The white dots are caused by speaking during the work, and thus dropping spittle on the plate. If the spittle is mucous, the plate covers itself there with a fine crust that resists the chemical crayon so that it does not soak into the stone and is wiped away by the inking-in. If the spittle is fatty,--for instance, if one has eaten anything greasy,--the dots that appear will be black. The same results from touching the plate with fatty hands. Sometimes a whole picture of the fingers and skin will appear on the impression. Let us suppose that after inking-in, a plate shows all these faults: the finest shadings vanished entirely, the darker places run together, white and black dots and smut-marks so that the plate has become useless in every respect. Can this be remedied? If so, how? I answer that it can be remedied in every point; but that the artist himself must decide if it will not pay better to do the whole design anew. The second question I answer as follows:-- Before everything else, it is necessary to remove all that should not be on the stone, all smut-marks and black dots; and where the design has darkened, white points or lights must be graved-in. To accomplish this, the stone is inked-in first with a firm acid-proof color, and over this with a lighter one. Then erase or grind away the dirt that is outside of the design and that would dirty the margin of the printing-paper. No erasing or grinding must be done within the design itself because then the grain would be destroyed and the necessary drawing could not be done as it should be. Therefore the faulty parts must be removed by engraving, with a more or less sharp needle of good steel, so that what remains looks quite like a good grain. A little practice will show that this work is not at all difficult and can be done quickly. Places that have run together can be cleared and made transparent and clean in a few minutes. If certain points have become too large, they can be corrected by engraving a white point in their centre or by engraving a line through them. Here I must note that parts of crayon designs thicken sometimes because the crayon has slipped in drawing, without leaving traces perceptible at the time. If the etching is weak, it may happen easily that this place takes printing-color. Skillful engraving may not only correct the defect, but actually gives the design a beautiful tone and power such as cannot be easily produced by the crayon itself.