1831.] 
Limestone to Lithographic purposes. 
109 
Traces of magnesia were carefully sought for, but without success. 
The above analysis is sufficient to show, that our Indian stone, though not an ar- 
gillaceous limestone, which is the proper character of the best lithographic stones, 
has yet, in its freedom from magnesia, a claim on our attention. This freedom 
from magnesia, with the peculiarity of its grain, fit it for every ordinary sort of 
work, and except in the chalk department, it will be found a very useful material 
to the Indian lithographer. 
In preparing the Jaisalmir stone for use, no variation takes place in the usual 
process observed in lithography. The chemical and printing inks, the transfer 
paper, and other parts of the manipulation, are the same as when using the German 
stone. There is, however, one exception which requires careful observation, for on 
it depends the success of the whole operation. The sleek stone and pumice, 
generally used in polishing the German stone, will not bring the Jysalmir material 
to that high degree of polish, absolutely requisite for a surface on which transfer 
is to be made. Unless the Jaisalmir stone be brought to a high pitch of polish, 
good impressions are not to be expected from it. As this part of the process differs 
widely from the usual practice, it will be here minutely detailed, commencing at the 
point when a rough trimmed slab is supposed to be laid out for the purpose of grind- 
ing and polishing; the lithographer, in practice, will, however, only be concerned 
with the latter ; the former being the work of the lapidary, and only requisite 
when the slabs are first brought from the quarry. 
Method of Grinding and Polishing the Jaisalmir Stone. 
The slab of Jaisalmir stone to be polished, after the inequalities have been removed 
by the common stone-cutter’s tool called the point , is brought to a general level, 
by chiselling furrows across it, in a direction parallel to its sides, about 1£ inch 
apart, so that the surface, in this state, has a chequered appearance ; the intervals or 
squares formed by the furrows being somewhat raised : these are reduced after- 
wards, to the level of the furrows, and the stone is now ready for the operation of 
grinding,which may be divided into three separate heads : — 1st, the rough grinding j 
2nd, the smoothing ; and 3rd, the polishing. 
The rough grinding is performed with a gritstone rubber, and the surface of the 
stone is, during the operation, kept constantly wet. The larger the surface of the 
rubber, the more perfectly will the surface of the slab be reduced ; this operation 
is continued until all the marks of the chisel have entirely disappeared. Then the 
smoothing is commenced, with rubbers made of common lac and corundum, 
generally of three kinds : viz, coarse, medium, and fine. The method of preparing 
these will be described hereafter. Their application is similar in all respects to 
that of the gritstone rubber ; the surface of the slab being kept constantly wet. 
It must be observed however, that no one rubber is to be changed for a finer one, 
until it has entirely effaced the scratches made by the one used immediately before 
it, which may be easily ascertained by observing whether the surface of the slab 
appears uniform all over ; for as the marks made by the coarse rubbers will be lar- 
ger than those of the finer ones, their presence on the surface will be readily detect- 
ed. The operation of the fine rubber must be continued until the surface 
assumes a glossy or pearly appearance, when it is nearly ready for polishing. Should 
any scratches appear, they must be removed, by using the coarse corundum rubber 
again ; and until this be effected, a perfect polish can never be given. 
The last operation, that of polishing, is performed with calcined tin, (the peroxide,) 
a small quantity of which is laid upon the surface of the slab, and a few drops of 
water are added. This is to be well rubbed in with a pad made of 4 or 5 folds of 
fine calico, renewing the calcined tin, and adding, occasionally, a few drops of 
