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Offset printing is the most popular process in the present printing industry. It amounts to over 60% of the total commercial printing production in the world. One of the needs for the printing presses in the printing field is the production of high and stable quality printing with few operators and less skills. The key factor is how inking should be controlled in the offset printing. For that purpose many devises and systems have been developed and applied to printing presses, for instances, control of ink temperature, ink supply control with close loop circuit, simple inking device such as keyless inking system, and so on. Almost all of them seem to be neither successful in practical use, nor accepted in the market. The reason is clear that they all disregard the important function of dampening solution in the offset printing process. According to Mitsubishi's researches, dampening solution has two functions; 1) Protection of the non-image area from inking 2) Optimization of tone reproduction The second item is corresponding to the "balance" of ink and dampening solution, but the true meaning of the balance has never been analysed. Mitsubishi's basic researches of the inking behavior on printing presses have made it clear that the good balance is equivalent to a optimum emulsion state of ink and dampening solution on inking rollers. The optimum state is explained with printing results.
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