The book must be pressed for pasting the edges, and the paste colour must not be laid on too thickly or it will spring off when dry.
Coloured as well as paste edges will take gold tooling and afford considerable scope to the skilful and thoughtful workman.
The finest way of finishing edges and the one allowing greatest variety of treatment is known as marbling; this is a special process.
Formerly regarded as a secret art, it is now an easily acquired branch of our work, thanks to the careful experiments and excellent demonstrations of the master bookbinder, Herr Joseph Halfer, of Buda Pesth.
The whole process of marbling depends upon the peculiarity possessed by colours of floating upon a sized surface when they are mixed with oxgall, and a colour containing more gall forcing off the one first applied. Besides, the colours may be drawn about with a pencil or stick without their mixing. If the smooth edges of a book are brought into contact with such a floating surface-colour they will take up the colours completely.
Ground and colour must each have certain fixed degrees of consistency, and the atmosphere both in and out of doors has also a great influence upon the work.
The prepared body, shortly known as "the body," is at present always composed of boiled Carrageen moss. To every litre[3] of water exactly 12 g. are added and the liquid is put in a saucepan, which is never used for any other purpose, and placed on the fire, great care being taken to catch it just at boiling point or it will all boil over. At the right moment take the saucepan from the fire and strain the contents through a hair sieve, what remains being thrown away as useless. The body may be used the next day, but for figured edges it is better after having been kept three days, and for veined marbling five days. The vessel containing the body must be kept covered so as to exclude all dust.
[3] Not quite a quart.
Gum tragacanth (known as "gum dragon") can also be used as a body, but Halfer's colours are not intended to be used with this.
A marbling trough to contain the body is used whilst working; it is made of zinc plate, is about 15 cm. in width, 50 cm. in length, and 3 cm. in depth, and has a sloping partition soldered near one end, and the colour not taken up is drawn into the division thus made.