From this it will be seen that the colors, to be useful for our purposes, must be thoroughly insoluble. The gall is added during the process of grinding the color, so that the particles of colors are fully surrounded by the gall. The gall has an excellent effect on the colors but it also can act very injuriously if the necessary precautions are not taken. Carelessness is mostly the reason that the edges do not possess the demanded lustre of color and why they appear pale, as the marbler often uses the gall too soon when he notices the smallest obstacle, (due in most cases to the size.) It is therefore not astonishing that brilliant comb or peacock-edges are so rarely seen. It is an obstacle to marbling, that the gall mixes so easily with the size. It often happens that the gall spoils the size before an edge was ever produced on it. This happens especially when the size on which the colors are prepared according to the old method, is too thick. The size is frequently soiled and spoiled when the colors are prepared, because the colors can not be perfectly drawn off on thick size. There will always remain some particles which will not only soil the size but impregnate it with gall, and which will cause the entire uselessness of size and color. A very consistent size will make the preparation of colors extremely difficult, as they need a double quantity of gall for the purpose of spreading out. If there is but one color used, the preparation on such a size would be possible without spoiling it, but with four colors this is entirely impossible because the repeated drawing off of the colors, which always leaves particles behind, will, by and by, impregnate the size so that when the fourth color is prepared the first will not spread out any further. The more the impregnation of the gall and size increases, the power of expansion of the colors decreases and this continues until both materials are useless. It is therefore advisable, as I have already stated, in the chapter upon the varieties of sizes that the colors should be prepared separately on a small part of size to determine the correct consistency of the latter and to prohibit the whole size being soiled. The gall should be kept in a small bottle containing about 1/10 quart with a perforated stopper from which a small tube protrudes and from which the gall can be added to the colors in drops. Although the preparation of the color in this way takes more time, this trouble is amply repaid by the result. Fatty bodies are injurious to the size, therefore they must be carefully avoided because they have the same effect as the gall, they form, although not insoluble in water, a combination with the size and prohibit the colors from spreading out. Fatty bodies can be transferred by glutinous fluids into a state of the most minute division and they then form emulsions.