In order to evaluate whether an ink complies with this part of ISO 2846, it is necessary to print a number of
samples, each of known ink film thickness, which adequately r epresent the range of ink film thicknesses
specified i n 5.3. These samples may be prepared on a printability tester by r unning up a small quantity of ink
on the inking system, weig hin g the printing forme prior to printing a nd then pri nting the test sample on the
reference substr ate. The printing forme is then re-weighed and the difference recorded. If the mass density of
the ink is known (which may be determined by weighing a known volume of ink) and the printed are a is
measured, it is possible to calculate th e ink film thickness applied to the paper from the difference in mass
before and after printing. The ink film thickness, s, may be calculated using the following equation: