LITHOGRAPHY.

Lithography is the art of taking impressions from drawings or writings made on stone.

The principles upon which this art is founded are, Hi, The quality which a compact granular limestone has of imbibing grease or moisture; and, 2dly, The decided antipathy of grease and water for each other.

A drawing being made upon the stone with an ink or crayon of a greasy composition, is washed over with water, which sinks into all the parts of the stone not defended by the drawing. A cylindrical roller, charged with printing-ink, is then passed all over the stone, and the drawing receives the ink, whilst the water defends the other parts of the stone from it on account of its greasy nature.

This process, therefore, depends entirely upon chemical principles, and is thus distinct from letter-press or copperplate printing, which are altogether mechanical. On this account it has in Germany been called chemical printing ; and, as metallic plates can be prepared to be printed from in a similar manner, lithography is considered only as a branch of chemical printing.

I. HISTORY OF LITHOGRAPHY.

The invention of lithography was the result of accident. Its inventor, Alois Senefelder, the son of a performer at the theatre-royal of Munich, was placed for education at the university of Ingolstadt, as a student of jurisprudence; but after his father’s death he attempted a theatrical career. Not succeeding in this, he became an author, though his poverty prevented him from publishing his works. He now tried many plans with copperplates and compositions, as substitutes for letter-press, in order to be his own printer. He found, in the course of his experiments, that a composition of soap, wax, and lamp-black, formed a good material for writing on his plates; that, when dry, it became firm and solid, and that it resisted aquafortis. Wanting facility in writing backwards on the plates, he got some pieces of Kilheim stone, as cheap materials, upon which he could practise after polishing their surfaces. One day being desired by his mother to take an account of some linen about to be sent to be washed, and having no paper at hand, he wrote· the account on a polished stone, with his composition ink, intending to copy it at his leisure. When he was afterwards about to efface this writing, it occurred to him that he might obtain impressions from it; and, having eaten away the stone with acid for about the hundredth of an inch, he found that he could charge the lines with printing ink, and take successive impressions. This new mode of printing appeared to him very important, and he persevered through all difficulties in applying his discovery to practical purposes, and in improving it.

In the course of many experiments, he found that it [7:13:381]was not necessary to have the letters raised above the surface of the stone, but that the chemical principles by which grease and water are kept from uniting, were alone sufficient for his purpose. This point obtained, lithography may be said to have been fully discovered. All that was required was the improvement of the materials, and the mode of working with them, and the construction of a proper press for taking the impressions.

The perseverance with which he followed up his experiments, in order to overcome the difficulties which successively arose in his progress, is astonishing, and the more so, considering the total want of method in his proceedings. Often did he waste months in surmounting a difficulty which a little knowledge, or a very little reasoning, would have enabled him to conquer immediately. His uniform plan seems to have been, to try the first thing that came to hand, and so on in succession, till chance rewarded his assiduity by presenting to him the material suited to his purpose.

The first essays he made to print for publication were some pieces of music, executed in 1796; but afterwards he attempted drawings and writings. The difficulty he had in writing backwards led him to the process of transfer ; and the use of dry soap, which was found to leave permanent traces that would give impressions, naturally led to the mode of chalk drawings.

Having made considerable improvements, Mr Senefelder obtained, in 1799, a patent privilege for Bavaria, when he made known his process, and afterwards entered into partnership with Mr André of Offenbach, who proposed to establish presses, and take out patents at London, Paris, and Vienna. For this purpose Senefelder came to London with a brother of André’s, and the invention having been much spoken of, under the name of Poly autography, most of the principal English artists made trials of it. Unfortunately, however, the art of printing from the stones was not then fully understood, and the difference between the materials of Germany and those of England, used both for the purposes of drawing and printing, caused constant failures, and the artists in succession abandoned the practice of it. To this cause is to be attributed the slow progress which lithography made for many years in England, as it was left entirely in the hands of amateurs, whose productions, generally speaking, did no credit to the art, and whose faults .were in some degree supposed to be those of the art itself.

In August 1800, Senefelder, who had now separated from André, went to Vienna, where, after much difficulty, a patent was obtained, and extensive preparations were made, for applying his process to print cottons; but bad management, and some unfortunate circumstances, prevented his success, and he returned to Munich in 1806, leaving the establishment in other hands.

