Water Process

The composition of water is determined by the geological strata in the catchments-area and by any subsequent treatment. The following parameters are of importance for offset printing:

Total hardness

Total hardness indicates the amount of calcium and magnesium salts dissolved in the water. In Germany, total hardness is defined as German degrees (°d) hardness. Optimum hardness for offset printing ranges from 8 °d to 12 °d. When using water with a high total hardness, as well predominantly mat-coated stock, ink rollers may tend to strip (especially in the red unit).

Stripping is caused by deposition of poorly soluble calcium compounds in the pores of the rubber rollers, which then clog up, becoming increasingly hydrophilic, and greatly disrupt ink transport in the inking unit. Two methods are possible to eliminate these problems:

The tap water that is used can be softened or de-ionized.
A recommendation of the optimally adapted damping solution additive.
Attention: For use in offset printing, it is necessary to readjust de-ionized or softened water again, by means of a re-hardening agent (SALINOFIX 5005 09), to approx. 8 – 12 °d.
Special damping solution additives, formulated to prevent the formation of poorly soluble calcium salts, can be used.

In any case, already existing deposits on rollers need be removed by means of special cleaning agents such as Roller cleaning jelly 10 T 0023.

Hydrogen carbonate concentration

All waters from natural sources contain hydrogen carbonates which show a slightly alkaline reaction and, therefore, cause a rise of pH of the damping solution. The pH of water containing large amounts of hydrogen carbonates may even lie above the range considered to be favorable for printing. For this reason, we adjust the buffer in our damping solution additives to the hydrogen carbonate content of the water.

Chloride, nitrate, sulphate

Corrosion of certain metals may be caused or increased by water components such as chloride, nitrate, and sulphate. Therefore, machine manufacturers specify limits for the content of such products in the water. When these limits are exceeded, it may become necessary to install a water conditioning (reverse osmosis) filtering system.

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