For precaution's sake let me here repeat the description of the preparation of colors: before using them shake well and then pour into the different small vessels as much of the same as is necessary for one marbling operation only, then put them away handy for use in the following order, black, blue, yellow and red. Black is used for shading all other colors, therefore, it should be thrown on first as the ground color. As I mentioned before, the colors are to be prepared upon a small surface of size so that the whole size may not be soiled, as it is nearly unavoidable during the preparation to prevent several drops from sinking. Whether the colors are suitable to each other as regards their expanding power or whether the size is too thick or too thin for comb-marble is determined in the following manner; draw off the size in a dish, by a strip of paper, throw on a drop of black, which if size and color are correctly proportioned must expand to a spot of 4 inches in diameter. If the drop does not expand in this way the size is either too thick or more gall must be added to the color. Add from 5 to 10 drops of gall to the black color and repeat the experiment. If then the color does not expand to the given diameter take a stylus and draw it in wavy lines such as used for comb-marble. If the color can be drawn into beautiful straight lines, without following the stylus, the size possesses the normal consistency and more gall must be added to the color, until it reaches the aforementioned diameter, but if the color is drawn along by the stylus or cannot be easily cut by it, then the size is too thick and must be carefully diluted with water. If, on the other hand, the color in drawing with the stylus should run, then the size is too thin. This can also be easily seen by the extraordinary quivering of the size. Such a size cannot be used for comb-marble, either you must add some thick size or you must use it for common marble edges. The black color is the key to the success of a beautiful edge; the other colors must be prepared according to the strength of the black.
When the ground color has spread out to the desired dimension, throw on the black a drop of blue, then yellow on the blue and red on the yellow which must all expand to a diameter of 1-1/2 inches. Should this not be the case then several drops of gall are to be added in the order aforesaid. The three latter colors must be prepared by themselves, and if, after throwing a drop of blue on the black, the former does not reach the necessary expansion, gall must be added in drops until this is achieved, then the yellow is manipulated in the same way.
When all colors are toned in regard to their power of expansion, then and not before then, can the marbling commence.
With a little experience or practice the whole manipulation is finished in less time than it takes to describe it.
Pour the size into the trough, take the top of it off with a thin piece of wood which fits into the trough closely, smooth it over with the wood so that the surface is free of bubbles, then throw on, by the aid of a hair brush, the black in the direction of the length of the trough towards the centre of the size in such a way that the first drop comes in contact with the rim of the second, the second with that of the third, the third with the fourth, etc., so that a ribbon from 4 to 5 inches wide is formed. Then throw on the blue in drops at both sides of the black following the length of the trough, but the joining of the drops must be avoided. Yellow is thrown on at both rims of the black just as the blue was but in such a way that each drop of blue has a yellow centre. Finally red is thrown on the yellow so that each drop of yellow receives a red centre. By this means we produce a beautiful combination of colors. Then take a thick knitting needle or a thin stylus of wood and draw the colors in wavy lines through each other but so that the stylus will pass the boundary of the black. By doing this white lines will be produced between the colors, adding at the same time, the fifth color white which causes the marble to attain a brighter aspect. If then the comb is drawn across, beautiful scales will be produced.
The books which have been wetted shortly before with alum water, are now placed between boards or clamps and are dipped from right to left, somewhat obliquely, into the trough so that the left end of the book touches the size first, and then with a firm hand the book is inserted towards the right until the right end has touched the size. This must be quickly done to avoid the formation of air bubbles. As soon as the marble edge is taken off, the superfluous size is carefully removed from the edge by a moist, soft sponge so as to prohibit moisture from penetrating too much into the leaves of the book. In this operation great care must be exercised to prevent the marble edge being rubbed out or spoiled.
The remainder of the color is to be taken off the size by the aid of strips of paper and this is done in the following way: one strip is inserted into the size at the left end of the trough in such a way that it slightly enters the size, then by the aid of a second strip of paper, the top of the color is taken off beginning at the right end of the trough and moving the film to the left till it is brought between the two strips of paper and can be removed from the trough into a basin which is kept ready, to receive the waste color. If the colors are quickly removed in this way, the size itself remains perfectly clean even though a large number of books be treated.
On good work, the book at first is only cut in front. As soon as the front edge is marbled and dry the book is backed, and cut at the top and bottom; both edges are wetted with alum water and again the colors are thrown upon the size taking care, that the scales of the upper edge run in the same direction towards the fore-edge as those of the lower one. In more common bindings, all three sides are cut together and after the front edge is marbled and the book is rounded and backed, the marbling of the upper and lower edges is executed without delay.
The rounding of the book must be done before the marbling of the upper and lower edges, because the comb would become disarranged, if the rounding were executed afterwards. Remember that always before throwing on the colors, the top of the size must be taken off by the aid of the piece of board, as, by evaporation, a film is formed over the surface which does not permit the expanding of the colors. The quicker the marbling is executed, so much more beautiful will be the edges.