In 1806, Mr Mitterer, professor of drawing at the public school at Munich, practised lithography to multiply copies for the pupils, and is said to have invented the chalk composition in its present form, or at least to have improved it greatly.

From this period, the practice of the art has extended and improved rapidly, and more particularly at Munich, where several establishments were formed for the purpose of applying it to the fine arts, as well as for printing writings and official forms for the different departments of the government.

In October 1809, Senefelder was appointed inspector of the royal lithographic establishment at Munich, for printing from stone a complete map and survey of Bavaria; after which period he devoted his time to experiments, and to writing the history of his invention. Among other points of improvement to which his attention was directed, was a substitute for the stones, which are inconvenient to use on account of their weight; and they are also liable to break in the press, when used without due caution, or when they contain flaws. For this purpose he made a composition of drying oil, finely ground earth, and other substances, which was thinly spread over pieces of parchment; but nothing of this sort has hitherto been found to answer. The surface cracks after repeated wetting and exposure to the power of the press, and the printing ink then enters the cracks, and spoils the impressions. Thus a very small number only of good impressions can be obtained. A public exhibition of printing from this stone paper was made in London, on the 23d July 1821, by a partner of Mr Senefelder; but the result was not such as to induce much confidence in the ultimate success of the trials to form this desirable substitute of a light material for a heavy one.

In England lithography was never entirely given up from its first introduction in 1800, although it was but little practised after 1806, till its revival at the latter end of 1817. Since then it has been most sedulously cultivated, and with such success, that its importance as a branch of trade is now almost equal to the art of engraving.

In France but little was done in lithography till 1815, when it was established at Paris by Lasteyrie, and being taken up by good artists, it soon attained great excellence.

Since this period it has extended most rapidly, and there is not now a town of any importance, either in Europe, North America, or in the East or West Indies, where lithography is not practised.

II. DESCRIPTION OF THE MATERIALS, AND THE MODE OF PREPARING THEM.

I. Of the Stones, and the manner in which they are prepared to receive the Drawings.

As calcareous stones will all imbibe grease and moisture, and effervesce with an acid (the use of which will appear when we speak of the process of printing), they are all capable of being used for lithography. Those are best adapted to the purpose which are very compact, of a fine and equal grain, and free from veins, or imbedded fossils or crystals.

The quarries of Solenhofen, near Pappenheim, in Bavaria, furnished the first plates, and none have as yet been found to equal them, in quality. They are of a very uniform pale yellowish-white colour. The fracture is perfectly conchoidal. The beds divide into thin portions of considerable size, with perfectly flat surfaces, and were on this account carried to Munich, and other places, for paving kitchens and halls, and thus came in the way of Senefelder, when he discovered the chemical process of printing.

The stones of this quarry vary in their quality, but the best may be had in great abundance. Generally speaking, the hardest are the best, provided they are quite uniform in texture. Such are necessary for fine chalk drawings; softer ones may do for ink, or for coarser drawings in chalk.

In France, stones have been found near Chateauroux [Departement de I Indre), of a similar colour to those of Solenhofen, and even harder and of a finer grain; but they are so full of large spots of a softer nature, that it is scarcely possible to get one perfect of a greater size than twelve inches square.

In England, a stone has been used for lithography which is found at Corston, near Bath. It is one of the white has beds, but not so fine in grain, or so close in texture, as the German stone, and therefore far inferior. But it is good for transfers, and does tolerably well for ink drawings or writings. Another stone, found near Stony Stratford, is also used; but it is of a brownish-gray tint, [7:13:382] and too dark in colour to show the effect of the drawing with sufficient clearness.

To bear the pressure used in taking the impressions, a stone twelve inches square should be at least an inch and a quarter thick. The thickness must increase with the size of the stone, but two inches and a half are a thickness sufficient for stones of three feet by three feet and a half.

The stones, when sawn to a proper size and thickness, are ground level by rubbing two of them face to face with water and sand, and very carefully examined with a straight-edge, to ascertain that they are perfectly level in all directions. This applies only to the side which is afterwards to receive the drawing, as the natural division of the stone is sufficiently true for the back.

