The beginner will be well advised always to use one and the same quality of paper until he has succeeded in attaining full command of the printing technique; I have already pointed out that papers of different surfaces take the ink from the bromoils with different degrees of ease or difficulty. Similar differences also occur with increase of pressure. When the operator has once become perfectly familiar with the necessary adjustments of pressure with one sort of paper, he will be able without difficulty to estimate the degree of pressure for other papers. At the start it is advisable to use a good, half-sized moderately rough drawing or water-color paper.
It may be remarked that transfers may be made on silk or other textile fabrics as well as on paper. If permanent results are desired, care must be taken that pure fabrics are chosen, that is, such as are not filled, as is usually the case with silk. As the fillers are usually metallic salts, they may easily have a destructive chemical effect on the inks.
The Machine.—In order to obtain a good transfer, a machine is required which must satisfy to the fullest extent two requirements: the pressure on the rolls must be capable of being regulated at will before and during the printing, and one must be in a position to examine the condition of the print at any time, without danger that the bromoil print and the transfer paper will shift. By pressure on the rolls is meant the distance between the two cylinder surfaces.
Fig. 1
The autographic metal hand press, model A, as supplied by the firm of Hugo Carmine, Vienna VII, at comparatively reasonable prices with different lengths of rolls, is almost an ideal machine for our purpose. It is shown in Fig. 1 and consists, as will be seen, of a massive metal stand, which may easily be screwed to any table. Through the center goes the lower roll or printing cylinder, which is prepared of an elastic material, and this stands at the same height as the two tables seen on both sides. Above this lower, immovable roll, there is the upper one, which can be set higher or lower as required by the central spindle, in the center of which is the wheel. The central spindle is so arranged that the upper roll can be raised or lowered by screw gears at the right and left, the arrangement being such that absolutely even pressure is exerted at the two ends. On the right screw gear there is a notch in the form of an I, which with every half revolution of the central spindle moves the length of one tooth forwards or backwards, according to the direction chosen, so that it is always possible to produce an absolutely determinable pressure. The rolls, after the setting of the pressure, are rotated by the handle visible on the right.
This is the whole machine. Its dimensions are determined by the length of the rolls, and these are chosen as may be needed. One with 40 cm (16 in.) rolls ought to be sufficient for most work.
It may be possible to rig up existing burnishers or washing mangles. Whether good results can be obtained therewith, I cannot say from my own experience.
The care of the machine is very simple; it needs only to be oiled from time to time.