Tips & Tricks: Emulsification

Emulsion is a mixture of ink and dampening solution. In this process, dampening solution is distributed evenly throughout the ink in small droplets. The proportion of water in a "stable emulsion" is around 20%. If higher, then an ink's splitting properties are reduced, and fluid viscosity is interrupted. As a result, the emulsion becomes unstable, the ink "builds up", and it "emulsifies". Too large a proportion of dampening solution in the printing ink, or too low a pH-value fosters emulsification. Printing inks react differently, depending on what type they are: blended inks, dayglo, or metallic inks are more sensitive than inks in the normal scale. Emulsified printing inks will increase drying times, as well as increasing the risk of deposits.  

Remedy:

• Set the ink and dampening balance correctly, and check on it continuously throughout the print run
• In case of emulsified ink, wash the rollers, and re-establish the smearing limit
• Check the dampening solution, and change it regularly (the ideal dampening solution has a water hardness from 8 to 12°dH, a pH-value from 4.8 to 5.5, and a temperature from 10°C to 15°C (50°F to 59°F)
• On an Alcolor dampening unit: separate the intermediate roller from the inking unit; install cross-flow ventilators
• Avoid frequent phases of pre and post-dampening (during make-ready or stoppages)
• Inspect and optimize the adjustment of the inking and dampening rollers
• Where there is less ink taking, an additional ink stripe may be introduced to stabilize the balance of ink and water