To prepare them for chalk-drawings, two stones, which have been perfectly levelled, are well washed, in order to free them from any of the coarser grains of sand which have been previously used upon them. They are now to be placed on a board over a trough, and a small quantity of water and fine sand being strewed over the surfaces, they are to be rubbed face to face, adding occasionally a little fresh sand and water. The best sort of sand in England is that called silver sand for preparing the stone, and the common brown sand for giving a fine grain. The sands must be passed through a sieve of the fineness required, which will vary with the nature of the drawing; and the greatest care must be taken to have the sieves perfect, and to prevent any coarser particles of sand from being mixed with the rest. A single grain would fill the stone with innumerable scratches, which would all appear in the drawing. The upper stone is in this operation moved in small circles carefully and equally all over the under one, taking care not to move the one beyond the edge of the other, or the faces would become rounded. When the grain is equal, and sufficiently fine, the stones are carefully washed, and wiped with a clean cloth. The stone, thus prepared, should have, when dry, a perfectly uniform appearance in the colour and grain, and resemble a sheet of vellum. It should be free from scratches, and have no shining parts. The upper stone is always the finer grained of the two.

To prepare the stones for ink drawings or writings, the process just described is first followed; they are then well washed to get rid of the sand, and the same operation of rubbing two together is continued with powdered pumice-stone and water. When perfectly smooth, they are again washed, and afterwards separately polished with a large piece of fine pumice-stone, or Water of Ayr stone. The polish now given to the stone should be such as to show the reflection of objects to the eye placed close to the stone, and looking along it towards the light.

When a writing or drawing has been fully used, and the stone is to be again prepared, sand is strewed over the surface, and it is sprinkled with water, and rubbed with another stone, as before described, till all traces of the drawing has disappeared. After this, the stone is again prepared for a new drawing with fine sand, by being grained or polished, as before.

Ink drawings sink deeper into the stone than the chalk, and require the stone to be more ground away to efface them. The longer drawings remain upon the stone, the deeper the ink or the chalk penetrates.

2. Lithographic Ink and Chalk.

For these materials, the union of several qualities is required; and as no single substance possesses them all, it is necessary to combine several substances together.

Lithographic Ink.

The qualities required in lithographic ink, by which is meant the ink for drawing on stone, are, first, that it shall have in its composition such a quantity of greasy or fatty matter as will secure its imparting to the stone, even when it is laid on in the most delicate lines, a trace strong enough to attract readily the ink afterwards to be applied by the roller; and, secondly, that this ġrease be so prepared, by being mixed with alkali and other substances, as to be easily soluble in water, and to flow readily from the pen or brush when used for drawing. Many receipts have been given for this purpose, but the following is one of the most approved; and, ordinary care being taken in its preparation, it will be found to answer.

Composition of Lithographic Ink for draining on Stone.

Tallow candle 2 oz.

Virgin wax 2 oz.

Shell lac 2 oz.

Common soap 2 oz.

Lamp black, about one twentieth of the whole.

These materials are prepared in an iron saucepan, with a cover. The wax and tallow are first put in 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 shell lac 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, after the process above described, any parts are not completely melted, they must be dissolved over the fire without being again ignited.

Sometimes a larger proportion of wax is used, when only half of the soap is put in, and the burning goes on until the quantity is reduced one half. The remainder of the soap is then added over a fire which keeps the mass melted without igniting it.

The black, being previously mixed with thick varnish, such as will be described when we come to treat of printing inks, should now be added; and when it is completely dissolved, the whole mass should be cast on a marble slab, and a heavy weight laid over it, to render its texture fine. When cold, though not so hard, it should in its fracture have an appearance resembling Indian ink.

So much here depends upon the manipulation, that even the most experienced person can never be sure that the desired result is altogether attained, until the product is subjected to experiments; the mass may have been burned a little more or a little less than enough; too much or too little time may have been allowed to elapse betwixt the putting in of one ingredient and another: such circumstances, trifling as they appear, are quite sufficient to render the ink altogether unfit for use. It not unfrequently happens, therefore, that such faults as the following are to be found: If it has been too little burned, it may appear soft, and, if soluble, it may, when mixed with water, speedily become thick and slimy, in which case it must be re-melted and burned a little more; but if, on the other hand, it has been burned too much, it may appear to be composed of sand, and, when used, although it will flow pleasantly enough, may not have enough of grease left in it to attract the printing ink when applied. This fault may be corrected by remelting it, and adding a small quantity of soap and wax.

