This section will be devoted to the grinding of colored pigments in oil for the use of the painter and decorator, the artist, and for the various industries requiring such material, as well as for use in tinting ready-mixed paints, incidentally touching on printing and lithographing inks. At the same time the preparation and grinding of quick-drying colors, known as japan colors or coach colors, will be treated, suggesting the proper vehicle for each pigment, whether it be coach grinders' japan, japan gold size, varnish, etc., and how they are best tempered for certain special purposes. Colors ground in water without size (so-called distemper colors) and graining colors will also come in for a share, as well as tinted paste paints. To facilitate reference as to certain colors, each pigment is treated by itself, whether it be ground in oil, japan, varnish, water or any other vehicle, and the pigments will be taken up in alphabetical order, under separate headings, such as blacks, blues, browns, etc., etc. Under these headings each pigment belonging to the class will be dealt with, giving a short description of its nature, tests for value, how to select and treatment in mixing and grinding and nature of vehicle best suited for same, as well as the average percentages of pigment and oil or other vehicle required. A few remarks bearing on apparatus will not be amiss. No matter what the nature of the pigment may be, a thorough mixing is most beneficial, because it facilitates grinding; but permitting a mixer to run until it becomes heated is disastrous, especially in instances where the vehicle is japan or varnish, because it tends to render the mixing gummy on account of the evaporation of the volatile portion of the vehicle. Nor is it good practice to add the pigment too rapidly to the vehicle in the mixer, for the reason that it not only produces imperfectly mixed material, but requires excessive power, which is wasteful expense. This is also true of the mills in grinding the colors in no matter what the vehicle may be, but, of course, more so, in the case of japan or varnish colors. Every mill should be well balanced and the grinding surface of the stones frequently dressed (i. e. made sharp) and given low breasts, so that the material can pass freely from the feeding eye of the mill to the grinding surface, otherwise it will not only gum up the material or make it ropy, but will waste motive power. The speed at which the mills should be run depends, of course, very much upon the diameter of the mill stones, but also upon the nature of the material. We shall consider this for the various colors as we go along, but may say that in the case of soft pigments, such as, for instance, lampblack, will yield a larger output per mill and per hour when the mill stones are of the Esopus (soft) variety than could be had if they were French buhr. The latter, however, are really necessary in the grinding of hard, gritty material, as in this case the material would be more apt to grind the surface of the stones, rather than the opposite. Years ago, the ideas of the practical color grinders as to fine grinding of oil colors, as well as coach colors, leaned toward limited diameters for the mills, and in some large plants may be found even to-day rows of iron mills of eight-inch diameter, though they are disappearing very fast and even mills of fifteen-inch diameter are being thought too small in diameter for some of the managers of paint factories of the present day. Mills of twenty-inch diameter are preferred, and, when kept in good running balance and well dressed with proper grinding surface, colors in oil or japan may be ground out as fine as on a mill of eight or twelve inch diameter. But it is not every color grinder that has a large enough demand to run a sufficient quantity through a twenty-inch mill, and it would not pay him to use that size mill for a small quantity. Therefore, the original twelve-inch or fifteen-inch water-cooled stone mill is best adapted for the purpose. For grinding large batches of colors of light gravity in oil, such as lampblack, dropblack, etc., twenty-four-inch or even thirty-inch mills may be used to advantage, while for those of heavier gravity, such as mineral browns and reds, ochers, chrome greens, mills of twenty or twenty-four inch diameter are better adapted. Chinese or Prussian blues, raw and burnt sienna, raw and burnt umber and chemically pure greens - in fact, any color that is apt to be thrown from the flange of the running stone should be put through mills of not over twenty-inch diameter, same to be provided with a metal pan that is fastened to the legs of the mill frame and makes a gutter, catching the drippings from the flange of the lower stone, to which is fastened a scraper that cleans the gutter of color, discharging it through a gateway into the container provided for the purpose. That there is a very decided saving in the adoption of this plan should be very evident to the practical color grinder.