PRESS
Emancipation from emulsification

December 2008

multipage

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. Emulsified printing inks lengthen drying times and increase the risk of deposits. Take the following corrective steps:

• Set the ink and dampening balance correctly, and check it continuously throughout the run

• If the ink emulsifies, wash the rollers and re-establish the smearing limit

• Check the dampening solution and change it regularly (the ideal alcohol-based 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 or 50°F to 59°F; for solution using an alcohol substitute, pH should be 3.8 to 4.6, and the temperature should be 12ºC to 17ºC or 54ºF to 62ºF)

• On an Alcolor dampening unit, separate the intermediate roller from the inking unit and install cross-flow ventilators

• Avoid frequent phases of pre- and post-dampening during makeready or stoppages

• Inspect and optimize the adjustment of the inking and dampening rollers

• Where less ink is being taken, add an ink stripe to stabilize the ink-water balance