Ink Film Thickness
The thickness of the ink film on the rollers is a very important consideration in printing. Typical ink film thickness on the lithographic press is 0.2-0.4mils, depending on the ink color and printing sequence. The press operator should control the amount of ink being carried by the inking system for more precise control of ink density and color and to avoid problems related to excessively thick or thin ink films.
Common problems resulting from an excessively thin film of ink are low color strength and color saturation, low gloss, incomplete coverage of paper, picking, and hickeys. Also ink or water balance is difficult to achieve.
Common problems resulting from an excessively thick film of ink are increased ink consumption, ink set off, drying problems, slight degradation of light colors, graininess of print due to irregular dot gain, excessive emulsification of ink, and low contrast in the shadows due to dot gain.
During the pressrun, the press operator should adjust inking levels until the maximum print contrast level is obtained, because the higher the print contrast, the greater the number of tones that can be distinguished between the 75% tint level and solid ink the density. As the press operator increases ink density by increasing ink feed, the print contrast will increase until a point is reached where further increases in density will causes lower print contrast values.
Edit by Vikas
15 April, 2012
