Ink for perfecting has special performance requirements. For instance, to avoid smearing after sheet reversal, the ink of the first impression behind the perfector must not build up on the impression cylinders of the following printing units. To achieve this, the ink must be shorter—less viscous or “flowable”—than normal.
Ink manufacturers offer inks especially for perfecting, but if these are not available, the ink can be set short by adding 3% to 5% printing oil. Linseed oil-based additives are particularly recommended because they prevent drying and reduce the ink build-up on the downstream impression cylinders. A short-set ink also reduces trailing of the paper on the blanket.
Sheetfed Offset Press Operating, 3rd Edition
Lean Printing: Pathway to Success
