A must-read for workshop staff! The most common high-frequency failures in offset printing production!

A must-read for workshop staff! The most common high-frequency failures in offset printing production!

In offset printing, workshop staff have experienced this firsthand: ink mixing, machine use, and color inspection are never a one-time solution by simply formulating formulas. Even if the ink mix ratio is repeatedly checked for accuracy, various printing issues will still arise after machine use. In this article, the author has compiled some frequently encountered issues during offset printing, hoping to provide some reference.



The back is stained



Symptoms: Ink drying that is too slow, too soft, too thin, or too large in ink can easily cause ink to rub against the back of the previous page, resulting in paper sticking, commonly known as "paper biting."



Cause analysis: Besides the ink's own characteristics, improper use of fast-drying ink, printing double-sided smooth paper, large ink feed at the dotted area, and environmental static electricity can all cause back smudging issues.



Solution: (1) Minimize ink supply as much as possible while meeting production requirements; Apply appropriate pressure to rough paper. (2) Use quick-drying ink or use high-concentration ink to reduce ink supply. (3) Test before replacing with new ink; during color registration printing, add more desiccants for the last color, anti-stick additives, or powder spraying.



Flying ink



Phenomenon: Fine ink particles are scattered from the running printing press, seriously affecting the workshop environment and print quality.



Cause analysis: The faster the printing speed, the thicker the ink layer, the longer the ink filaments, poor ventilation, and low humidity increase static electricity, causing ink to fly more severely.



Solution: (1) Add covers to the ink leveling roller and ink transfer roller, or install mechanical devices on the machine stick to prevent ink particle flying. (2) Increase workshop humidity, lower temperature, or increase ventilation to eliminate airflow. (3) Use conductive water emulsification ink, or add binder to the ink.



Do not use ink



Phenomenon: The ink does not rotate with the ink roller on the machine, resulting in a lighter and uneven color tone of the printed product.



Cause analysis: Excessive pigment content, ink that is too thick or too short to form a cheese-like texture, or excessive acidity in the chemical solution causing emulsification of the laminating liquid, all of which can cause ink to come off the roll.



Solutions: (1) Add a thinner or medium-viscosity binder to increase ink flowability; (2) Add a small amount of wetting agent; (3) Reduce the amount of dampening solution used during offset printing, or add a thicker binder or diluent to the ink.



Paste plate



Phenomenon: Ink stains appear in non-image and text areas, text is filled into solid areas, and dots merge into a continuous seam.



Cause analysis: Ink stickiness is too high, dry skin in the ink bucket, too thin ink absorbs too much binder, uneven surface surface, low water acidity or insufficient water volume, etc.



Solutions: (1) Add diluted ink to the ink, or switch to quick-drying resin ink to reduce the oil and grease content in the formula. (2) Apply the plate at high-pressure areas to reduce pressure; Select the appropriate ink based on the paper; Check the acidity of the dampening solution; Increase the water supply or use a solution with high surface tension.



Transparent back/transparent printing



Phenomenon: Ink penetrates the paper too deeply, making the pattern or text printed on the back clearly visible.



Cause analysis: Ink is too thin, too oily, too permeable mineral oil, and dries too slowly.



Solution: (1) Accelerate ink drying, or use dry oil and high-quality mineral oil in the ink; (2) Thicken the ink a bit or add a small amount of silicone additives to increase resistance.



Pile up ink



Phenomenon: Ink accumulates on the printing press, pigment appears as a separated powder, dots are soggy, and colors are inconsistent.



Cause analysis: poor ink dispersion, use of dense, coarse-grained inorganic pigments, too thick ink film, or poor ink roller function.



Solutions: (1) Check whether the equipment pressure, ink roller function, and pads are normal. (2) During production, the amount of ink supplied should be appropriate; if too soft, thicken it. If there are no issues, add medium-viscosity or thin ink adjustment to the ink, preferably replacing with new ink.