Practical Lithography

Elementary Details

Concerning Stones-Character and Texture-Some Simple Elements-Preparation of Stones-Planing and Levelling-Grinding Grained Stones-Descriptive Treatment-American Method.

There are a vast number of details in connection with lithography and lithographic printing which are indisputably elementary in their character. It would be impossible, however, to regard them as non-essential, and a just appreciation of their value and influence must of necessity enter into any comprehensive exposition of the craft.

Stone as a printing medium.-The value of the Bavarian limestone was one of those fortunate discoveries which tended to materialise lithography as a graphic art, and may even be regarded as a fundamental principle, the practical value of which is only equalled by its far-reaching effects.

Other printing surfaces have been discovered and developed, with more or less substantial results, yet without depreciating their merits, it will be but a fair recognition to concede the premier position to the Solenhofen and other limestones of a like nature.

The homogeneity and porosity of these stones render them peculiarly suitable for lithographic purposes, and it undoubtedly reflects a vast amount of credit upon Senefelder that even at the outset he should select a medium so well adapted and in every way so eminently suitable for graphic reproduction.

I have already, and almost inadvertently, indicated the peculiar value of the Bavarian stone, for homogeneity and porosity of texture are absolutely essential properties, and upon these is based almost every theory which has assisted in the development of this craft. These properties, in conjunction with a suitable greasy pigment, provide the requisite materials for that cause and effect which require and compel consideration.

The simple elements of lithography may be very briefly described, and in this direction at least we must follow certain well-defined lines which may be regarded as well-worn ruts, the consideration of which offers little that is new.

A brief review of the theories of chemical and mechanical affinities is best calculated to impress upon the mind the elementary principles of the lithographer's art.

The penetrative power of a greasy pigment, together with the porous nature of the litho-stone, may be regarded as the cause by which the lithographer produces as an effect a design or impression which, to some extent, enters into the texture of the stone-the homogeneity of which checks any tendency to spread. This fatty matter may be applied in one or two ways, either as a transfer from some other printing surface, or as a direct drawing with pen, brush, or crayon.

The first question for consideration will be the initial preparation of the litho-stones. These preparatory operations-which have for their object the levelling, polishing, and cleaning of the stones-were at one time entirely performed by hand labour, but are now accomplished with much greater facility and in a more effective manner by machinery. The importance of each individual operation will be more readily appreciated when once its purpose is clearly understood. A litho-stone having a perfectly level surface is necessary in order to enable the printer to secure a firm and uniform pressure over the whole design when printing therefrom. A smooth, polished surface will readily receive the finest designs, and retain all their original characteristics. A clean surface is an absolute necessity, i.e. a chemically clean surface free from grease or any foreign matter which would be likely to enter into the texture of the stone and by so doing injure any greasy drawing or transfer which might be made thereon.

These are simple, elementary principles, and as such are probably familiar to every reader, but the frequent result of familiarity is a dangerous tendency to under-estimate the importance of everyday causes and effects. If, therefore, such a reference as the above to common details serves to convey some intelligent idea of their place and true value, then no apology whatever will be necessary for their insertion in this volume. It has already been stated that, in the preparation of litho-stones, the superseding of hand labour by machinery has effected considerable and important changes.

Several machines, all of more or less practical value, have been introduced to the trade. One of the more recent developments, a stone-planing machine, possesses many features of real merit (Fig. 1).

The stone is securely fixed on a perfectly true bed and passes slowly to and fro beneath the blades of powerful cutting knives. These blades are arranged in an inverted V-shape and locked in an oscillating framework. By an automatic action they are almost imperceptibly lowered at each traverse of the machine, when they lightly cut away the surface of the stone until the old work is completely removed and a smooth level face is assured. The chief objection to this type of machine is that in course of time the knives become worn and slightly irregular, and it is but reasonable to suppose that when a number of small stones have been operated upon and immediately afterwards a full-sized stone is planed, such irregularities will be very pronounced and detrimental.

Fig. 1.

Many machines have been designed on the simple grinding principle, but one type differs from its contemporaries and offers several distinct advantages over them (Fig. 2).

This machine is constructed on hand-polishing lines, i.e. the movements are to some extent mechanical arrangements of hand-polishing principles. The size of stone makes no difference whatever, and the results are in the main uniform and satisfactory. The inconveniently sharp edges, such as are produced by the planing machine, are unknown,-the wear and tear on the stone is perceptibly lessened, and the power required to drive such a machine is not by any means a serious matter.

