UV Printing Troubleshooting: Questions and Answers
3.Ink Defect
| No. | Item | Printing System |
Phenomenon/ Situation |
Explanation | Cause | Counter-measure |
| 301 | Ink Defect (gelation) | All System | The ink stored has undergone hardening. | Ink hardening or gelation. UV inks inherently cure not only through ultraviolet lay but also through catalysts and heat. This issue is particularly prone to occurring when dampening water, paper dust, or metallic inks (e.g., silver) are mixed in. Metallic special inks are especially susceptible to such problems. | Ink defect due to storage conditions. |
A) Discard gelled ink that past its expiration date. If gelation occurs within the expiration period, consult the ink manufacturer. B) Discard any leftover ink that may have been contaminated with foreign substances. C) Recommend storing metallic inks in the refrigerator. D) Metallic special colors should be used as quickly as possible to avoid issue. |
| 302 | Ink Defect (color variation) | All System | The special color ink produced and stored in-house, has experienced the color variation by passage of time. | This issue is attributed to the properties of the pigments. Special caution is necessary when using inks with low resistance, such as warm red, fanal series inks, or fluorescent inks, as color fading may occur due to the influence of the UV vehicle. Particular attention should be given when using inks for complementary colors. | Characteristic of the pigment and incorrect ink selection. | To use lightfastness inks. When selecting inks for complementary colors at concentrations of 5% or less, important to ensure that inks of super-lightfast or higher ratings should be used. |
| 303 | Ink Defect (Poor flow) | All System | Insufficient ink flow, leading to sitting back phenomenon. | Owing to its composition and formulation, UV ink tends to have a lower flow in comparison to other inks and is more susceptible to the "sitting back" phenomenon. This issue may be further exacerbated in offset printing, particularly due to the emulsification process. | Poor flow |
A) Mix well before use B) Reducing the viscosity by adding a reducer C) Install agitator or mixer D) Ask to ink manufacturer. |
| 304 | Ink Defect (Separation) | Flexo | The pigment had accumulated at the bottom of the ink container while using UV flexo opaque white ink. | Low viscosity flexo inks are prone to cause pigment separation. Special attention is required, particularly for white inks with a higher pigment density. Additionally, additives with a lower specific gravity may also be happened additive separation. | Ink usage | When using flexo ink, always ensure to thoroughly mix the contents, such as by shaking the container before use. |
| 305 | Ink Defect (Gelation on fluorescent ink) | Fluorescent P Series | Stored fluorescent ink or mixing ink using fluorescent P ink and standard UV ink gets harden. | In the case of the Fluorescent P Series, the use of an oil-based fluorescent base in its composition leads to compatibility challenges with the UV vehicle, which results in a tendency for the ink to thicken more readily. However, unlike the gelation observed with standard UV inks, it is generally possible to restore the ink through appropriate re-adjustment. | Compatibility failure |
A) Fluorescent ink hardened can often be made usable by thoroughly stirring it with a dedicated reducer (UV fluorescent reducer). For other cases, consult the ink manufacturer." B) When producing special fluorescent color inks, recommend using up as soon as possible. |