The Invention of Lithography Part 15

(1) Limestone has countless little pores. These can soak up fatty as well as watery substances.

(2) These can adhere easily to the limestone particles, but are easily separated again, as long as the nature of the stone is not altered. This alteration is produced most readily by sulphuric acid, tartaric acid and phosphoric acid.

(3) Water evaporates from the pores as the stone dries. Gum and other slimy substances do not.

(4) Fats soak into the stone more and more. There is no means of destroying them except to remove the limestone itself by grinding or etching.

(5) Printing-color cannot adhere to the stone so long as a proper amount of moisture forms a wall between it and the stone. Under any circ.u.mstances it adheres only poorly to the lime particles, and a.s.sumes great power of adherence only when the pores of the stone are filled with fat, which are pinched in them, so to speak, and with which the printing-color strives to unite because of mutual affinity.

(6) This stronger adherence (or complete color reception) thus happens only when the outer color can reach and touch the inner fat. If the latter is deep in the stone, so that the communication is broken, it becomes difficult and the communication must be restored.

(7) This interruption occurs either if the color is rubbed away by force and with help of moisture, or if a substance that closes the pores unites with the stone.

(8) The rougher, sharper, and more angular the pores are, the more readily does the color find adhering points. It adheres at first to the surface by virtue of merely mechanical conditions. But when the moisture which hinders a complete union and greater penetration has dried, the color begins to penetrate deeper into the stone and to fill its pores.

The most color will always adhere to rough spots. Therefore, it happens often, in some styles of work, that a stone too highly polished will seem perfectly black when inked, and still fail to yield a strong impression. For the same reason the impressions from soft stones usually are the stronger, especially if the mode of printing demands the use of thin printing-color.

(9) The effect of the etching fluid is in part a greater polishing of the surface, in part a filling of pores. Both make the stone reluctant to take color.

(10) If the stone has been prepared and polished already, it can be made rough again and receptive to color by being reetched. At the same time the prepared surface can be destroyed by etching, and a communication established with the fat lying in the interior. The result is according to the manipulation.

So much in general. In describing the various styles I will make everything clearer.

CHAPTER IV

THE NECESSARY TOOLS AND APPLIANCES

In lithography there is use for many various tools and utensils. I will mention here merely those that are made primarily and exclusively for the art.

I

CONCERNING STEEL PENS

One of the most necessary tools of lithography is the steel pen for writing and drawing on the stone. Simple as its manufacture is in principle, it demands much care and skill. The beauty of the work depends largely on a good and well-cut pen. The best artist, using the best chemical ink on a perfectly prepared plate, cannot do good work unless the pen is good and cut to suit his hand. Therefore it is necessary to learn how to make these pens, because, apart from their costliness, it is difficult to get a suitable one from a worker in steel. The ordinary steel pens that can be bought ready-made from stationers are fairly available for coa.r.s.er writing and drawing; but for better work one must have much finer pens.

Following is the way to make them:--

Take the spring of a pocket watch, not too small nor too broad; one and a half to two lines in breadth is best. Clean off all fat by polishing with sand or chalk. Lay it in a gla.s.s or porcelain vessel, and cover it with a solution of aquafortis and water in equal parts. Let the acid etch the steel till it has lost about three fourths of its thickness, and has become as pliable as a similar strip of letter-paper. From time to time the steel must be removed from the fluid and dried with tissue paper. This produces uniformity of etching. The steel rarely is quite uniform, and it has happened to me often that it is attacked unequally and that holes are eaten into it before it has been etched away sufficiently. That this, however, is due mainly to the quality of the acid, I learned because I found that the same steel would be attacked clean and uniformly as soon as I obtained aquafortis from some other source.

A pen is poorly etched if it has many elevated points or pits and holes.

The former appears to result from insufficient cleansing, the latter is due to the quality of the acid.

Oil of vitriol diluted with water, or nitric acid can be used.

Those who have a very light touch may etch their pens to great thinness, and will be enabled to do very delicate work. For a heavy touch they must be firmer, otherwise fine strokes will look shaky.

When the steel is thin enough, it is removed and cleansed with fine sand that it may not become rusty in future. Then it is cut into pieces two inches long with good English shears. Now these must be shaped half-round. To do this, lay them on a flat stone and beat them lengthwise till they bend, using a small watchmaker's hammer, whose faces are pretty thin but well rounded. Two or three sheets of paper laid under the steel facilitate the work.

Another way to give it the half-round form is to file a groove into a stone, giving it the exact shape the pen is to have. Into this groove lay the piece of steel, put in a drop of vegetable oil, and polish with a steel instrument whose end resembles a broken but well-rounded nail.

