In offset lithography, the dampening rollers transfer the press ready, diluted fountain solution to the printing plate as a way to render the non-image areas of the plate ink-repellent. Isopropyl alcohol, (Isopropanol or IPA) has been, and in some parts of the world still is used, as a popular dampening solution additive because of the advantages it offers to the lithographic process.
The advantages offered by IPA can be summarised as follows :-
– Surface Tension Reduction
IPA reduces the surface tension of the fountain solution (making it wetter), so it can spread quickly and more uniformly over the surface of the printing plate.
– Viscosity Increase of the Fountain Solution
This allows a thicker film (more water) to be delivered to the plate via the dampening roller train, resulting in faster printing.
– IPA Readily Evaporates
So less water is delivered to the paper. Also, as the IPA evaporates, it removes heat from the rollers and the ink.
– Alcohol Dampening is More Forgiving
to some extent, it masks problems that can occur with an old press, a press that is not properly maintained, lack of operator skill, or inaccurate press settings.
These are great advantages, so we must ask why a printer would want to print alcohol-free. The answer is that IPA is flammable, toxic, volatile and expensive.
Generally up to 5 times more IPA is added to the dampening solution than fountain solution (3% fountain solution with up to 15 % IPA). So, apart from the cost factor, eliminating IPA from the printing process comes from environmental, health, and safety concerns and regulations.
Alcohol-free printing, when done properly also offers great advantages, which include lower cost of printing, lower ink/ water settings, higher density print, due to the fact that the ink is not diluted with alcohol, resulting in sharper dot and lower tendency for the ink emulsification.
Beginnings of IPA
In the early days of trying to print without IPA, fountain solution suppliers formulated products identified as “alcohol substitutes”. Such products contained various solvents, which were expected to mimic the performance of IPA. These early products offered only a limited degree of success and they often failed due to a very narrow window of tolerance on the press.
Today, more advanced formulations can be more accurately called “alcohol-free.”
We must understand that alcohol-free fountain solutions do differ significantly from fountain solutions formulated for alcohol dampening. Alcohol substitutes differ from IPA in several key properties, including viscosity, surface tension, pH and conductivity. We must also remember that alcohol-free fountain solutions are not universally suitable for every press, every dampening system and for every printing job. Therefore it is very important, that the printer communicates closely with their fountain solution supplier, so that they are supplied the right product for the press and its dampening system.
Successful alcohol-free printing requires a close cooperation, a partnership between the printer and the fountain solution supplier.
The most common reason that alcohol free printing fails is the lack of such close cooperation – partnership between the printer and the fountain solution supplier.
The supplier is often too shy to point out to the printer that the press settings may be wrong; the rollers are too worn or too hard, that the water used to dilute the fountain solution is unsuitable due to its excessive hardness and high mineral (salt) content.
The fountain solution supplier is reluctant to point out these problems to his customer, because he is does not want to tell the printer how to do his job. So when the fountain solution fails, he will try to modify it, to compensate for the press short comings, even though he knows that the product is working well at many other accounts. Such action will not only compound the problem, but will most importantly erode the confidence of the printer in the supplier and his product.
Successful Alcohol-Free Printing
Assuming, that the fountain solution is well formulated, suitable, tried and tested for the press and the dampening system it will be used for, there is absolutely no reason, why it should not be successful. But to make it a success, the printer must also do his part, ensuring proper press and roller settings, correct roller hardness and roller tolerances, making sure that the rollers are deglazed and any calcium build up is removed.
Importantly, the printer must also make sure that the water quality is suitable for lithographic printing. A good, professional fountain solution supplier will be able to assist with all necessary tests and measurements to ensure that all these requirements are met.
The outcome will be a successful alcohol-free printing, better print quality, lower cost of printing, less waste and a safer, more environmentally friendly pressroom.