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 “stabile emulsion” is around 20 %. If higher, then the ink’s splitting properties are reduced, and the ink flow
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.
- Set the ink and dampening balance correctly, and check on it continuously throughout the printing process.
- 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.