High-Quality Water-Based Flexographic Inks for Consistent Printing

Flexographic printing inks are complex mixtures whose performance is critical to the economic and qualitative success of the printing operation. A fundamental property is viscosity, which affects every stage of the printing process. It is typically measured with a cup viscometer (e.g., Zahn cup) or more precisely with a rotational viscometer. In water-based inks, viscosity is often controlled by the addition of water or amines; in solvent-based inks, by the addition of solvent. Automated viscosity controllers are increasingly common on press to maintain this parameter within a tight window, ensuring consistent ink transfer and color density. The pH of water-based inks is another vital parameter. Most water-based flexo inks are mildly alkaline (pH ~8.5-9.5) to keep the acrylic resins in solution. A drop in pH can cause the resin to precipitate, leading to a dramatic increase in viscosity, loss of gloss, and poor water resistance. pH can be adjusted with amines like ammonia or AMP-95. The phenomenon of foaming is a common issue in water-based inks, exacerbated by pumping and circulation. Foam can cause print defects like pinholes and, in severe cases, can overflow the ink pan. Defoamers are added to combat this, but they must be chosen carefully to avoid causing other problems like cratering or reduced wetting. A specific application that tests the limits of flexo ink technology is printing on release liners for pressure-sensitive labels. The silicone-coated surface is extremely low energy, making adhesion very difficult. Specialized inks are required, often based on unique resin systems that can chemically bond or mechanically key into the silicone surface. These inks must also be compatible with the adhesive that will be applied later and must not inhibit the release properties of the liner. In the context of global trade, ink stability during shipping and storage is important. Inks may be subjected to extreme temperatures, which can affect viscosity, cause settling, or lead to gelling. Robust packaging and formulated stability over a wide temperature range are essential qualities for an ink supplied to international markets. For assistance with press-side ink management, troubleshooting common issues like foaming, pH drift, or adhesion problems, and for access to our full range of stable, high-performance flexographic inks, please contact our technical service team. We are dedicated to providing the support and products you need for successful printing.