(8) The rougher, sharper, and more angular the pores are, the more readily does the color find adhering points. It adheres at first to the surface by virtue of merely mechanical conditions. But when the moisture which hinders a complete union and greater penetration has dried, the color begins to penetrate deeper into the stone and to fill its pores. The most color will always adhere to rough spots. Therefore, it happens often, in some styles of work, that a stone too highly polished will seem perfectly black when inked, and still fail to yield a strong impression. For the same reason the impressions from soft stones usually are the stronger, especially if the mode of printing demands the use of thin printing-color. (9) The effect of the etching fluid is in part a greater polishing of the surface, in part a filling of pores. Both make the stone reluctant to take color. (10) If the stone has been prepared and polished already, it can be made rough again and receptive to color by being reëtched. At the same time the prepared surface can be destroyed by etching, and a communication established with the fat lying in the interior. The result is according to the manipulation. So much in general. In describing the various styles I will make everything clearer. CHAPTER IV THE NECESSARY TOOLS AND APPLIANCES In lithography there is use for many various tools and utensils. I will mention here merely those that are made primarily and exclusively for the art. I CONCERNING STEEL PENS One of the most necessary tools of lithography is the steel pen for writing and drawing on the stone. Simple as its manufacture is in principle, it demands much care and skill. The beauty of the work depends largely on a good and well-cut pen. The best artist, using the best chemical ink on a perfectly prepared plate, cannot do good work unless the pen is good and cut to suit his hand. Therefore it is necessary to learn how to make these pens, because, apart from their costliness, it is difficult to get a suitable one from a worker in steel. The ordinary steel pens that can be bought ready-made from stationers are fairly available for coarser writing and drawing; but for better work one must have much finer pens. Following is the way to make them:--