4 Common Misconceptions in Adjusting Offset Printing Ink Suitability

Posted on 04-15-2024 by

During production, it is often necessary to adjust the suitability of the ink used to meet the printing needs of different products and paper types. Adjusting ink suitability is achieved by adding appropriate additives to the ink. Due to varying understanding or biases towards additives, it is possible to fall into certain "misconceptions" during actual production, resulting in unsatisfactory outcomes.

1. Substituting Anti-tack Agent for Ink Adjuster

During production, when printing large solid areas, ink may not be evenly distributed on the ink rollers or may cause phenomena such as paper "picking" or rough prints. This is generally due to excessive ink viscosity.

Both anti-tack agents and ink adjusters can reduce ink viscosity, but they have different properties. Anti-tack agents not only reduce ink viscosity but also inhibit ink drying and reduce ink adhesion to the paper. Ink adjusters, on the other hand, primarily reduce ink viscosity and increase ink flow in the ink, with minimal impact on drying speed.

Adding excessive anti-tack agents to reduce ink viscosity may lead to "tacky printing" or ink layer "powdering." Therefore, caution should be exercised in the amount of anti-tack agent added, keeping it within the appropriate range, while increasing the amount of drying agent to avoid adverse effects.

2. Using White Ink as a Diluent

Some colored inks need to be diluted with a diluent to become lighter. This diluent should be colorless and transparent. Gloss varnish and varnish are ideal diluents as they do not change the color of the original ink but alter its intensity. Using white ink as a diluent is inappropriate because white ink changes the color of the original ink, making it tend towards a pale jade color rather than becoming a lighter ink.

This contradicts the operator's need for lighter ink. Additionally, excessive white ink in the ink mixture can lead to rough prints due to the higher density of white ink particles, causing them to accumulate on the printing plate or rubber blanket during ink transfer.

3. Failure to Distinguish between Anti-tack Agents and Ink Adjusters

Adding anti-tack agents to ink prevents or reduces the problem of ink sticking to the back of the printed paper, while ink adjusters reduce ink viscosity, mainly during the ink transfer process. Failing to distinguish between the two may lead to other issues.

For instance, adding an ink adjuster to prevent ink sticking to the back of the paper may inadvertently prolong drying time and increase the likelihood of paper surface contamination. Conversely, adding excessive anti-tack agents to reduce ink viscosity can result in ink "coarsening," leading to loss of gloss and affecting product quality.

4. Neglecting the Difference between Red Driers and White Driers

Though both red driers (also known as tung oil) and white driers (also known as driers) are drying agents for ink, their compositions result in different drying effects on the ink layer.

Red driers accelerate surface oxidation and drying of the ink layer, while white driers promote overall ink layer drying. Therefore, it's essential to consider their differences in drying behavior. For surface drying, red driers are preferable.

However, when dealing with thick ink layers or papers with poor inherent drying properties, using only red driers may lead to a state where the ink surface is dry but the interior remains wet, affecting product quality when subjected to friction. Moreover, when printing with gold or silver inks that require drying agents, red driers are preferred over white driers, as the latter can darken the original ink color, affecting the metallic luster of the printed product.