Introduction:
Many times paper is printed on both sides. The ink penetrates into the paper from the one side to the other side. When the ink penetration int o the paper is very strong the ink can be visible at the other side and reading the printed matter at the other side can be disturbed. In this case we speak about striking through. This phenomenon can be tested with the print through or striking through test. The method in this information leaflet describes the method with rubber of 65 Shore A, leaflet W43 describes the method with rubber of 85 Shore A
Principle:
Paper is printed at one side. The ink penetrates into the paper. After a certain time the ink does not penetrate any more. The
whiteness at the back of the print and at the paper without the ink is measured. The print through is calculated as a percentage of the original whiteness of the paper.
Assessment
1. Measure the whiteness on the back of the paper strip on the place where the paper has been printed (Rb) and on the place
where the paper has not been printed (Rw).
2. Calculate the print through as:
Print through = (Rb : Rw ) x 100%
3. Repeat the points 1 and 2 for every strip.
4. Calculate the average and if desired, the standard deviation. Sometimes it can be useful to mention the highest and
lowest values as well.