Moreover, proof impressions of the different colors must be taken upon white cardboard, which should be marked for reference, in the same way noting the proportion of the colors used in mixed colors. If the outline block is to be printed in color it comes last; gold stamping being done first.

The process of printing in bronze is similar to color printing, as the bronze is dusted over a preliminary impression in color (gold upon red or yellow ochre, aluminum upon white, colored bronze upon a suitable similar color). Bronze is not printed upon color, because the bronze sticks too easily to such surfaces in places where it is not wanted it is then much better to use gold-leaf.

Should it be necessary on the score of economy to make a double working in bronze, the cover must be previously washed with glair.

Leaf metals, pure or alloyed, are printed upon colors after they have been slightly dusted with gilding powder, and with moderate heat. The colors, however, must previously be allowed to dry thoroughly. Larger surfaces are wholly prepared with glair to prevent the gold from adhering where not required.

Most of the colors must cover well where it is not intended that they should have a translucent effect. A good covering is not secured by laying the color on thickly but by properly mixing the colors, and often also by giving a second coat after the first surface has dried. Above all, one must avoid too thick and greasy colors. Black must always be printed with a strong good covering color, as must also the outline block.

For color printing, the press must be of the same temperature as the room. In winter it is slightly warmed an hour before use, and when necessary this must be repeated later.

There are quite a number of little dodges not easily communicated but which are quickly picked up in practice. Simple work is not adjusted by pins, but is pushed up to three guides; moreover, the gauge of the press is not generally used, but three little pieces of board are firmly glued to the table instead. The illustration (Fig. 67) will clearly show the arrangement. At the letters A the pieces of board are glued, to which the cover to be blocked is pushed up.

< Working with Blocking Press Part 8