Once the varnish (containing the solvent, resin and additives) has been produced the pigment is mixed into it. At this point the pigment particles clump together. These clumps must be broken up and the pigment dispersed evenly through the resin. There are three main types of equipment used to do this, and which is chosen depends on the tack (stickiness) and rheology of the ink. The three equipment types are discussed below.