Printing Ink is a complex mixture of ingredients that are combined in a specific formulation to meet desired characteristics of the printing application of the ink. Ingredients in no-heat inks fall into four major classifications: Pigments, Resins, Oils or Carriers, and Additives.
The function of the pigment is to provide the coloristic properties of the ink. The resin is added as a dispersion aid and also as a binder to affix the pigment to the paper. The oil or carrier is the medium for transferring the pigment and resin through the press to the paper. Additives are used in no-heat inks to control pigment wetting and dispersion, viscosity and flow characteristics, as well as to provide a proper ink/water balance.
The pigment used in news ink blacks is pigment carbon black. Carbon black is produced by cracking oil in a continuous furnace. These furnaces are highly controlled in order to produce a specific grade of pigment varying in particle size and structure. The oil used is also of a specific grade so that certain requirements can be met. The ink film thickness applied by the printing application dictates the concentration of pigment needed to meet the required print density. The web offset ink has a higher concentration of pigment than that of the letterpress. This is because the letterpress printing process applies a much thicker film of ink than web offset.
Carbon black is the dry pigment that is predominantly used for black news ink manufacturing. Different grades of carbon black are selected for different types of news ink: Letterpress, Web Offset, and Aqueous. The manufacturing goal is to disperse the pigment in a vehicle that can transport the pigment to the paper. For black news inks, the primary carriers are petroleum oil, soy bean oil, or water (for the flexographic printing process). Resins are also introduced to help disperse the pigment and to bind the pigment to the paper after printing.
During the initial manufacturing phase, the carbon black is dry and packed together, forming "aggregates" and "agglomerates" of pigment particles. Dispersion is the process of breaking-up or reducing the aggregates and agglomerates to a desired particle size.
One of the main steps of the manufacturing process is wetting of the carbon black by the vehicle. This means displacing the occluded (trapped) air and covering the surface of the agglomerates completely with the vehicle. This is accomplished in the step called premixing.