When a planing machine does not enter into the operation, and grinding by hand is therefore necessary, sharp, clean sand should be used as a grinding medium. To secure some degree of uniformity in the grain, and at the same time remove all the larger particles of grit, pass the sand first through a fine sieve. The harder qualities of sand have, of course, the greatest cutting power, and therefore are the most suitable for this purpose.

Fig. 2.

When hand-grinding is resorted to, a continuous elliptical motion of one stone over the other with a slight twist from the wrist will prove most effective.

To finish the grinding, and as far as possible remove the deeper sand scratches, work off the sand in the form of a sludge. Unless this operation is carefully and patiently performed, scratches of considerable depth may appear on various parts of the stone's surface. These, in the subsequent polishing, may offer a strong temptation to the operator to work over one part of the stone more than another, so as to effect the removal of such scratches with greater rapidity. The almost certain result of this would be an uneven surface, which would in many ways prove troublesome to the printer.

The graining of stones.-This is a matter concerning the preparation of stones which must not be overlooked. The introduction of shading mediums and other contrivances of a similar character has considerably minimised the importance of the grained stone, inasmuch as it cannot now be regarded as an indispensable feature of lithography. It is, however, still of inestimable value, and will probably always find a place and purpose in the practice of lithography, despite its depreciation owing to present-day limitations.

Recognising, then, the possibility of its retention, at least for some time to come, as a suitable printing surface upon which the lithographic draughtsman can work with undoubted facility of execution and effect, we must perforce include a brief description of its preparation in this chapter.

First of all, level the stone and to some extent polish it, after which the graining may be proceeded with. A glass muller about 6 or 7 inches in diameter makes an excellent "grainer." Failing this, a handy substitute will be found in the form of a small litho-stone, hard in texture, and with a smooth, level surface. Use as a graining medium sharp, clean silver sand only, passing it carefully through a sieve according to the size or depth of the grain required. Sprinkle a little of this sand uniformly over the stone under treatment, together with a few drops of clean water. With a continuous circular movement pass the graining muller from end to end of the stone, exerting a firm and uniform pressure. Repeat this operation again and again, adding sand and water as required. Considerable time coupled with intelligent application will be necessary to carry out this work successfully. Should the sand become too much worn before its renewal the grain will in proportion lose its "tooth" or sharpness. On the other hand lies the danger of producing a grain which is too harsh or pronounced. Therefore much depends upon the skill and judgment of the operator. A safe plan is to ascertain the progress at any time when a satisfactory result might be reasonably expected. The best way to accomplish this is by washing from the face of the stone any accumulation of sand, and drying it, so that a test can be made with the actual grade of crayon to be used in the subsequent drawing. A powerful current of clean, cold water affords the best means for removing every trace of sand from the finished stone, and will leave it in a condition of almost complete readiness for the draughtsman; a good drying is then all that is necessary. Good results have been claimed for a method of graining which was introduced by the Americans a few years ago. In this process the grain is produced by sprinkling the surface of the stone with sand and rolling it with small glass balls. These balls having a limited area in which to work exert a continuous cutting power without any tendency to produce scratches. Some mechanical arrangement is necessary to impart this continuous rolling movement to the glass balls and to maintain a uniform speed. It is quite easy to understand that with such a process, carried out under favourable conditions, very fine results might be produced with great rapidity.

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Lithographic Transfer Inks

Various Forms-Distinguishing Features-Formul?-Writing Transfer Ink-Stone-to-stone Transfer Ink-Copperplate Transfer Ink-A Modification.

Given a perfectly clean and smooth polished stone as described in the previous chapter, the next important point is the composition of the fatty matter wherewith a design or drawing is applied.

As already stated, the active principle in any suitable transfer medium of this character is invariably the same, no matter what form its composition takes. For applying with pen or brush it must possess soluble properties, and of necessity be reduced to a liquid form. Such soluble properties, however, must not interfere with its fatty properties, these latter being essential features.

In crayon or chalk drawing the composition must be employed in a concrete form, as a crayon, the hardness and texture of which will be controlled (1) by the character of the work to be carried out; (2) by the character of surface to be operated upon.

Transfers from other printing surfaces can only be made when the composition used is in the form of a pigment, and reduced to a convenient working consistency.

These, then, comprise the varieties of transfer mediums which are likely to be required in most phases of commercial lithography. Others are, of course, employed for specific purposes and under peculiar conditions; but these, again, are more or less modifications of existing formul?, prepared to meet particular requirements.