Keeping in view the principles here pointed out, any one can, alter a few trials, make good lithographic ink.

Ink for Transfers.

This ink may be composed of the same materials as the ink for drawing on stone, with the addition of a little more [7:13:383]wax. If it is too little burned, the lines of the writing or drawing will spread on being transferred to the stone; if too much, a sufficient quantity of grease will not be imparted to the stone to attract the ink from the roller when it is applied: but either of these defects may be corrected as before directed.

Lithographie Chalk.

This should have the qualities of a good drawing crayon; it should be even in texture, and carry a good point. It is, however, difficult to avoid making it too soft and greasy On the one hand, and too brittle on the other. For the chalk, as for the ink, more or less of the soap, wax, and tallow may be used, as the extent of the burning may render necessary; and the remedies pointed out for defects of the ink will enable the operator to judge of what is wanting.

The following proportions are the best:

Common soap 11 oz.

Tallow 2 oz.

Virgin wax 2į oz.

Shell lac 1 oz.

The manipulation is similar to that for the ink. It is well, however, to throw in a little of the wax just before the flame is extinguished. Less black must be mixed with the chalk than with the ink, its only use being to colour the drawing, so that the artist may see the lines he traces.

When the whole is well mixed, it should be poured into a mould, and very strongly pressed to prevent any bubbles, which would make the texture irregular.

3. Mode of Drawing.

Wsth these materials the artist proceeds to work on the prepared stone, taking care first to wipe the stone with a clean dry cloth. The ink being rubbed with warm water like Indian ink, is used on the polished stone; and it is to be observed, that a gradation of tints can be obtained only by varying the thickness of the lines, and the distance at which they are placed apart, as the line traced by the ink, being sound and unbroken throughout, receives the printing ink all over. Hence it follows, that the artist cannot gain any advantage by diluting the ink for the lighter tints of the drawing, as the printing ink will take effect equally upon all the lines, and at once render all of them equally black. The object of the artist is to mix the ink to that consistency which, whilst it works freely, shall yet be strong enough to stand perfect through the process of printing. A consistency a little stronger than writing ink is sufficient for this purpose.

The chalk cannot be used upon the polished stone.

The grained stone, prepared for chalk, being carefully wiped to free it from dust, must be drawn upon with the crayon as common drawing chalk is used on paper. The subject may be traced on the stone with lead pencil or red chalk, but care should be taken to do this very lightly, so as not to fill up any of the grain of the stone. In drawing, the degree of pressure of the hand will vary the strength-of the tint, and it is desirable to give the requisite strength at once, as the surface of the stone is a little altered by receiving the chalk, and hence it does not take any additional lines with the same equality. Practice is necessary to give a command of the material, as it does not work quite like the common crayon, there being great difficulty in keeping a good point. There is also much difficulty in obtaining the finer tints found in the impression; and for the light tints it is necessary to put the chalk in a reed, as the metal port-crayon is too heavy to draw them, even without any pressure from the hand; and therefore the artist cannot draw them with freedom, as his touch will be unsteady, by being obliged to support the pencil from the stone.

It is necessary to observe the grain with which the stone is prepared, which should vary with the fineness of the drawing. Several pieces of chalk should be prepared to use in succession, as the warmth of the hand softens it.

It is useful to cut the chalk in the form of a wedge rather than a point, as it is less likely to bend in that form.

Small portions of the point will break off during the drawing; and these must be carefully removed with a small brush.

4. Printing Press and Poller.

' The printing press for lithography does not differ materially from the ordinary copperplate press. A detailed description of one of the most approved construction will be given under the article Printing. The Poller.

The following is a representation of the roller:

The length may vary, but it ought to be full 1 four inches in diameter. It is covered with flannel, rolled tightly three or four times round, and nailed at the ends. It is then covered with a stretched calf-skin, fitting quite tight. The scam must be made neatly with the boot-maker’s closing stitch. The ends of the leather are gathered with a string, and tied round the projecting ends of the roller. Loose handles, A, A, made of thick leather, are put on these ends when it is used. The leather must be put on the roller with the smooth side outwards.

