Studies on the depth of ink penetration in offset paper

Ink penetration is an important stage in printing process and has a great impact on ink film forming and ink drying. The ink penetration depth into offset paper was studied in this work. According to the differences of certain physical properties, five offset paper were selected. Their properties including thickness, tightness, smoothness and K&N absorbency value were measured. The five offset papers were printed on an IGT printability tester using the same ink and under nine different printing conditions. Then the total ink penetration depth, the ink penetration depth under pressure (during printing) and the ink penetration depth under no pressure (after printing) were measured respectively. The results showed that both the tightness and smoothness of offset paper had impact on ink penetration into the paper surface layer and its internal pore structures. The ink penetration depth increased with increased printing pressure and decreased printing speed; In addition, the total ink penetration depth was about 1/3 similar to 1/4 of the thickness of given offset paper; The ink penetration depth under pressure and under no pressure were 80% and 20% of the total ink penetration depth; So the ink penetration depth under pressure dominated the ink penetration process during printing.