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.
[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.
Many makers send out boards bevelled right from one side to the other. This kind is very unsuitable and has many disadvantages. The boards must not be made from wood of very open grain, and firs and oaks must not be used. The boards are to be somewhat longer than the edge about to be treated, so that the edge may be as firm and tight as possible and at the same time easy to work upon; two outer boards are added to those regularly used, as shown in Figs. 49 and 50.
The inner boards are quite flush with the book: the latter must on no account stand back. The outer boards are about 3 mm. behind the others; the book is so placed in the press, and here again the book and boards must be exactly level with the press cheeks. The press is then screwed up as tight as possible. If the inner boards have not perfectly straight edges they must be planed down.