5. Printing Ink.

The printing ink is composed, as other printing inks are, of oil, varnish, and very fine lamp-black, well mixed together. To prepare the varnish, a saucepan is about half filled with pure linseed oil, and heated over a fire till it ignites from the flame of a piece of burning paper. It should then be allowed to burn till it be reduced to the degree required; and if, during the operation, there appear danger of its boiling over, it should be immediately taken off the fire, and the cover, which ought to fit quite close on the saucepan, must be put on to extinguish the flame. This is to prevent accidents; and the operator cannot be sufficiently cautioned against the danger attending the burning of the varnish, which ought never to be performed in a room with a boarded floor, or indeed in any part of a house. Wet sacks are the best things to put out the flame in case of accident.

Several inks must be prepared, differing in the degree of viscidity, or thickness of the varnish from which they are made, and the quantity of black mixed with them. The longer the oil is burned, the thicker the varnish becomes. The thinnest varnish is burned till it has lost nearly one fourth of its volume; the next till it is reduced one third; the thickest till it is reduced one half.

These directions are to be considered as very general ones; and the state of the varnish is best judged of during the burning, by taking out some with a spoon, and letting a drop fall on a cold earthenware plate, and trying its degree of viscidity with the finger. The thinnest sort should be like common honey, and the other should draw out in strings, which will be longer as the varnish is thicker. The thickest will draw out in strings two or three feet in length.

It is quite essential to have the oil pure, and the saucepan perfectly clean, and to keep the varnish in clean close [7:13:384]jars in a cool place. It is best not to make the varnish long before it is wanted; for if any decomposition takes place in it, the drawing will be spoiled by the printing ink. The black is mixed with the varnish on a grinding stone with a muller, in small successive quantities; care being taken that the first portion of black is equally mixed with the varnish before a second is added. In the thickest inks this requires considerable labour. By mixing the varnishes together, any degree of stiffness of the ink may be obtained; and by putting more or less black, its thickness is regulated. The printer must always have by him several small pots, each containing a different printing ink, to be used as occasion requires. A small quantity, not more than the size of a hazel-nut, should be used at a time; for it is desirable to charge the roller with as small a quantity as possible. It must be worked well on the colour table with the roller in all directions, that it may be equally distributed all over the roller. Ink drawings are generally printed with a stiffer inkjhan chalk drawings.

6. Preparation of the Stone for Printing.

The drawing being finished on the stone as before described, is sent to the lithographic printer, on whose knowledge of his art the success of the impressions in a great measure depends. The first process is to etch the drawing, as it is called. This is done by placing the stone obliquely on one edge over a trough, and pouring over it nitric acid very much diluted. It is poured on the upper part of the stone, and runs down all over the surface. The stone is then turned, and placed on the opposite edge, and the etching water, being collected from the trough, is again poured over it in the same manner. The degree of strength, which is little more than one per cent, of acid, should be such as to produce a very slight effervescence; after the etching water has lain on the stone for a second or two, its strength must vary according to the heat of the atmosphere and the degree of fineness of the drawing. It is desirable to pass the etching water two or three times over the darkest parts of the drawing, as they require more etching than the lighter tints; and when the drawing is fine, a little green should be mixed with it. Some stones also, and different chalks, require different degrees of strength of the acid; and experience alone can guide the lithographer in his practice on this point. Chalk drawings require weaker acid than the ink.

The stone is now carefully washed, by pouring clean rain-water over it, and afterwards with gum-water; and when not too wet, the roller, charged with printing ink, is rolled over it in both directions, viz. sideways, and from top to bottom, till the drawing takes the ink. It is then well covered over with a solution of gum-arabic in water, of about the consistency of oil. This is allowed to dry, and preserves the drawing from any alteration, as the lines cannot spread, in consequence of the pores of the stone being filled with the gum. After the etching, it is desirable to leave the stone for a day, and best not to leave it more than a week, before it is printed from. In some establishments a few proofs are taken immediately after the drawing is etched, but it is better not to do so.

The operation of the etching requires great nicety, and must be done quickly. If the drawing is etched too strongly, the fine tints disappear; if too weak, the printing ink mixes with the darker parts, and the drawing runs into blots. A soft stone requires weaker acid than a hard one, if they are equally pure in quality. The differences in the composition of the stones also require differences in the strength of the etching water, so that no strict or certain rules can be given.

