Examination of dot losses in ozasol plates during offset printing

The offset printing system is a widely used printing method in the printing industry. In offset printing, during the transfusion of image to print material it is highly important that in terms of quality, dots are transferred in the correct manner. However, in the transfusion of dot to print material problems especially arise in high circulation jobs.In this study; the sample prints were carried out to determine dot losses in ozasol plates during offset printing by using various parameters. To establish the effect of the pH value of the fountain solution on dot losses, the pH value was changed every 3 hours (1.5, 3.0, 4.5, 5.5 pH values) during a total of 12 hours of printing. The effect of the pH value of the fountain solution on dot losses was investigated by measuring dot values of 20%, 50%, 70% and 90% of the printing samples taken at specific time periods (10. 20. 30. 40. 50. 60. 90. 120. 150. 180. Mins.), for every pH value. To determine the impact of the pressure on dot losses, starting from the ideal pressure value for the print material used (150 g/m² glossy paper), the pressure value was increased by a unit value of 0,75 at every 10 000 print and 8 hours of printing was carried out for the increased pressure. At the end of the tests it was determined that fountain solutions with acidic properties had an early effect on the plate and that after a short while it was the cause for dot losses. Furthermore, in prints carried out with increased pressure that it was observed middle sized dot values weakened after a while during printing. By examining the factors effecting dot losses, using the results of the tests and research carried out solutions are suggested and presented to the printing science.Key Words : Offset printing, osasol plate, dot loss