engleski

DETERMINING THE CORRELATION BETWEEN TOTAL HARDNESS OF WATER AND SPECTRO-DENSITOMETRIC CHARACTERISTIC OF PRINTING QUALITY

The wetting solution plays significant role in offset printing process, helping in separation of printing from non-printing areas of the printing form. The wetting solution is characterized by the share of isopropyl alcohol, pH value, electrical conductivity, temperature and water hardness, which is a direct consequence of the presence of various salts in water. It is proved that setting the optimal total hardness of water, which is recommended to be kept from 8od to 12od of German hardness, could extend the service life of metal components and machine parts in contact with the wetting solution, because of reduced corrosion and lime scale sedimentation. It also extends the life of the rubber rollers in contact with the wetting solution. However, there is an issue of particular owner’s and management’s interest: would they get prints of higher quality if they install system for regulation of the water hardness? In this paper an attempt was made to determine the correlation between the total hardness of water and some characteristics of print quality (tone value increase, range of reproduced tonal values, maximum screen ruling at which it is possible to get a clear image without defects). In the experimental part a single color sheet fed offset printing machine will be used, on which all printing conditions will be kept constant, except the hardness of water to be used in the wetting solution. Soft, medium hard and hard water will be used. Key words: wetting solution, water hardness, print quality

wetting solution, water hardness, print quality

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