The effect of the etching is, first, to take away the alkali mixed with the drawing chalk or ink, which would make the drawing liable to be affected by the water; and, secondly, to make the stone refuse more decidedly to take any grease. The gum assists in this latter purpose, and is quite essential to the perfect preparation of the surface of the stone.

7. Printing.

When the stone is to be printed from, it is placed on] the bed or platten of the press; at this time a proper sized scraper for the printing is very carefully adjusted to the surface of the stone. The gum on the stone is now sprinkled with rain-water, and being gradually dissolved, and a wet sponge passed lightly all over it, the printer works the ink which is on the colour table placed beside him, with the roller, in all directions, till it is equally and thinly spread all over the roller. He then, the stone being wet, passes the roller all over the stone in both directions, observing, as his experience enables him to do, that all parts of the drawing take the ink in due proportion. The roller should be applied with an equal motion and pressure, which must be regulated according to the mode in which the drawing takes the ink; if it does not take it readily, the pressure must be increased, [and the roller moved more slowly. The roller should turn freely as it passes over the stone; if it slips, the cause is either that the stone is too wet, or that too much of the gum remains upon the stone; in the first case, a drier sponge will correct the evil; in the second, the stone must be again washed with a little water; but this must be done with caution, as the gum· should not be entirely washed off the stone.

At first the drawing receives the ink with some difficulty, and it is frequently necessary to wet the stone and roll it in several times, before it will take the ink readily. Care must now be taken not to wet the stone too much; the less dampness the better, provided it is sufficient to keep the stone from taking the ink in the parts where there is no drawing; at all events, no drops of water should be seen upon the stone, as they spoil the printing ink, and also are imbibed by the roller, which therefore becomes unfit for use. After the drawing is thus rolled in, the sheet of paper is placed on the stone, and the impression taken in the manner described in the account of the press. When, after the impression, the paper is taken up, the stone appears dry, the moisture having been imbibed by the paper. It must be again wetted with a damp sponge, and rolled in with ink as before, taking care to work the roller well on the colour table each time before applying it to the stone.

Generally the first few impressions are imperfect, from the drawing not taking the ink fully; but this is gradually corrected in the succeeding impressions.

During the printing some gum must always remain on the stone, though it will not be visible, otherwise the ink will take on the stone, and also spoil the drawing. If, by too much wetting, or by rubbing too hard with the sponge, the gum is entirely removed, some fresh gumwater must be laid on. If the stone has, in the first instance, been laid by with too small a quantity of gum, and the ink stains the stone on being first applied to it, gum-water must then be used to damp the stone instead of pure water. Sometimes, however, this may arise from the printing ink being too thin, as will appear below. If some spots on the stone take the printing ink, notwithstanding the above precautions, some strong acid must be applied to them with a brush; and after this is washed off, a little gum-water is dropped on the place. A steel point is here frequently necessary to take off the spots of ink. The edges of the stone are very apt to soil, and generally require to be wiped with an old sponge or rag [7:13:385]after the rolling in. They must also frequently have an application of acid and gum, and sometimes be rubbed with pumice-stone. Chalk drawings are much the most difficult to print. After this general description of the printing, the following development of the principles on which it is regulated, and notice of the difficulties which arise in its progress, will be found useful. An ink which is too thin, and formed of a varnish not sufficiently burned, will soil the stone, notwithstanding that the proper precautions are taken of wetting the stone, and preparing it properly with acid and gum. Ink which is too stiff will tear up the lighter tints of the chalk from the stone, and thus destroy the drawing.

The consideration of these circumstances leads us at once to the principles of the printing. These accidents arise at the extreme points of the scale at which the printing inks can be used; for it is evident, that the only inks which can be employed are those which are between these points, that is, thicker than that which soils the stone, and at the same time thinner than that which takes up the drawing. Any increase of temperature will diminish the consistency of the printing ink; the stone will therefore soil with an ink which could be safely used at a lower temperature; hence a stiffer ink must be used. Now, if the temperature should increase so much that the stone will soil with any ink at all less thick than that which will take up the drawing, it is evident that the printing must cease till, by standing, the lines of the drawing shall have acquired additional strength. This, though it sometimes occurs, is a rare case; but it shows that it is desirable to draw with a chalk or ink of less fatness in summer than in winter; and also, that if the printing-room is in winter artificially heated, pains should be taken to regulate the heat as equally as possible.

