Switching to alcohol free printing

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Switching to alcohol free printing
Text writed in collaboration with Prisco®.

There is no such thing as a “universal” fount solution and often several additives have to be tested before attaining the best result. Numerous products are available and various developments continue to facilitate their use.
To facilitate the switch over to alcohol free printing, several key parameters have to be taken into account:

The surface tension: Each press and fount solution system require a specific surface tension for an optimal result. With the present generation of fount solution additives developed by manufacturers such as Prisco®, it is possible to adjust the surface tension as desired without any problem.

The viscosity: Unlike alcohol itself, alcohol substitutes do not increase the viscosity of the fount solution. When the isopropanol is eliminated, the fount solution becomes more fluid and, if the press is not correctly adjusted, the fount solution system does not convey sufficient solution to the plate. The water / ink balance goes out of sync and leads to scumming of the plate.

The hardness of the rollers: The hardness of the rollers and how they are adjusted are both very important. It is recommended to use metering rollers with a Shore A hardness of 18 to 25 and dampener form rollers with a Shore A hardness of 25 to 28. A more moderate adjustment of the pressures on the dampening rollers and the contact between the dampening rollers and the printing plate is also recommended. A common error consists in increasing the speed of the metering roller whereas in fact it needs to be reduced.

Ink-water balance: At the heart of the emulsion, the alcohol acts as a diluent for the ink. By eliminating the alcohol, less water is required. Various industrial studies and trials have shown that the degree of wetting may be reduced after eliminating the isopropanol. Since less adjustment of the water and ink is required, it is easier for the printer to maintain the water / ink balance. A thinner and very concentrated ink film
leads to sharper dots and makes colours more intense. Drying is more rapid, since there is less liquid in the ink film. 
Before switching over to alcohol free printing, certain basic recommendations should be followed:
Involve both management and print shop personnel. Consult a specialist company.
Clean and deglaze the inking rollers of the press.
 Clean the fount solution circuit. Empty and rinse out the fount tanks. Adjust the temperature to 15°C ± 10 %.
 Use an additive / metering system adapted to the equipment, the fount solution system and the tap water used.
 If necessary, replace the rollers with rollers of more suitable hardness. Reduce the contact pressure in the fount solution system.
 Use new inks for starting up the press. Initially adjust the settings at a high and uniform level.

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