Studies on wet picking and wet resistance of offset paper

Surface wet picking and wet resistance can occur in offset printing process because offset ink is of high tack and viscosity, the printing speed is relatively high and the dampening solution (water) is used in offset printing process. In this paper, the impact of wet picking and wet resistance on two types of paper, coated paper and offset paper were studied using IGT printability tester to simulate the real printing process. The results showed surface wet picking and wet resistance occurred on both coated paper and offset printing paper. In addition, the degree of surface wet picking and wet resistance in grain direction (machine direction) and at the wire side of the paper was lower than that in cross direction and the felt side of offset printing paper if the printing speed and the quantity of fountain solution were definite. But surface wet picking and wet resistance of coated paper were almost not subject to its grain direction and two-sides. The change patterns of wet picking and wet resistance were determined by the structure and performances of the paper samples.