Technique in cable: the ink is deposited in the cavities obtained by the engraver with the help of one or more acid biting.
The plate is previously granulated. The procedure consists in spreading resinous powders over the plate, with grains more or less thick depending on the desired effect. The plate is heated to facilitate the adhesion of the powders.
The grains of the powders create resistance to the acid, so the subsequent biting (acid bath) will give grainy texture on the plate.
In addition to using powders with grains of different sizes and concentrations, specific backgrounds and effects can be obtained on individual parts of the plate by heating them and subjecting them to different bitings, even with the use of covering paints resistant to acid.
The plate is then cleaned of all dust and paint residues before being inked.
The technique is very effective to achieve chiaroscuro effects, shading and half tones.
It can be combined with etching and other engraving processes.
Color printing is done with multiple plates, usually up to three. With each one you print a color, being careful to obtain by additive synthesis the other colors you want.