Even when using the same dilution, why does the same ink not have the same covering?
The viscosity of the ink strongly depends on the temperature at which it’s printed: in warmer seasons it is more fluid than in colder seasons and so the addition of the same quantity of diluents in both cases may cause different viscosities of the ink. Since the inking is directly proportional to the viscosity (in printing systems with rubber roller mainly) a different charge of ink with the same dilution, may occur. Even printing with constant viscosity is a good working method, although it’s not always decisive: during winter a high dilution (with resultant high reduction in pigmentation)...
Read MoreWhat is the cause of cratering?
Cratering defects also called fish eyes, are generally caused by the antifoam agent present in the ink or by the presence of non-compatible substances. Disproportionate addition of antifoam or its low compatibility may generate this kind of defect and the effect is more visible on low or not absorbent supports, such as glossy paper or plastics. Therefore, it is appropriate to use an antifoam which is suitable for the kind of support to be printed on, and to be used in the right proportion. In order to solve this problem, it is necessary to add products able to increase the wetting of the...
Read MoreIn terms of long-term production, the ink sometimes tends to produce foam. How can the problem be prevented?
Foam can be defined as gas which has been stabilized in a liquid medium. The formation of foam primarily occurs in water-based inks that contain surfactants (used to improve wetting of the support, the dispersion of pigments and the emulsification of resins), especially with pumping systems (that blow air into the ink) and during long-time production. The addition of low quantities of antifoaming agents (better if predispersed in water in a ratio 1:1 and directly sprayed on the foam) causes the destruction of the foam layer and reduces the problem. Sometimes it is very difficult to demolish...
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