We will now enumerate some other difficulties which are not referrible to the above general principle.

If the pressure of the scraper is too weak, the ink will not be given off to the paper in the impression, although the drawing has been properly charged with it. Defects will also appear from the scraper being notched, or not correctly adjusted, or from any unevenness in the leather or paper.

Inequalities in the roller will cause the drawing to receive the ink unequally, and if the roller or its leather is too hard, it will not ink the drawing clearly.

After printing a considerable number of impressions, it sometimes happens that the drawing takes the ink in dark spots in different parts. This arises from the printing ink becoming too strongly united with the chalk or ink of the drawing, and if the printing is continued the drawing will be spoiled. A little consideration will show us the reason of this accident. The printing ink readily unites with the drawing, and being of a thinner consistency, it will by repeated applications accumulate on the lines of the drawing, soften them, and make them spread. In this case it is necessary to stop the printing, and let the stone rest for a day or two, for the drawing to recover its proper degree of hardness. If the drawing should run smutty from any of the causes before enumerated, the following mixture will clean it.

Take equal parts of water, spirits of turpentine, and oil of olives, and shake them well together in a glass phial, until the mixture froths; wet the stone, and throw this froth upon it, and rub it gently with a sponge. The printing ink will be dissolved, and the whole drawing also will disappear, though, on a close examination, it can be distinguished in faint white lines. On rolling in again with printing ink, the drawing will gradually re-appear as clear as at first.

Accidents sometimes occur in the printing, from the t qualities of the paper. If the paper has been made from rags which have been bleached with oxymuriatic acid, the drawing will be incurably spoiled after thirty impressions.

Chinese paper has sometimes a strong taste of alum; this is so fatal as sometimes to spoil the drawing after the first impression.

When the stone is to be laid by after printing, in order that it may be used again at a future period, the drawing must be rolled in with a preserving ink, called by Senefelder, actzfarbe, as the printing inks would, when dry, become so hard, that the drawing would not take fresh printing ink freely. The following is the composition of the preserving ink.

Thick varnish of linseed oil 2 parts.

Tallow 4 do.

Venetian turpentine. 1 do.

Wax 1 do.

These must be melted together, and then four parts of lamp-black very carefully and gradually mixed with it, and it must be preserved for use in a close tin box.

Very fine effects are produced in lithographic prints, by printing from two or more stones with different coloured inks. This is managed by preparing a composition of

Wax 2 parts.

Soap 1 do.

A little vermilion.

Melt them in a saucepan, and cast them into sticks. This must be rubbed up with a little water to the thickness of cream, and then applied to the surface of a polished stone. An impression is taken in the common way from a drawing, and applied to a stone prepared in this manner, and passed through the press, care being taken to mark, by means of this impression, two points in the margin corresponding on each of the stones. The artist having thus on the second stone an impression from the first drawing to guide him, scrapes away the parts which he wishes to remain white in the finished impression. The stone must now be etched with acid stronger than the common etching water, having one part of acid to twenty of water. The whole is then washed off with turpentine.

This plan has been very much followed at Munich, and in this country some splendid specimens have lately been produced. It is generally used to print a middle tint from the second stone. The black impression being given from the first stone, a flat transparent brownish tint is given from the second, and the white lights are where the paper is left untouched. The dots are necessary to regulate the placing of the paper on the corresponding parts of the two stones.

The coloured inks for the tints are differently made, according to the tint required, but the varnishes alone make very good light browns.

The paper for lithographic printing should not be so damp as for copperplate printing.

8. Different manners of Lithography.

Besides the manners already described of drawing with ink and chalk, lithography is practised in various other ways.

Transfers.

The most useful of these is the transfer before alluded to in speaking of the inks, as it saves the labour and inconvenience of writing backwards. This is performed by writing with the composition ink on a prepared paper, and then transferring the writing to a stone, by passing it through the press.

Dissolve in some water half an ounce of gum-tragacanth, to which, after it is well mixed and strained, add one ounce of glue and half an ounce of gamboge.

Then take of French chalk 4 ounces.

old plaster of Paris.. ⅜ ditto, starch 1 ditto.

