Most commonly picking of paper is defined as the damage of the paper surface during the printing operation. At the time the printing form is lifted off the paper the ink is exerting a certain force on the paper. This force is increasing with an increase in the viscosity and tack of the ink and the printing speed. When this force exceeds a certain value, the surface of the paper will be damaged. This damaging is tested as pick velocity and/or pick resistance in W31, W38, W65 and W75. Sometimes this qualitative pick testing method does not show differences between papers with a poor pick velocity or pick resistance, e.g. newsprint. For these types of papers it can be advised to use a quantitative testing method to test the surface strength. This test is called “linting”.
A print is made with a test ink on the paper with an IGT printability tester. An increasing speed is used. The picking result is observed visually as the amount of fibres which has been pulled off from the surface of the paper.
Method of operation
• It is recommended to execute the test in the standard atmosphere; to most standards it is 23.0 ± 1.0 °C (73.4 ± 1.8 °F) and 50 ± 2% rh.
• For the operation of the AIC2-5T2000, Global Standard Tester, High Speed Inking Unit and ink pipette follow the instructions of the manuals, IGT information leaflet W100 and the displays accurately.
• Handle the samples carefully.