It should be observed that for this kind of marbling only the darker shade of red is to be taken, as the light carmine lake colour sinks and does not give a fine effect. India red is best of all.
The sprinkled colours are first tested with strips of paper; cuttings of clean note-paper are saved for this purpose. The edges of a book can be marbled only when the book is level or straight, therefore they must be marbled either before rounding or the book already rounded must be levelled by knocking it on a stone or metal slab. In all cases the marbling is done--both with papers and books--by dipping from one corner to the other diagonally opposite, but never deeper than just sufficient to take off the layer of colour. To prevent the colour from getting between the leaves, the edges are held between zinc plates, which must be dried each time after using. To make the paper or edges take the colours more readily and to prevent any subsequent running off, the edges are lightly washed down with alum water. This wash is made by boiling 100 g. of alum in 1/2 litre of water and using it solely for this work.
The alum solution is laid on with a sponge, with which the edges are washed over. The moisture must have thoroughly soaked in, therefore it is necessary to do it 10 minutes before marbling.
If, however, the edges have become thoroughly dry they will take the colours badly. This occurs in from 20 to 30 minutes, according to the temperature. Marbling can only be done in a warm room where the temperature is equable and where there is no dust.
The marbling bath must be of the same temperature as the room. The body must be skimmed each time before sprinkling the colours, but the colours must be sprinkled on immediately afterwards.
An excellent treatise on the work of marbling edges has appeared under the title: [4]_Fortschritte der Marmorirkunst. Von Joseph Halfer. William Leo, Stuttgart._
Footnote 4: The Development of the Art of Marbling.
Gilding edges takes up most time when only occasional books are to be done. The fore-edge can be treated either flat or round. In every case the book must be placed in the press within boards. These boards are narrow strips, about 1/2 cm. thick and up to 5 cm. in width; they must be of equal thickness and bevelled only on long side, the edge itself must be rounded.