotton, and after careful fanning off, is reheated to about 50° C. At this temperature the plate is returned to the white rosin, receives a good dusting-in, and being freed from excess as before, is heated to about 65°, so that the easily fusible rosin begins to spread out. At this moment extinguish the light, and put the plate into the asphaltum, which will attach itself copiously to the sticky resin. Brush the plate well with the substance, remove any excess from the bright spots, heat to 80° C.; then place it again into the asphaltum, brush it, clean it by removing any excess, and heat it to 100° C., when a complete combination of the resinous mass takes place, and a uniform etching varnish is formed. This last coating is extremely regular, and it is wonderful to see the accuracy with which the lines have been covered. Beginners are warned to pay attention to the careful cleaning of the bright parts of the plate when brushing and dusting it; should any resin remain behind, it melts on, and grows by degrees to a strong yellow tint, which is very difficult to remove, but very easy to guard against. Never forget to dust off the back.

While the plate is still hot, lean it against the wall, face in, and the back covered with a solution of shellac.

Now the plate is ready for further etching, which is carried on for two minutes in the first bath. At the end of two minutes, wash and examine critically. In almost every case we may etch for a third, or even a fourth time. It is, however, sufficient for the beginner to know that he has sufficiently etched in two spaces of two minutes each, after preparing with resin. Trying and examining with the finger-nail on the black edge will show a fine relief. Should it be possible to etch for a third space of two minutes, or even of one, without danger, it is preferable to do so. It should be a rule to proceed as far as possible, judging from the character of drawing and coating. Experience is easily gained in two or three trials, since anything can be examined at any moment. Beginners would do well to use a magnifying-glass with good field of view in examining, when they can observe the most sensitive portion, and{86}all changes may easily be noticed. The brush should be used lightly, to prevent scratching. Usually, it is fastened at right angles to a stick to protect the hands from the effect of the acid.

To raise the plates out of the tray, lay a gutta-percha thread into the bottom of each tray, fastened at one end to the top edge of the tray, projecting over the same on the other side. The plate is placed on the thread while etching. It may be removed without touching the bath by pulling the free end of the thread.

As already remarked, the spreading of ink on a surface which is more or less rough is difficult. For this reason the plate, when etched-on after my method, is to be washed out with oil of turpentine. A strong brush should be used for this, and some of the oil rubbed over the plate without pressure. You must cause a dissolving, not a rubbing off, of the coat. On continuing the addition of turpentine, the metal grows bright. Take, then, a handful of the coarsest of pine-wood sawdust and rub off the surface. This removes instantly every trace of turpentine, leaving a clean surface behind. For the sake of security, pour on more turpentine, rub with a somewhat softer brush, and remove again with clean sawdust.

It is important that the wash-table should always remain free from sawdust, which latter should fall through the grating into a suitable receptacle. If this rule is disregarded, the wash-brush will soon be a conglomerate of sawdust and hairs. Sawdust and turpentine will stick to the brush so tightly that a new brush will have to be purchased.

Now we again examine our work. It is a mark of success if the relief still shows its original smoothness in all its parts, and has nowhere grown porous. All the parts must be clear in their correct proportional strength, as seen in the transfer.

The treatment of the plate from the time of transfer to the close of the etching-on takes: for the saving of the edges and the white portions of the drawing, 2 minutes; for preparing twice with asphaltum, 4 minutes; for varnishing the back and coloring the plate, 4 minutes; for etching-on the lateral protection, 4 to 5 minutes; for preparing twice with resin, asphaltum, and varnishing, 16 minutes; for renewed etching, 4 to 5 minutes; and for washing, 5 minutes—that is, 33 minutes in all. Add 7 minutes for inspection and retouching, and 40 minutes will be the space allowed for etching-on.{87}

MIDDLE ETCHING.In order to give to the middle tints of the drawing the depth necessary for printing, we begin with a new blacking-in. We need for this purpose excellent, smooth, and hard rollers, which are immersed in minium and linseed oil, and are then left to dry for a short time. Contrary to the French method, we need here a thin composition for the etching ink, obtained by concocting equal parts of paraffine, suet, beeswax, and ordinary ink, prepared in an excess of good linseed oil. (Ready-made color of right composition may be had of E. Liesegang, in Dusseldorf, and other dealers.)

