Most of the ink produced today is created by a formulation of oils and dies from various sources. Black ink uses carbon black exclusively as a die while different pigments are used to produce all of the different colors of the rainbow that we see in printing today. Resins are added to help bind the pigments together and to help disburse them onto the the specific medium being printed upon.
A major step in the process of producing black ink is wetting the carbon black in a premixing process. Pigment is then added to the oil to create the intended viscosity. Careful attention must be made to obtain optimum dispersion as poor dispersion of the mixer can occur. Optimum viscosity is different for each of the various configurations since each machine will have different mixing and flow capabilities.
Premixing is needed to make sure any air trapped in the ink mixture is displaced. The most common way to premix is by using a high-speed disperser. After the premix runs through the disperser, is is mixed further and additional resin and oil is added to reach the proper milling viscosity or “mill base”. The ink pigment is then run through a chamber to produce smaller particle sizes depending on the degree of dispersion requirements.
From this point, the ink pigment goes through several different steps of filtration to remove any oversized particulates. Because some metal media will be left over from the milling process, an electromagnetic filter is used in order to eliminate these metal fragments.
The next step is to pump the pigment into a “letdown tank” for final adjustments in order to meet the specific requirements of the customer, and then it is ready for shipment.
Color inks are manufactured somewhat differently than blank inks. Rather than dry pigments, flushed pigments are utilized.
In the final stage of the pigment manufacturing process for color pigments, the water-based slurry is filtered and then concentrated into a “presscake” and then mixed with an oil-based varnish. This displaces any extra water from the pigment and allows it to be removed by a heating and vacuuming process.
A major reason for flushing is so that the pigments will be completely dispersed throughout the ink medium. By flushing the pigments, there is also no need for the manufacturer to use energy-intensive milling equipment. However, raw materials such as varnish, oils and extenders must be thoroughly mixed at a constant temperature so that there is no deterioration of the pigments through evaporation.
After this mixing, the ink is run through quality control testing so as to insure that all of the necessary requirements are fulfilled. It is then processed through another series of filtration steps to remove any oversize particles that may have been added through the previous processes. Once this final filtering process is completed, the ink is ready to be shipped to the customer.
Several other manufacturing technologies are also used in the creation of today’s ink, but the steps described here are the most commonly used in the ink industry.
Article written by Erryn Deane from Needham Ink
Erryn is the digital business manager for The Needham Group of companies, with a wealth of knowledge in laser marking systems, amongst many other things, he has decades of experience in online development, business analysis and management. In his spare time, he likes to find out how things work and looks to improve them, from vehicles to electronics or even musical instruments.