Test set for Wet-on-wet printing tests in combination with an IGT printability tester.
When inks are used on multi colour offset printing presses the second ink film is printed over the first ink film while it is still completely wet. In order to do this the inks must be adjusted in tack and/or viscosity. The systems to measure tack and/or viscosity measure without taking account of absorption by the paper. On the printing press, the low viscosity ink components will penetrate into the paper and the tack and viscosity of the ink will increase rapidly, as soon as the ink is transferred to the paper. The longer the ink is on the paper, the larger the increase of tack and viscosity will be. The time interval between individual prints differs considerably in various types of printing presses. On the press these interval times are between 0.03 s and 3 s. If the colour sequence is not good this can show "Ink trap mottle".
For proper adjustment of ink for wet-on-wet printing a printability tester, operating with selectable time intervals is essential.
Can be used in combination with the following IGT Printability testers:
For more information look at the test method information W46 Wet-on-wet printing (rubber 85 shore) & W69 Wet-on-wet printing (rubber 65 shore)