To test the dry properties of an ink as e.g. colour, density, light fastness, chemical resistance and so on, a print on a substrate is necessary. After drying the desired property can be measured. Most of these printability tests are performed on the base of a known ink film thickness on the printing form (printing disc); the real amount of ink on the paper is not known. In many cases it is better to know exactly the amount of ink on the paper because small differences can influence the properties too much. For that reason it is advised to make the print in combination with the ink transfer in g/m². Direct measurement on the printed paper is not possible. For that reason the ink transfer is calculated in g/m2 from the difference in weight of the printing form before and after printing and the sizes of the print. The test in this leaflet is described for an ink to be tested on a standard, very smooth paper as APCO II/II. The method can be used to test very smooth papers with a (standard) ink as well. The following listing shows the different methods, dependent to the roughness of the paper used:
W50 rubber 85 Shore A for very smooth papers
W72 rubber 65 Shore A for smooth/rough papers
W80 rubber blanket for very rough papers
W81 aluminium for letterpress
All these tests are described for conventional offset inks. For UVinks special printing forms, top roller for the inking unit and a UV dryer have to be used. Consult IGT Testing Systems for the right articles.
The paper strip is printed with an ink on the printability tester. Before and after printing the printing form (disc) is weighed on a precision scale with an accuracy of 0.1 mg or better. From these weights and the sizes of the print the ink transfer as g/m2 can be calculated. After drying the ink the printed samples can be used for further determination of dry properties as e.g. colour measurement, abrasion resistance, chemical resistance, light fastness and so on.
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 4 and ink pipette follow the instructions of the manuals, IGT information leaflet W100 and the displays accurately.
• Handle the samples carefully.