Technical Tutorial: Pankaj Sharma, deputy manager business development at Siegwerk India talks about Emulsification

Wednesday, August 31, 2011

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.

Solution to the problem
• 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 optimise the adjustment of the inking and dampening rollers.

•   Where there is less ink taking, an additional ink stripe may be introduced to stabilise the balance of ink and water.


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