Causes and Solutions for Ink Splashing in Printing
Release Time : 2025-01-16
Ink splashing, also known as misting, primarily occurs due to charged free ink droplets and similarly charged paper surfaces, which can adversely affect print quality. The occurrence of ink splashing not only pollutes the environment but also poses health risks to operators. Below is a brief analysis of this issue.
1.Causes of Ink Splashing
During the ink transfer process, when fibers on two contacting ink rollers are cut or elongated at two or more points, fragments are formed and take on a spherical shape due to surface tension. At this point, the double electric layer at the interface between the fiber and the fragment is disrupted, causing some charges to remain in the ink while others escape into the atmosphere with opposite charges.
As the fibers shorten, residual charges in the ink gradually accumulate on the ink rollers and paper surfaces. Since the fragments carry the same charge as the ink, they are repelled into the air when close to the ink rollers or paper, leading to splashing.
Using high-viscosity and low-quality binding agents in high-speed printing machines can cause the ink to stretch into long strands, resulting in significant ink splashing. Therefore, different models of printing machines require corresponding ink types for proper matching.
2.Factors Influencing Ink Splashing
(1)Ink Viscosity
If the ink viscosity is too high, it can easily stretch at the ink roller outlet and cause splashing, while also resulting in uneven ink transfer, fuzziness, and difficulty in peeling paper from the blanket, potentially leading to misalignment or ink loss. Conversely, if the viscosity is too low, the ink layer may not split well, leading to splashing, ink emulsification, floating debris, smudging, and enlarged dot patterns, all of which affect print quality.
(2)Ink Layer Thickness
Thicker ink layers on the rollers result in more significant ink splashing. For example, when printing on coated paper, an ink layer thickness of 1.2μm requires the ink to reach 2.8g/㎡; however, for offset paper, the ink must achieve at least 4g/㎡. When the paper's performance adversely affects ink adhesion, it can cause the ink roller to accumulate ink, leading to splashing.
(3)Smoothness of the Ink Roller Surface
If the surface of the ink roller is uneven or has dried cracks, some ink layers may thicken, increasing the amount of mist and making splashing more likely.
(4)Printing Speed
Increased printing speed can exacerbate ink splashing.
(5)Air Humidity
Low relative humidity promotes ink splashing, while increased humidity reduces charge levels and consequently the amount of splashing.
(6)Amount of Fountain Solution
Excessive fountain solution in the ink can lead to severe W/O type emulsification, dramatically reducing viscosity and shortening ink strands, resulting in significant splashing. Additionally, fountain solution that contaminates the ink may corrode metal rollers, creating a hydrophilic layer that repels the ink, leading to ink loss.
(7)Ink Binding Agents
High molecular weight ink binding agents can stretch into long strands during ink splitting, causing splashing.
3.How to Eliminate Ink Splashing
(1)Select Quality Materials
Use high-quality alcohol-resistant inks to accommodate high-speed printing.
(2)Regular Cleaning
Periodically disassemble and thoroughly clean the rollers to ensure uniform ink layers and improve transfer performance.
(3)Control Alcohol Concentration
Maintain alcohol concentration between 10% and 15%; both too low and too high concentrations are unsuitable.
(4)Moderate Use of Fountain Solution
The amount of fountain solution should not be excessive, as it can shorten ink strands and hinder printing.
(5)Utilize Electrolytes Effectively
Adding electrolytes to the ink can reduce splashing. As the conductivity increases with the addition of electrolytes, the ink splashing phenomenon may completely disappear.