Practical Guide For Offset Printing Ink: Causes And Solutions To Issues Such As Ink Misting, Plate Blinding And Strike-Through

• Cause Analysis

Offset printing ink issues: Abnormal viscosity is the core cause. Excessively high viscosity leads to splattering under strong force, while excessively low viscosity results in strong fluidity and easy flinging by rubber rollers. Poor antistatic properties of the ink cause charged particles to repel each other, triggering splattering. Uneven pigment dispersion and large particle impurities lead to splattering during printing.

Equipment factors: Improper rubber roller pressure-excessive pressure squeezes the ink to splatter, while insufficient pressure causes uneven ink transfer and excessive local stress. Worn, scratched or impurity-contaminated rubber roller surfaces disrupt uniform ink coating. Excessive printing machine speed results in shear force beyond the ink's tolerance.

Process and environment:Unsuitable workshop temperature and humidity-high temperature reduces ink viscosity and low temperature increases it, both triggering misting. Poor compatibility between printing speed and ink: low-viscosity ink paired with high speed or high-viscosity ink with low speed disrupts ink stability.

• Practical Solutions

Adjust offset printing ink: Add 0.5%–1% special anti-misting agent according to the machine model and paper type (excessive amount affects drying). Calibrate viscosity to 20–30 seconds (at 25°C, DIN4 standard) with a viscometer-add a small amount of ink reducer for high viscosity and thickener for low viscosity. Filter the ink through a 120–150 mesh filter screen to remove large particle impurities.

Debug equipment: Calibrate rubber roller pressure with a pressure gauge-0.15–0.25 MPa between ink distributing roller and plate cylinder, 0.2–0.3 MPa between blanket cylinder and plate cylinder, ensuring uniform pressure. Polish and repair worn/scratched rubber rollers, or replace severely damaged ones. Adjust speed based on ink viscosity: reduce speed for high-viscosity ink and increase speed for low-viscosity ink.

Optimize environment: Maintain workshop temperature at 20–25°C and humidity at 50%–60% to avoid drastic fluctuations. Install protective baffles around the printing machine to reduce misting pollution and facilitate cleaning.

• Case Reference

A food packaging factory had a 12% reject rate due to ink misting during carton printing. Troubleshooting revealed the ink viscosity was excessively high at 35 seconds and rubber roller pressure was over 0.35 MPa. After adjustments-adding 0.8% anti-misting agent, adjusting viscosity to 25 seconds, calibrating pressure to 0.2 MPa, and setting humidity to 55%-ink misting was completely eliminated, the reject rate dropped below 3%, and production efficiency increased by 15%.

(2) Plate Blinding: Causes and Countermeasures for Offset Printing Ink Adhesion

• Cause Analysis

Offset printing ink issues: Slow drying speed, excessive viscosity, large particle size or impurities lead to ink accumulation on plates and blankets, clogging dots.

Plate and paper problems: Worn or deformed plate dots cause uneven ink transfer. Paper dusting and linting mix impurities with ink and clog dots. Poor ink absorption of paper leads to ink retention on the plate surface.

Process parameters: Excessive ink coating, overhigh printing pressure, or faulty drying equipment (insufficient temperature, inadequate wind speed) cause ink accumulation, overflow and delayed drying.

• Practical Solutions

Optimize offset printing ink: Select fast-drying offset printing ink. Add an appropriate amount of viscosity reducer to lower viscosity while maintaining fluidity and color reproduction. Filter the ink through a filter screen of 150 mesh or above to remove impurities.

Match materials: Promptly replace plates with worn or deformed dots. Choose high-quality paper with a smooth surface and minimal dusting/linting, and condition paper for 24 hours before printing. Reduce coating amount or replace paper for poor ink absorption.

Adjust process: Regulate ink fountain roller speed to reduce ink coating. Calibrate printing pressure to lower contact pressure between blanket, plate and paper. Maintain drying equipment at 80–100°C with matching wind speed to ensure thorough ink drying.

