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.
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.
A bowl, about 6 cm. across the top, is kept for each colour, and also a hog's-hair brush and a birch-twig brush.
A small bundle of birch twigs is tied round with thread, leaving about 4 cm. of the twigs free, the thickness of the lowest part tied not exceeding 1 cm. The bristles of the brush are tied back so as to form loops and held awhile in boiling water so that they retain their shape after drying and untying. With a brush made up in this way, drops may be laid on anywhere.
For all drawn-out edges only bristle brushes are used, whilst for all other edges a brush is used only for laying on the first colour. For some edges a wide brush is used, so that the whole trough can be filled at one blow; a carpet brush with a short handle is most convenient to use.