Powder these, and sift them through a fine sieve; grind [7:13:386]them with a portion of the gum-tragacanth, glue, and gamboge; then add sufficient water to give it the consistency of oil, and apply it with a brush to thin sized paper. The writing must be made with the ink on the prepared side.

When the transfer is to be made, a polished stone is warmed to about 130° Fahrenheit, and placed in the press. The paper is then carefully damped at the back with a sponge, and placed between some sheets of soft paper. It is next placed on the stone with the writing towards it, and passed through the press as in printing an impression. This must be repeated four or five times without raising the leather cover of the bed of the press, beginning with a slight pressure at first, and increasing it every time. The press is now to be opened, and the paper, being damped, taken off, when the writing will appear to have come off the paper on the stone.

When the stone is quite cold, it is etched and prepared for printing in the usual manner.

This mode is peculiarly valuable for maps, plans, writings, &c. when expedition and economy are objects of importance; and the impressions produced by skilful lithographers retain all the purity and sharpness of the original drawing or writing.

Imitation of Wood Cuts.

This is a very easy mode, though not much practised. A polished stone is covered all over with lithographic ink, and the parts which are to be left white are scraped away with a steel point. Very fine lines are most easily obtained by putting them in with a hair pencil. The stone is etched as before described.

Etchings on Stone.

A polished stone is prepared for this mode by washing it with diluted acid as weak as the water used for etching a drawing; and after that is washed off, and the stone is dry, it is to be covered with weak gum-water and a little lamp-black. This forms a coating to the stone, and the artist works on it with an etching needle, as in etching upon copper. The lines which he traces appear white, but look stronger than they will appear afterwards. The stone should be a little warmed, for the needle to work freely through the coating, and care must be taken not to breathe upon it. When the etching is finished, the surface is to be rubbed all over with linseed oil, which penetrates into the lines drawn by the needle. After this the coating is to be all washed off with water.

In this mode lines can be drawn as fine as on copperplate; it is, however, but little practised in England, though it is often employed in Germany.

The great distinction between lithography and engraving, when employed for works of art, is, that the former gives a fac-similé of an original drawing, which retains all the freedom and touch of the artist’s own hand; whilst, on the contrary, an engraving must be a copy. This character in a lithographic print arises from the facility with which the drawing is produced, as the process is exactly that which the artist would follow in making a common drawing: and the farther advantage of a great saving of expense is derived from the same cause; for the drawing being made at once on the stone, the whole expense of the engraving is saved. This is particularly the case with drawings in chalk, or with outlines or slight works in ink; and thus the door is opened to the production of many works which could not otherwise be published on account of the expense of engraving.

The more finished drawings in ink, however, have not the same advantages, for the gradations in tint can be obtained only by the variations in the breadth and distance of the lines, which is the same principle as that on which the engraver works; and hence the labour is more nearly equal in the two methods.

There is, however, much less difficulty in drawing lines on the stone than in cutting them on copper, and of course the operation is less expensive; and the cost of printing from stone is also considerably under that of printing from plates, which renders the employment oslithography doubly advantageous when a large number of copies are required. The number of impressions that may be taken from a chalk drawing varies according to the fineness of the tints and the manner in which the drawing has been executed. Some drawings will be exhausted by 1500 or 2000 copies, others have stood 20,000, and some even 30,000 impressions.

Ink drawings and writings give considerably more; the finest, if properly managed, will give from 6000 to 10,000; others it seems to be impossible to exhaust, hundreds of thousands having been printed from some without any material injury.

The advances which lithography has made within these few years have been really immense. Specimens in the chalk manner have been produced which vie in beauty with the stippled engravings in the line manner. Efforts equally wonderful have been made, and there seems no reason to doubt that further improvements will yet be effected in this infant art. The external delicacy of tint of the finest engravings there is reason to believe, as has already been shown, it never can equal; and it is more than probable that the station which it has already attained, is that which it is destined to fill; that is, betwixt the first class of engravings and the middling productions of copper and steel, its greatest advantages being economy and expedition in the execution. The innumerable instances in which the public have already been presented with valuable works by means of lithography, which could not have been produced by the more expensive and tedious mode of engraving, are sufficient evidences of its vast importance, and afford ground for the anticipation of still greater benefits.