The ink used for transferring impressions from one printing surface to another, e.g., the re-transferring of work from stone to stone, may with a very slight alteration serve for type to stone transfer; but a considerable departure must be effected to produce a satisfactory photo-litho transfer ink, while a composition of a peculiarly distinctive character will be requisite for the successful production of transfers from copperplate engravings, as well as for a transfer ink for writing and drawing on stone or transfer paper. This writing transfer ink must be soluble in water, yet without becoming slimy; otherwise it will not work freely with the pen or brush. It must also dry quickly, and without any tendency to smear.

A plate transfer ink must neither melt nor drag when applied to the hot plate. It must, of course, soften sufficiently to fill in the lines of the engraving, and should so harden as it cools that it cannot easily be dragged away during the cleaning and polishing operations. See Chap. IV. page 19.

Each and all of the above inks must be excessively greasy and penetrative, but without having the slightest tendency to spread superficially. The ingredients and methods of preparation specified in the succeeding paragraphs are not given as standard formul?, but in corroboration of statements made, and as practical illustrations of the character and purpose of transfer inks and compositions generally.

Transfer ink.-Writing transfer ink, for writing or drawing on stone or transfer paper, may consist of equal quantities of:-

Castile soap,

Wax,

Tallow,

Shellac,

with the addition of carbon black or black printing ink as a colouring matter. Another reliable formula is:-

Soap 4 parts

Tallow 3 parts

Wax 6 parts

Shellac 4 parts

Carbon black 1 parts

Whichever formula is adopted the method of preparation is the same combination.

Free the soap from all moisture by drying, and thus facilitate its combining with the other ingredients.

Melt the tallow and wax over a hot fire until they are thoroughly well mixed. Add the dried soap a little at a time, so that it may become thoroughly incorporated with the wax and tallow. Bring the mixture to boiling-point, then remove it from the fire or stove and ignite the fumes which will then be rising freely. Continue the burning process for about fifteen minutes, then extinguish the flames by replacing the lid of the pan. The shellac and black may be added while the composition is cooling.

Stone-to-stone re-transfer ink.-The ingredients of this ink consist of:-

4 oz. Transfer ink.

4 oz. Litho black ink.

4 oz. Medium varnish.

1 oz. Canada balsam.

Melt the transfer ink over a slow fire and add the other ingredients separately.

Canada balsam will not only add to the effectiveness of this ink, but it will also improve its working qualities.

Copperplate transfer ink.-Ingredients consist of:-

1 oz. Tallow.

3 oz. Bee's wax.

4 oz. Shellac.

2 oz. Soap.

4 oz. Bitumen.

1 oz. Canada balsam.

1 oz. Carbon black.

The method in this case differs somewhat from the preceding. First melt the bitumen and then add the wax and soap in small pieces as before. Burn this for fifteen minutes, and add the shellac, balsam, and black, boiling the whole gently for forty minutes. Mould into squares or sticks, and for convenience in handling cover these with tinfoil.

Should an extra powerful ink be required for shading or stippling films, the stone-to-stone re-transfer ink can be reduced to a working consistency with castor oil instead of varnish, and thus rendered suitable for this purpose.

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Lithographic Transfer Papers

Essential Features-Varnish Transfer Paper-Damp-stone Transfer Paper-French Transparent Transfer Paper-Copperplate Transfer Paper-An Alternative Recipe-Granulated Papers-Photo-litho Transfer Paper.

Transfer papers are even more used than the transfer compositions already described, and in greater variety, in consequence of which there is a wide difference of opinion concerning their merits.

To a certain extent the specific value of any transfer paper must depend upon local conditions. That which might be of the utmost value to one printer would in all probability fail to meet the requirements of another. With these also, as with the transfer inks, the main point is to grasp the general principles involved. Adhering to these principles enables any intelligent workman to adapt the transfers to his own peculiar necessity. It is most important that lithographic transfer paper should be absolutely impervious to the transfer composition or ink, so that an impression of full strength can be conveyed to the stone, leaving its greasy properties unimpaired. The paper therefore must undergo special preparation, and here again the character of the work and the conditions under which it is carried out are the chief controlling elements. So much is this the case that many lithographic printers prefer to make their own transfer paper, and find such a procedure eminently satisfactory.

A good bank post double foolscap paper, about 26 lb., first thinly coated with a solution of concentrated size and afterwards varnished with a heavy coach body varnish, gives excellent results. When transferring large work in which a number of printings are involved, and where accuracy of register is a sine qua non, the following mixture may, if desired, be substituted for the coach body varnish:-

Best oak varnish 1 quart.