In order to give to the middle tints of the drawing the depth necessary for printing, we begin with a new blacking-in. We need for this purpose excellent, smooth, and hard rollers, which are immersed in minium and linseed oil, and are then left to dry for a short time. Contrary to the French method, we need here a thin composition for the etching ink, obtained by concocting equal parts of paraffine, suet, beeswax, and ordinary ink, prepared in an excess of good linseed oil. (Ready-made color of right composition may be had of E. Liesegang, in Dusseldorf, and other dealers.)

This color, when of right composition, possesses the power of absorbing resin-powder, and changes in combination with the same, when heated, to a compact, very solid, yet brittle mass.

Of this color, which is soft as butter, take a portion on a knife-point, and spread it upon the smooth rollers, forming a perfectly uniform layer. The complete covering is done by rolling, changing the adjustment at intervals. When a perfectly uniform, oily coat is spread on the color-slab and the rollers, begin rolling-in the washed plate.

Do not exert any pressure, but roll, carrying the handles so as to black the relief only from the surface of the rollers. Of course, it cannot be prevented, and is of no consequence, if ink attaches itself to the large white spots. Rolling continues till the oily brown coating has deposited itself uniformly. Exercise care in order not to get more ink on some spots than on others. The plate, now completely rolled, is placed in the finely powdered resin, with which it must be completely covered. For the space of two minutes the oily color absorbs the powder, which should, therefore, be strewn on it and rubbed off repeatedly. If saturation in the cold has taken place, dust off lightly with brush and cotton, blow off well, and heat uniformly to 35° C. The resin should not melt now, but should only grow sticky and combine intimately with the color, which forms the binding material. This change is observed immediately in the change resulting in the gray resin coat. As soon as the change occurs (beware of unequal heating), again place the warm plate into the resin, saturate as before, dust out, blow strongly on the bright, metallic spaces, to remove remaining traces of resin, and heat to 50°–55° C. At this temperature cover the film with fine asphalt powder, dust off as before, and heat to 65° or 70° C. In this condition the plate is again saturated with asphalt, and the layer, after careful dusting and blowing, is heated until it grows slightly{88}brilliant. Thus a complete coating is formed, and the plate has the appearance of Fig. 6. The black spots represent the dirt which has clung to the intensest lights, and must be removed. But before attempting this, we varnish the back of our plate with a solution of shellac, and cool it completely in water.

Fig. 6.

Now take a very coarse scraper, ground with a sharp edge; hold it between the index and middle fingers, and scratch away the dirt from the light spots, making the edge of the scratcher draw the strokes close together. The brittle backing breaks off finely, and in a few minutes the dirt is removed and the plate is ready for etching. If (which will only happen to beginners) the drawing should be scratched, the exposed spot must be covered, by means of a brush, with a thick, warm solution of asphalt in turpentine; the dirt which was scratched loose is brushed off, and the plate goes into the bath for middle etching for about three minutes. Brushing and washing follow in the same way as in the previous operation. At the expiration of three minutes inspect (with or without a magnifying glass); places that have been uncovered must instantly be covered with asphaltum, as already directed. Etching is continued till the lateral coating no longer protects the first relief, which generally takes place after the third period (in about nine minutes) in a new bath, but requires twelve to fifteen minutes in an old one. It is proved by the existence of only a narrow thread alongside of the relief. The moment can be well ascertained. If we wish to be sure of it we may do so by exposing the edge of the black rim at different places; the width of the thread is then apparent, and a safe conclusion may be drawn from the single spots as to the whole plate. If not enough middle etching has taken place, the thread remains wide and requires an extraordinary clean etching, which may lead to the picture growing thin and endanger the finest lines. Care, then, is necessary to ascertain the right moment of suspending the middle etching, and of continuing in the above-described manner with oil of turpentine, brushing, sawdusting, and washing. After drying and brushing off the sawdust with a strong brush, we have the clean plate ready for examination. We observe the grade of etching produced by{89}middle etching parallel to the contours of the different parts, and can safely assert that the process has taken its natural course. Etchings without real deep places (as high lights) might here beetched clean—that is, might undergo removal of the formedetching grade. Yet it is preferable to place the edge of the drawing as low as possible, to prevent a tendency to crookedness, so-called facetting, and to get a deep edge for nailing the plate on wood. The outward appearance of the etching improves considerably, and the cliché can be fastened much more securely. The chemigraphist must endeavor to satisfy the demands of the printer in all respects, and should omit nothing that serves to perfect his work. Thus only can he gain a good reputation both for himself and for his work.

