TABLE OF CONTENTS The formulations in Chapter 13 contained ingredients used in the manufacture of printing inks which fall into three categories:
Liquids such as vehicles
Solids such as pigments
Supplementary additives such as driers
The raw materials (Leach and Pierce, 1988),chemical description, and sources of materials are provided in Table 14.1.
The vehicle acts as a carrier for the pigment and as a binder to affix the pigment to the printed surface. The nature of the vehicle determines in large measure the tack and flow characteristics of a finished ink.
Inks printed on soft absorbent papers, such as news and comics inks, dry by the absorption of the vehicle into the paper. The vehicle consists of nondrying, penetrating oils such as petroleum oils, rosin oils, and others, used in combination or modified with various resins to impart suitable tack and flow characteristics.
Autoxidation drying is the type used in most letterpress and offset inks today. It also plays an important role in other types of drying processes by imparting final, thoroughly hard drying after the inks have been initially "set."
Autoxidation generally proceeds in two stages: the absorption of oxygen from air, and the cross-linking or hardening of the vehicle. Only the second stage produces a physical change and development of a hardened film.
Drying oils include, but are not limited to, the following:
Linseed oil
Cottonseed oil
China wood oil
Castor oil
Perilla oil
Soybean oil
Petroleum drying oils
