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.
CHAPTER II
Lithographic Transfer Inks
Various Forms—Distinguishing Features—Formulæ—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.