DEEP ETCHING.Having been successfully treated in the middle etching process, the plate needs only depression of the larger light spots. Some simplify this part of the work by cutting out the highest lights by means of a chisel, reverse ground. This can easily be done after a little practice, and often saves time and acid. Care should be taken with the chisel; the plate should lie on a flat surface and the cutting twist be executed lightly and regularly. If this course is decided upon and is applied to the highest lights, proceed to the execution of the deep etching. Such chiselling does not happen in my laboratory, since I prefer to etch all plates alike to their normal depth.

Having been successfully treated in the middle etching process, the plate needs only depression of the larger light spots. Some simplify this part of the work by cutting out the highest lights by means of a chisel, reverse ground. This can easily be done after a little practice, and often saves time and acid. Care should be taken with the chisel; the plate should lie on a flat surface and the cutting twist be executed lightly and regularly. If this course is decided upon and is applied to the highest lights, proceed to the execution of the deep etching. Such chiselling does not happen in my laboratory, since I prefer to etch all plates alike to their normal depth.

An excess of ink is now well spread over the rollers and the plate is rolled in all directions. Close up all the middle tints and give the acid room only in the densest lights. This coating is done by warming the regularly covered plate to 31° C., and allowing the ink to flow down rapidly and cover the recesses. A second coating with slow manipulating of the rollers and manipulation of the handles without pressure, will yield a sufficient coat from above. If, despite this, certain parts should not be sufficiently blackened, rub on more ink till the covering is sufficient and the side protection perfect.

As in middle etching, we must proceed to the formation of an etching varnish by dusting with gums, placing into resin, by lightly rubbing this resin on in constantly renewed layers, till the absorptive power of the ink ceases; then warming and dusting warm with the same resin to complete saturation; then raising the heat as above, and dusting with asphaltum to saturation, heating stronger and finally placing the hot plate into asphaltum, which again secures all parts covered with ink and resin.{90}

At the different times of removing the dust, pay particular attention to the bright metallic parts. Over-removal of dust removes resin from the layer; under-removal leaves behind an obstinate yellow tint in the bright spots. Practice and experience readily prove the best teachers in this respect.

The final heating of the etching varnish must be pushed so far that an intimate connection is effected between all of its parts. This is easily noticeable from the uniform gloss of the mass. While still hot, the back of the plate is carefully varnished and cooling is promoted by dipping it into cold water.

Fig. 7.

But few spots are to be removed by chiselling (see Fig. 7), for the rollers have only blacked the middle of the highest lights. These spots, as indicated in middle etching, are scratched bright with a chisel. It is important always to scrape off the white edge around the drawing. Scratching of the plate does not even happen with beginners, except in cases of gross carelessness. If it does happen, a good covering with the turpentine solution of asphalt must be used. When this is all done properly we proceed to etch.

The process of etching by the aid of a brush is continued in periods of five minutes each. It is necessary to examine the side covering carefully at the end of every operation; a diligent brushing off of the surface is also to be recommended. Etching is continued until, by degrees, the lateral coating decreases and the grade grows narrower. At this juncture—that is, after about five to six operations (twenty-five minutes) the necessary depth is attained. In few cases (and almost always with beginners), it happens that a single coating does not suffice for deep etching without endangering the plate. In such cases wash the plate, coat it a second time, and form a second etching varnish.

When the depth is satisfactory the plate is washed and the new grade may be criticised.

After a proper examination, we proceed to the

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