Washing and cleaning solutions for use in offset
printing are mixtures of different, chemical compounds such as hydrocarbons, solvent naphthas, oils, tensides, corrosion inhibitors and others. The different compositions of the washing solutions are adjusted to the specific intended use.
For use in heatset printing further regulations are to be observed for the washing solution, as the inks are heated in the continuous-flow drier far above the flash point of their solvents. Up to 85% of the solvents will evaporate. Oxygen will get into the interior of the drier through the opening and will mix with the vapours. In order to avoid the risk of an explosion the air is sucked out.
The washing solution and the maximum throughput when washing the blanket have to be adapted to the exhaust volume of the ventilation of the drier.
Inking rollers or ink fountains are cleaned with undiluted washing solution as in this case only inks will have to be dissolved. In addition it is recommended to use roller cleaning paste especially in case of an ink change from dark to lighter color tones in order to achieve a fast and effective cleaning. The use of a cylinder cleaning paste is recommended for cleaning soiled metal surfaces.The paste will remove all residues and will protect the surface of the cylinder against resoling.
In the course of time components of paper and ink will deposit on the rollers which can cause considerable trouble in the printing process. Especially calcium carbonate will considerably influence the emulation behaviour and ink transport.
The regular cleaning and maintenance of the printing machine is one of the most important conditions for the trouble-free production course at the end of which a satisfying printing result is expected. The washing solution will etch printing ink components. Washing solutions mixed with water will remove the water-soluble accumulated dirt (such as paper components) together with the printing ink. Automatic washing units (s. illustration) such as brush or blanket washing units are meanwhile standard equipment for the cleaning of blankets. A considerable amount of time, expenditure and washing solutions is the result when they are used.