Turpentine ? pint.

Boiled linseed oil ? pint.

Paper thus prepared rarely stretches or becomes distorted to any appreciable extent, and can be used with equally good results on either cold or warm stones.

Its keeping qualities are, however, limited; it is therefore advisable to utilise the transfer impressions with as little delay as possible.

This may be criticised as a somewhat primitive and old-fashioned transfer paper; but of the many transfer papers now in use, none can claim to be exactly new.

Another stone-to-stone transfer paper of the simplest possible character can be made by coating a good writing paper with the following composition. Soak 3 oz. of glue in 6 oz. of water for about 8 hours. Reduce 1 lb. of starch to a thick, creamy paste by rubbing it down in a little cold water and then adding boiling water until the required consistency is obtained. Mix the starch and glue together, and add a little gamboge or cochineal as colouring matter, so as to enable the printer to see at a glance which is the coated side of the paper. Spread this composition on the paper while it is still warm.

A transparent transfer paper with a soluble coating is frequently desirable, and for certain purposes may be strongly recommended. A French transfer paper meets such a requirement, and at the same time possesses many other excellent qualities. It picks up a firm, clean impression, and transfers every particle of it to the stone. It is also transparent, and sufficiently adhesive to stick to a very slightly damped stone under a light pressure.

A transfer paper which may be used as a base upon which to write or draw a design for subsequent transference to stone, as well as for stone-to-stone transferring, should be coated with a composition of a gelatinous character, which will not be readily soluble in water. Writing transfer ink is of course dissolved in water, and its effect on a soft, soluble composition would be disastrous.

The following formula is suggestive as well as practical:-

Gelatine 4 oz.

Isinglass 6 oz.

Flake white 3 lb.

Gamboge 2 oz.

Make a strong size of the above by boiling the gelatine and isinglass with a little water. Mix the gamboge and flake white with a little warm water, and add the mixture to the gelatine solution. This composition must be applied to the paper while still quite warm, as it forms into a comparatively stiff jelly while cooling. This paper should be transferred to warm stones.

Copperplate transfer paper is to some extent a development of the variety just described; that is, if the conditions under which such transfers are made will bear comparison with operations of an essentially different character.

The composition used for coating copperplate transfer paper must possess a somewhat heavy body, and for this reason plaster of paris enters into its composition, which is as follows:-

Plaster of paris 2 lb.

Flake white 1 lb.

Flour 2 lb.

Fish glue ? lb.

Alum 1 oz.

Soak the alum and glue from 8 to 10 hours, and then boil them until they are dissolved. Make the flour into a smooth paste by the addition of a little water, and mix it with the flake white. Mix the plaster of paris with water, and stir continuously until it becomes incapable of setting. Add the other ingredients, already mixed, and see that they become thoroughly incorporated with the plaster of paris, after which coat the paper twice with the mixture.

The following may be substituted for the above:-

Plaster of paris 2 lb.

Flour 2 lb.

Gelatine 4 oz.

A transfer paper with its surface granulated to represent a mechanical stipple, or the texture of a grained stone, may be prepared in the following manner. Take of:-

Starch 9 oz.

Parchment chippings 12 oz.

Flake white 14 oz.

Prepare the starch as previously described, and dissolve the isinglass by boiling. Mix the flake white into a thin paste by the addition of water. Warm the three ingredients, and mix the whole thoroughly. Coat a fairly heavy printing paper twice with this composition, and when it is thoroughly dry give it the required granulation by means of grained stones or engraved plates. The grain thus imparted breaks up the drawing into a series of minute dots. Paper of this description is most suitable for pencil or crayon work. Its usefulness is obvious. It enables the artist to use his chalks in the usual manner, without the inconvenience of handling large stones. No graining of the stone is necessary, and the grained effect can be confined to any portion of the design.

Photo-litho transfer paper is in every respect a specific article, the coating of which consists of a gelatinous emulsion, which can be readily sensitised, and upon which a photographic image can be developed. Special preparation and manipulation are therefore necessary in connection with its production, and these points will be fully dealt with in a subsequent chapter.

One more variety of transfer paper should be mentioned, namely, the diaphanic, which possesses excellent qualities for certain classes of work. It is very transparent, and extremely useful in the tracing of key formes, or for making facsimile drawings for immediate transference to stone.

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