They can be stored anywhere that is not too damp and not too much exposed to winter cold. Dry cold does not hurt them; but if they are wet through and through and then freeze, they will crack. In constant dampness, too, saltpetre and other salts enter them and they crumble. In clean water they do not undergo any changes. I will describe the storage of etched and designed stones later. If the stones are to be used after being stored in any damp place, they should be kept for several days in a temperate and dry place till they have dried thoroughly, as otherwise they are not easy to work in any style. This is not necessary if their place of storage has been perfectly dry. CHAPTER II OF INK, CRAYON, ETCHING, AND COLOR I CHEMICAL INK The first and most necessary material in a stone printery is the so-called chemical ink, which would better be named fatty or alkaline ink, since it is a mixture of fatty and resinous materials with alkali. It is used partly to write or draw directly on the stone, partly to cover the stone as with an etching surface, and partly to transfer to the stone from paper. The purpose of this ink is, first, to cause a mass of oily, fatty substances to soak into the pores of the stone and also make certain portions of its surface fatty; and secondly, to resist acids according to requirement in such degree that the stone shall remain fat where needed, that thus the design, applied with this ink, shall be left untouched by acid. I have remarked before that countless different mixtures can be made, most of which fulfill the purpose. But there enters the consideration that it must be an ink easy to use, that handsome work may be done by the artists with perfect ease. Various mixtures answer this purpose very well, and I have found sometimes that men could work better with mixtures made by themselves than they could with those that I used for my own work. Perhaps this was a matter of imagination, or the real reason lay in the pen-cutting, it being well known that one man can use a pen that is absolutely worthless for another. I myself have tested the values of some mixtures so thoroughly that I can declare almost positively that it will not be easy to find better ones for any purposes. I will describe these fully. First of all, stone-ink is divided into two great classes. One is thicker, being used for drawing on stone. The other is more fluid, being used for transfers. The following mixtures of the first kind are the best:-- (1) White Wax 8 parts Soap 2 parts Lampblack 1 part This ink does not really serve for writing or drawing on the stone, but is used mostly for coating those places that are to be protected from the etching fluid. If this ink is needed in a thickened form, the wax should be heated in an iron pan till it burns and the combustion should continue till one half of it is consumed. The longer it burns, the harder will be the remnant.