Use sufficient pressure, and the steel will gradually a.s.sume the desired shape.

Either of these methods may be used, according to preference. It is to be noted that the degree of roundness depends on the artist's need, one finding a well-rounded pen better, another preferring one not so well-rounded. The less the pen is rounded, the more it will resemble a brush when used, but the points will not spread so well without considerable pressure. The more they are hollowed, the stiffer are the pens and the more easily will the points spread when pressed.

After the pen is curved, it must be cut. With small, well-sharpened scissors cut a slit about one line in length into one end. Then cut away from the two sides as much as necessary till the point is sufficiently fine. Do not cut away too much at once, as the pen bends easily and then must be straightened out again, which demands especial skill. It is well to do the cutting from the point toward the sides.

A good pen must have both points very uniform, so that they touch perfectly and lie on the stone evenly in the position given them by the hand when working. The cutting alone will do this, but a small, very fine whetstone may be used to aid.

A newly cut pen is somewhat rough at times and cuts into the stone, thus gathering powder that hinders the work. This defect generally cures itself after a few strokes on the stone. Beginners generally spoil their pens by bending them every few moments. Then they must be straightened out, which demands practice and judgment. It cannot be described, because the bending may a.s.sume a thousand shapes. It may be mentioned, however, that the points must always touch, but must under no circ.u.mstances interfere, one being forced behind the other. It is good, sometimes, if one can see through the slit when looking backward from the point. Some even cut a tiny bit out of the middle for this purpose, but that demands great skill and extremely good scissors, as otherwise the opening will be too large, which will spoil the pen entirely.

The ordinary drawing-pens, which can be loosened or tightened with screws, can be used very readily for drawing lines, if their points are made from very good steel that can be ground very fine and thin.

However, for much line-work, for instance the background of a picture which consists of lines hatched crosswise, it is better to use the other pens. The ordinary drawing-pens are too likely to catch a little dust or dirt between their points, and then will spoil the lines.

Of all work of the pen style in lithography, the most difficult is to draw very fine and even lines with a ruler. I have succeeded best by using a pen previously so cut or ground that both points touched in the position in which I was accustomed to hold the pen when guiding it with the ruler. It is evident that the pen must be held to the ruler on its side, so that the groove that contains the ink does not point in the direction of the ruler, but away from it. It is well if there is a tiny s.p.a.ce in the slit, as it helps the free supply of ink.

II

CONCERNING BRUSHES

Brushes are used for various purposes, as to prepare the plates, cleanse, etch, etc. Here, however, we speak chiefly of the small brushes required for writing and designing. For this are used the very smallest and best miniature brushes, and they must be especially treated.

If it is desired that the brush make thicker strokes under pressure, the ordinary condition of it, in which all the bristles come to a point, is quite sufficient. But it is very difficult to lay on strokes of uniform thickness with them. Press the brush on the table, spread the bristles fanwise with a knife and cut away from each side about a half-line deep.

Turn the pencil to the other side, stroke it again to spread it, and cut the same amount as before from each side. Continue this till there remain only ten or twelve bristles of the original length in the brush.

Then cut these even at the ends. These should not be altogether the middle ones if the pencil is to be first-cla.s.s. Neither should they be too far apart. They should hang together well when the brush is dipped into the ink, but not so closely that they will not let the ink pa.s.s well. With a brush successfully trimmed thus, the handsomest drawings, resembling copper plate, can be done with ease.

For coa.r.s.er strokes, coa.r.s.er brushes are needed. More bristles are permitted to remain in them.

III

CONCERNING ENGRAVING NEEDLES

These serve for the intaglio process, to draw into the stone, and must be of the best and hardest steel. In Munich there are also used the little five-angled watchmakers' borers, which are glued between two pieces of wood planed round in form of a pencil and so cut at the end that only a bit of the tool is visible. In using very thin needles one has the advantage that they are ground and sharpened easily.

For coa.r.s.er strokes, coa.r.s.er needles are needed. For fine strokes, especially if they are to go in all directions, the needles are best ground perfectly round.

IV

CONCERNING THE DRAWING-MACHINE

To transfer drawings very accurately and reversed on the stone, which is necessary especially in the case of charts and plans, a pantograph is used in Munich, which is so arranged that the stone is upside down and elevated. The inscribing-needle is just opposite the one that is managed by the hand, and when one follows the lines of the original exactly, there results a perfect but reversed copy on the stone. Such drawing-machines can be obtained from Herr Liebherr and Company in Munich. This skilled mechanician also makes a sort of pantograph of his own invention, with which drawings can be transferred to stone, reversed or otherwise, and in any desired proportion. Pictures of such machines may be obtained from him.

V