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Q & A / Advice - The Alcohol Debate:
The alcohol free debate continues, with printers and suppliers being divided
over the effectiveness of alcohol free or reduced alcohol printing.
Although there is a growing number of pressrooms where presses are being run
successfully without alcohol, the rate of increase has been relatively slow, given
the benefits that can be realised.
Running alcohol free can be extremely effective, with improvements in quality
and reductions in production costs. Before discussing these benefits in greater
detail, however, it is important to understand the role that alcohol has
traditionally played in dampening systems and the inherent problems it can
bring.
What is the function of alcohol?
The fountain (dampening) solution plays a critical role in the printing
process, being used to establish the correct ink/water balance, during
both the start-up and the printing operation. For this to occur it is helpful
to reduce the surface tension of the solution, to the point where it flows
evenly through the dampening roller system, giving a uniform film of
moisture on the plates and producing a fine water-in-oil emulsion with the
printing ink.
Water has a high surface tension. Water droplets on the surface of a
printing plate are almost spherical, with a small contact area. Reducing
the surface tension, by adding alcohol or Vegra Alcodamp, increases the
contact area, providing greater coverage of the plate from a smaller
volume of water.
The ink/water balance, enhanced by the use of alcohol, is obviously
important if the fountain solution is subsequently to be removed from the
non-image areas by the ink rollers, without affecting the properties of the
ink itself. The use of alcohol, with a high rate of evaporation, also helps to
reduce the water content of the fountain solution, once it has served its
desired purpose; this evaporation also has a cooling effect on the ink,
In addition, the even application of fountain solution is a particularly
important factor in today’s high speed presses, where continuous
dampening systems with chrome plated rollers are used. The low
hydrophilic properties of the chrome and the high surface tension of
water, make it difficult to form a consistent film across the entire width of
the roller. The addition of alcohol reduced the surface tension, to allow an
even film of water to be created.
Tests have shown that the ideal ink/water balance is achieved when the
thickness of the fount solution on the plate is half that of the ink - typically
one micron of fount solution to two or three of ink.
What problems does the use of isopropyl alcohol present?
Although the use of alcohol in dampening solutions can help to enhance
the printing process, it can also create a number of problems:
o
Isopropyl alcohol has a hardening affect on rollers. This requires
roller pressures to be frequently monitored and adjusted. Alcohol
can increase the hardness of rollers by as much as 75-100%
within the space of three months.
o
It is often difficult to maintain a consistent concentration of alcohol
in fountain solutions. As a result, the viscosity of the solution can
change, affecting both press performance and print quality. A little
known fact is that raising the concentration of alcohol actually
increases, rather than reduces, the viscosity of the fountain
solution.
o
Isopropyl alcohol has a strong and generally unpleasant odour. In
its undiluted form it has a very low flash point; even a
concentration of only 20% alcohol in water has a flash point of
30°C.
o
Alcohol has a VOC (volatile organic compound) content of 100%.
o
New regulations mean that isopropyl alcohol now presents a
number of transportation and storage difficulties. It is becoming
increasingly difficult to transport by road, with transportation costs
set to rise still further. Ultimately, only specialised carriers will be
able legally to move ‘highly flammable’ materials; already, only a
few carriers will handle alcohol - and then at a premium.
o
Insurance companies charge higher premiums because of the fire
risk involved with storing and using isopropyl alcohol.
Your choice:
Alcohol replacements are now widely available. Many of these, however,
can be unsuitable for different types of presses, or combinations of press,
ink, paper and so on.
Common problems include:
o
Foaming.
o
Ink drying.
o
Difficulty in controlling ink/water balance.
When choosing a fountain solution, it is therefore important to work
closely with a manufacturer that can offer a wide range of alcohol-free
products.
The leading European manufacturer of specialised dampening additives
is the Germany company, Vegra GmbH, for which Pomeroy is the sole
UK partner. Vegra is recognised throughout the printing industry for the
quality and performance of its products and has considerable experience
in the development and use of fountain solutions.
Vegra’s most recent range of products includes the Alcodamp series of
alcohol replacement fountain solutions, which provide the following
advantages over traditional alcohol based systems:
o
Alcodamp has no degenerative effect on press components, such
as rollers and blankets.
o
Alcodamp is highly stable and is not subject to special
transportation or storage regulations.
o
Alcodamp is very low in harmful VOCs. It is odourless and non-
hazardous in the working environment.
o
Alcodamp contains no harmful ingredients and is biodegradable.
Vegra Alcodamp provides:
o
Perfect interfacial tension between inks and the dampening
solution.
o
Enhanced ink/water emulsion, resulting in cleaner, brighter
colours.
o
A more consistent print quality, as variations caused by fluctuations
in alcohol content are eliminated.
o
Lower dot gain/open screens.
o
Simple changeover. Only basic preparation is required, with the
existing fountain concentrate and alcohol literally being replaced
by Alcodamp.
o
Simplified preparation and control of the dampening solution, with
the elimination of alcohol dosing equipment.
o
Quick starting and rapid plate cleaning.
When selecting an alcohol-free or reduced alcohol fountain solution, it is
important to know the quality of your dampening water. In particular, the
hardness and hydrogen carbonate content should be checked, if the best
performance is to be achieved.
Further products to aid in the reduction of IPA in the pressroom, are
detailed in the ‘IPA Reduction’ section of this website.
© Pomeroy Pressroom Products Ltd 2010
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