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.