A technical dictionary of printmaking, André Béguin.

calcium carbonate..................			97,22
silex.....................................			1,90
alumine................................			0,28
iron oxide............................			0,46
others.................................			0,16

Towards 1920 the Solenhofen quarry began to show signs of depletion but the crisis of lithography saved it from being exhausted. Other quarries in the same neighborhood also provided good quality stones that were appreciated for their ability to soak up water or fatty substances. The French stones came from Chateauroux, Le Vigan, and Perigueux but the grain of these stones was coarser and the colour darker.
The Bavarian stones have two different basic colours: gray and yellow. There are, however, stones which come in closely related colours such as charcoal gray, white, and reddish gray. Below I will discuss how to choose stones in function of their colour.
In recent years an enormous amount of lithographic stones have been thrown away because many lithographic workshops have closed for good. I have even seen little walls built with such stones in the South of France. At present the trend seems to be reversing and as a consequence new workshops are opening and the stones are again being sought after. The stones that can be had often come from old workshops and still bear the traces of previous work; at times this work obviously dates from the 19 th century. In fact, 19th century lithographers often kept their stones for further runs. A well protected stone can be kept for an indefinite amount of time and can periodically print a large amount of impressions if the image is properly protected.
Lithographic printers have a large choice of stone qualities and sizes to chose from. The dimensions may be close to the paper sizes being just a little bigger than the paper to be printed on. In some old workshops one can still find the very large stones that were used to print posters and billboards. The Bavarian stones could be as large as l20x76cm (47x30in) The largest lithographic stone was exhibited in Paris in 1889 and measured 230x150cm (90x59 in) It was a stone that had been quarried at Le Vigan. The prices for the stones sold by the quarries included the planing and polishing of the stone on one side only.
If an artist wishes to work at home (i.e. if he doesn't have his own workshop) he should transport only small or medium sized stones. On the other hand, it is usually better to leave the stones in the printing shop where they wil be kept at a constant temperature. If large format work has to be done it should be carried out in the printing workshop itself. Usually the printing workshops are set up so that there is enough space for several artists to work there simultaneously. Insofar as the corrections and final touches are concerned it is usually easier to work in one of these workshops.
Senefelder was the first to try and make imitation stones as early as 1814. He tried to make such stones for two reasons in particular: in order to reduce costs and to solve the weight problem. In fact, for large format stones several men had to help to lift them about. Senefelder tried to copy the composition of the stones found in the Solenhofen quarry and thus prepared a mixture of calcium and linseed oil to which he added clay and some iron oxyde. Since this mixture did not give satisfactory results he tried another set of ingredients: white lead, lime, and caseine. The mixture was then spread on a heavily varnished sheet of paper. His invention came to be known as paper stone but unfortunately this support did not last for more than a few hundred impressions which, in those days, was insufficient for the commercial uses it aspired to fulfill.
Knecht, Senefelder's nephew, made a more resistant imitation stone using the following ingredients and proportions:

chalk..................			3 parts
silver white.........			1 part
linseed oil............			1 part
lime....................			1 part
iron oxyde.................................			1/8 of a part

It was said that this "stone" could handle some six hundred impressions.
In 1841 Kuhlmann made an artificial stone by boiling chalk tablets in a dissolution cif potasium silicate. In later years experiments were carried out by Von Hertling and Capitaine who mixed dust from old lithographic stones with a solution of coton powder, all of which was added to a mixture of alcohol and ether. The paste obtained by this mixture was then moulded. The next step in the search for imitation stones was to abandon the idea of stone and turn to other substances. Experiments were made with celluloid poured on zinc plates but this and other experiments failed while the use of stones continued.
On the other hand, metal plates, which were also a substitute, began to be used as of 1822 but, as was mentioned earlier, this process will be dealt with separately (see point IV).

2. MATERIALS USED IN READYING THE STONE.
The stones used for lithographic work are quarried at a certain depth. The upper layers, which are two meters deep (six feet) are not suitable for lithographic use because the stone is too soft and absorbant and therefore it is usually used for paving. Below this first layer the stone is cut into blocks, each block being made up of several layers that can be anywhere from three to twelve centimeters thick (1.2 to 4.8in). The layers must then be separated from each other but the job must be done very carefully as it is a delicate task. The next step, which is carried out in the quarry, is a first shaping of the stone which is chiseled into approximate sizes and cut into the proper shape. Usually the quarries also carry out the next step which is to clean the two surfaces of the stone and make them parallel to each other. This step can be done manually, stone against stone, much in the same way as the pumicing described below is done. At this stage, however, the work is generally done with machines in which case the stone is fixed onto a cart. The stone is then rubbed with two plates set in with metal blades. The blades turn on their own axis while the plate girates thus achieving two separate movements. The stones are delivered with only one side polished unless special conditions are requested. This procedure, described above, is currently followed by the few German quarries that have opened again.
Although the printer receives his stones ready for use he still has to carry out further preparations according to the use he intends to make of the stone. In fact, he may have tp grain it or polish it further. Another job done by printers is the recycling of used stones. Stones that have already been used must be cleaned so that none of the previous image remains. Only then may a new image be drawn.
This cleaning is done on a special table which must be very large and solidly built so that it can carry even the heaviest stones. The stones worked on this table must be no bigger than the table top. The table is built with an opening in its surface below which there is a kind of cone lined with zinc or lead. This cone collects the water and mud that run off the stone while it is being pumiced and drains them through a little hole in the bottom. The sizes of these tables are usually 135x100 cm (52 x 39 in), l00x85cm (39x35in), and l00x75cm (39x29in).
The pumicing, graining, and polishing of stones is done with various abrasives including sand from river beds, sandstone, or powdered carborundum. A sieve is needed to sift the abrasive to the same size. If the abrasive must he crushed a graining disk wIll he. used on the stone surface . A graining disk is a rounded block of cast iron whose surface (the one in contact with the stone) is either smooth or full of little holes. These holes prevent the disk from sticking to the stone surface. There is an off-center handle on the disk which turns on its own axis and causes the disk to rotate. The handle is meant to be held with the right hand while an increasingly fine abrasive is powdered onto the stone with the left hand. The work is then finished off with a sandstone brick with holes in it (the holes facilitate the evacuation of sludge and air, both of which can cause the brick to stick to the stone). Other types of bricks are also used, such as those made with pumice stone dust. Sealing-wax bricks are made with pumice stone dust of varying degrees of fineness mixed with alum and wax. They are used for polishing and finishing stones (see below and under graining and polishing).
When industrial lithography was still practiced a variety of machines were sold that carried out the various steps described above: there were machines for levelling the stones, for pumicing, for graining, and for removing previous images. A more detailed description of these machines willl be found in the article devoted to machines in general [machine].
The big workshops of the past also had two-wheeled wagons with which the large stones were moved around. These wagons were needed because the stones could weigh as much as one thousand kilos (2,200 pounds) and because they had to be moved about from the pumicing area to the drawing area, from