Solutions to Dot Gain, Color Deviation, and Poor Overprinting in Gravure Printing

In gravure printing production, dot gain, color deviation, and poor overprinting are common issues affecting print quality. Many operators directly blame the ink or equipment, ignoring the core impact of process parameters and material compatibility. Based on Shunfeng's years of industry experience, solving these problems requires comprehensive optimization of ink properties, printing conditions, and substrate selection. Below are the specific causes and solutions.

Printing Conditions

• Problem Manifestation: Abnormal increase in dot size after printing, color saturation deviating from standards, and color mixing, show-through, or insufficient adhesion during multi-color overprinting.

• Solutions: Optimize the matching of printing pressure and anilox roller line count, reduce printing speed to minimize dot deformation; adjust drying temperature and air speed to ensure complete drying of the previous ink layer before overprinting; use a spectrodensitometer to monitor color deviation in real time and adjust ink ratios promptly.

Ink

• Color Strength and Overprinting Performance of Ink: The color strength, transparency, and drying speed of ink directly affect dot gain and overprinting effects. Dot gain usually stems from low ink viscosity and high pigment concentration; poor overprinting is mostly related to poor interlayer adhesion and mismatched drying speeds. For example, water-based inks are prone to dot blooming in high-humidity environments, while solvent-based inks require controlled evaporation rates to avoid overprinting color mixing.

• Solutions: Select inks with stable color strength and moderate transparency, optimize the pigment dispersion process to reduce color concentration; add an appropriate amount of retarder to adjust drying speed, or use an overprinting promoter to enhance interlayer adhesion; for dot gain issues, improve by increasing ink viscosity or replacing with lower color concentration ink.

Substrate

• Surface Treatment and Ink Adhesion: The surface energy and roughness of the substrate determine the adhesion and spreading of the ink. Insufficient surface treatment can cause ink shrinkage and dot gain, while uneven substrate roughness can lead to overprinting show-through.

• Solutions:

◦ For plastic films (such as BOPP, PET), use corona treatment to increase surface energy and ensure ink adhesion.

◦ For paper substrates, select paper with high surface smoothness and perform pre-coating treatment to optimize ink spreading.

◦ For special substrates (such as aluminum foil), use a dedicated adhesion promoter to enhance the bonding force between ink and substrate.