Therefore, if it is desired to produce clean and lustrous edges in which the white lines appear without a trace of color, then this advice is to be followed, the small trouble being amply repaid by the beauty of the edges. Ordinary earth and several of the lake-colors take without wetting of edges with alum water, but these colors leave much to be desired in their divisibility and fineness and always appear rugged. A much finer fixing medium is the acetate of aluminium which can be easily produced. Dissolve 1 pound of alum in 3 quarts of warm water, prepare another solution with the same quantity of soda, mix these two, whereupon the hydrate of aluminium is precipitated. Allow the latter to settle, pour the water above carefully off, and filter; the white body which remains consists of hydrate of aluminium which is readily dissolved by a little acetic acid, into a clear fluid and can be diluted with the same volume of water. Then heat the whole liquid, when the excess of acetic acid is evaporated, we have the desired acetate of aluminium which can be used in the same way as alum water. Edges and paper which are to be marbled should only be moistened with alum water or aluminium acetate shortly before the marbling and should stand not longer than a half-hour after the sizing of the edges, because later on, an insoluble layer is formed which only takes color with great difficulty. It is therefore best to prepare the colors before commencing the sizing of the edges. If there are a large number of books, it is better to divide them into two or three lots. The Preparation of the Colors for Marbling. THE PREPARATION OF THE COLORS FOR MARBLING. The want of knowledge of colors gave me the greatest trouble when I began their manufacture as I had no information as to why this or that color was unfit for marbling. The numberless experiments I made to this end remained without results. It was an exceedingly great trial to my patience, but by the pertinacity with which I clung to my investigations, I, at last, succeeded in making the important discovery, that the real value of color for marbling purposes is its body and that the color itself, which is bound to the body either naturally or chemically, is of less importance. By this discovery every difficulty that I had so long experienced was cleared away and it was made manifest, why it had been impossible for the marbling art to become sufficiently popular. From this time on I had a foundation, upon which to continue my investigations with greater surety. Finally I succeeded in finding that the colors named later on are good and useful marbling colors.