The concept of ink balance

Offset is the use of oil and water immiscible with each other for ink transfer. Theoretically, only when there is a strict boundary between the water film on the surface of the blank part of the printing plate and the ink film on the surface of the graphic part of the printing plate, the ink and ink will not wet each other, ie the ink and water balance will be achieved. However, the printing plate, the watering roller, and the ink roller transfer water and ink during high rolling and mutual rolling. The above ideal static balance is difficult to achieve in the dynamic printing process.

The mixing curves of the three different inks, the ordinate is the amount of water mixed in the 100g ink measured after mixing the wetting liquid and the ink, and the abscissa is the mixing time of water and ink.

Curve A indicates the ink that is most likely to be mixed with water. Since the water content in the ink is too high, the ink head is too short, and the ink is difficult to output from the ink fountain of the printing press, so it is not suitable for offset printing; the curve C indicates that the ink is not easily mixed. Water ink, the ink is almost repellent to the water, the fountain solution squeezed into the ink in the printing quickly separates from the ink, attaches to the surface of the ink and forms a water film, which hinders the ink Transfer to the blanket.

Experience has shown that this ink has poor transfer performance and may cause prints to be printed and not used for lithographic printing; only the ink of curve B can make the printing run smoothly. Experiments have shown that when the ink of curve B has a water content of 26 % (ie, when 100g of ink contains 26g of water), the print quality is best.