As the success of marbling depends upon the quickness with which it is executed, it is important that the colours, sponges, brushes, and water, should be previously disposed in order and at hand, so that either of them can be taken up instantly. Another point to which attention must be directed is the amount of colour to be thrown on, and consequently the amount that each brush should contain. If too much colour (black) is thrown on, the result will be invisible; if too little, no matter how nicely the marble is formed, it will be weak and feeble.
Marbling on leather is produced by small drops of colouring liquids, drawn (by flowing water down an inclined plane) into veins, and spread into fantastic forms resembling foliage - hence, often called "tree-marble." It requires great dexterity of hand and perfect coolness and decision, as the least hurry or want of judgment will ruin the most elaborate preparation.
To prepare the book, paste-wash it evenly all over, and, to further equalise the paste-water, pass the palm of the hand over the board after washing it. When dry, wash over with a solution of oxalic acid 2 or 3 times to get the desired tint. When dry, glaire the whole as even as possible, and to diminish the froth that the sponge may occasion, put a few drops of milk into the glaire. Again, allow it to dry thoroughly. Put some fresh copperas into a pan, and some solution of oxalic acid into another, and soak each brush in its liquid. Place the book upon the rods, the boards extending over and the book hanging between. Should it be desired to let the marble run from back to foredge, the back must be elevated a little, and the rods supporting the boards must be level from end to end. The elevation must be very slight, or the water will run off too quickly.
Place a pail of water close at hand; in it a sponge for washing off, and a bunch of birch to throw the water with. A little soda should be added to soften the water. Charge each brush well, and knock out the superfluous colour until a fine spray comes from it. A little oil put on the palm of the hand, and the brush well rubbed into it, will greatly assist the flow of colour from the brush, and prevent the black colour from frothing. Throw some water over the cover in blotches with the birch, just sufficient to make them unite and flow downwards together. Now sprinkle some black by beating the brush on a press pin, evenly and finely. When sufficient has been thrown on, beat the brown in like manner over the extended boards. When the veins are well struck into the leather, sponge the whole well with clean water. Have no fear in doing this, as it will not wash off. Then set the book up to dry.
The cover is prepared and sprinkled in the same manner as in marbling; the boards, however, must be bent a little, and water applied by a sponge in the centre of each to give the necessary flow; when the water is thrown on, it will flow towards the centre or lowest part of the boards, and when the sprinkle is thrown on, a "tree," as it were, will be formed. The centre, being white, forms the stem, and from it branches will be formed by the gradual flow of the streams of water as they run down.
For marbling, everything must be ready at hand before any water is thrown on, so that the water may not have time to run off before the colour is applied. The water must run at the same time that the spray is falling, or a failure will be the result.