• Pitfall Avoidance Reminder

Avoid three improper operations: blind addition of diluent (worsens blinding; use viscosity reducer instead); excessive increase of printing pressure (causes ink overflow and plate wear; calibrate pressure); neglect of plate cleaning (leads to impurity accumulation; clean plates regularly).

(3) Strike-Through: Causes and Prevention Techniques for Offset Printing Ink Penetration

• Cause Analysis

Offset printing ink characteristics: High transparency, weak tinting strength, low solid content or excessive fluidity lead to easy ink penetration into paper.

Paper factors: Paper weight below 80 g/m², loose fibers or poor compactness; excessive ink absorption or insufficient surface sizing cause ink penetration or strike-through.

Process issues: Excessive ink coating, overhigh printing pressure or excessive overprinting accelerate ink penetration and accumulation.

• Practical Solutions

Select offset printing ink: Choose ink with solid content ≥50%, high tinting strength and low transparency. Add opaque agent to highly transparent ink for better coverage. Add a small amount of thickener to reduce fluidity.

Match paper: Select book paper of 80 g/m² or above and packaging paper of 120 g/m² or above. Choose paper with uniform sizing and moderate ink absorption. Laminate or prime the back of thin paper to block penetration.

Control process: Determine the optimal coating amount via trial printing. Reduce printing pressure. Optimize overprinting order (light colors first, dark colors later). Extend drying time to ensure thorough ink drying.

• Detection Methods

Back Observation Method: Place the sample on a white background-clear patterns visible on the back indicate severe strike-through, while faint traces indicate mild strike-through.

Weighing Method: Compare the weight difference of paper before and after printing; an excessive difference signals excessive coating.

(4) Supplementary Notes on Related Faults

Ink smudging and dot gain are common secondary faults. Smudging is mostly caused by plate blinding or slow ink drying, leading to ink adhesion when printed materials are stacked. Dot gain often results from ink misting or excessive pressure, causing blurred dots due to ink splattering. These faults can be resolved by optimizing processes as outlined for the three core faults.

Practical Mnemonic:Tune viscosity for misting, anti-misting agent lends a hand;Calibrate roller pressure, control temp and humidity well;Cut viscosity for blinding, fast-drying ink works best;Clean dots regularly, avoid overpressure;Pick thick paper for strike-through, high solid ink is wise;Control coating amount, ensure good coverage.

(1)Pre-Printing Prevention

Conduct compatibility trial printing of offset printing ink, paper and plates before mass production, and confirm no faults before formal production. Clean rubber rollers, ink fountains and plates regularly; calibrate roller pressure and ink viscosity weekly, and conduct comprehensive equipment maintenance monthly. Formulate standardized parameters for speed, pressure, coating amount, temperature and humidity to avoid arbitrary adjustments.

(2)In-Production Troubleshooting

Inspect samples regularly: sporadic ink spots indicate misting, blurred layouts signal blinding, and back ink penetration points to strike-through. Watch for abnormal equipment noise and shut down the machine promptly if anomalies occur. Assign dedicated staff to inspect ink, equipment and printed materials every 30 minutes to prevent fault escalation.

(3)Post-Production Summary

Establish a fault log to record the time, machine model, consumables, symptoms, causes, solutions and effects of each fault. Analyze the log regularly to optimize preventive measures. Organize staff review and training to improve the team's fault response capabilities.

The core of resolving offset printing ink faults lies in accurate cause identification and targeted solutions. The three major faults essentially stem from the imbalance of offset printing ink, equipment, process and environment. Enterprises should focus on consumable compatibility and implement full-process prevention and control. It is recommended to strengthen staff practical training, establish ink process compatibility standards and enhance equipment maintenance. Procurement personnel should prioritize offset printing ink from regular manufacturers and conduct trial printing before bulk procurement. For recurring complex faults, contact suppliers for customized solutions to achieve high-quality and low-cost production.