Anthony Seric, technical manager at DS Chemport (Australia) explains the reasons pressroom chemicals are necessary, what they should include, and what progress is being made to green chemicals.
Press chemistry refers to a range of products that enable printers to ensure that printed work produced from a press is of satisfactory commercial quality. In lithographic printing, press chemistry includes solvent washes, silicone emulsions, plate cleaners, maintenance products, but first and foremost, fountain solutions.A fountain solution is a water-based product with the primary functions of wetting the non-image area of the printing plate and de-sensitising it to printing ink. A good fountain solution is also expected to:
• to render the non-image area of the plate water receptive (hydrophilic),
• to clean and to renew the anodised surface of the non-image area,
• to remove and wash away grease, oil, pigment, emulsified ink and inorganic salts and to prevent oxidisation of the aluminium surface
• cool the surface of the plate
• give effective and efficient plate wetting
• minimise pile and give long runs between wash ups
• give good ink trapping and produce a sharp print, and
• have a wide tolerance to water and ink settings.
Contrary to some beliefs, ink and water do mix readily and it is when they do not mix correctly that printing problems occur.
The expected performance of a good fountain solution is the same on all presses and on all dampening systems, however, this performance can only be achieved by understanding the conditions under which the press operates, ie type of press, type of ink and paper used, blanket condition, press speed, the dampening system of the press, water quality, temperature at which the press operates, strength and viscosity of the inks used. For example, the operating conditions of a web press are different from a sheetfed press and this must be taken into consideration when formulating a fountain solution.
So how do we turn water into a fountain solution?
IN early lithographic printing, all that was needed was a bit of gum and a dash of acid to make a pretty good fountain solution. Of course, presses were originally much slower, run lengths were much shorter and the print quality in many cases would not even come up to today's waste standard. To meet the current expectations of modern, fast and high quality printing, what is needed is modern, sophisticated, high quality chemistry. To do that, present day fountain solutions contain many individual components, with each component included at the right level and balanced with the other components in order to provide the desired effect on the press. The number one component of the fountain solution is water – it must be clean and of good quality. Other components commonly found in fountain solutions include:
• Gums, such as gum Arabic, which are used to produce a highly water receptive surface on the non-image area of the plate. The gums are also known as desensitisers, because they desensitise the non-image area of the plate to printing ink.
• Acids and Alkalis, including phosphoric acid and caustic soda, are included at a low concentration to give the solution a particular pH. They mildly etch the surface of the plate, continuously regenerating it, keeping it clean and water receptive.
• Surfactants, or wetting agents, are also commonly known as detergents. These are used to make the solution wetter. They do this by lowering the surface tension of the fountain solution so that it spreads more rapidly and effectively on the surface of the printing plate.
• Solvents are also utilised in the manufacture of fountain solutions and include glycols, alcohols and glycol ethers. They assist the plate wetting, enhance the ink-water balance and modify the viscosity of the solution.
• Ancillary components include pre-servatives, antifoams and colourants.
The environment
Through the 20th century, with the advent of heatset and faster sheetfed printing, printers turned to the addition of isopropyl alcohol to overcome limitations in the dampening system. This became a standard practice for many years, however, during the 80s and 90s with growing awareness of the effects of evaporated solvent on operators and the environment, insurance risk and increasing government regulation, alternative solutions needed to be found. An entirely new breed of alcohol-free fountain solutions was created, but more importantly, a drive to produce more friendly press chemistry products began.
Today and into the future, product development focuses on generating low VOC, non-flammable, zero-aromatic, non-hydrocarbon, heavy metal free products via the use of raw materials that are produced from environmentally sustainable resources.
Unfortunately, in recent times we have been inundated and overwhelmed by these phrases and catchcries in the wave of green information that we are exposed to on a daily basis.
In truth, the move to products of this type is a slow, but steady one. Whether driven by regulation or environmental conscience, the printing industry is certainly moving in the eco-friendly direction. DS Chemport places a strong emphasis on developing new products utilising raw materials of this type.
These government mandates and rules are seen by some as yoke that must be borne, but within DS Chemport and the global network of Fujifilm companies, they are seen as a challenge that we strive to meet and overcome.
