Lightfastness standards for offset printing inks

Lightfastness standards for offset printing inks are divided into five-level and eight-level systems
‌Lightfastness standards for offset printing inks vary depending on the region and application requirements, and are mainly divided into two systems: the five-level system of the Chinese national standard (based on lightfastness duration) and the eight-level system (blue wool scale) commonly used in the international/industry. ‌

Specific standard comparison
‌Chinese national standard (five-level system)‌
According to the search results, the domestic standard divides the lightfastness of offset printing inks into five levels, based on the duration of UV resistance:

Level 1: Resistance <30 hours
Level 2: 30~50 hours
Level 3: 50~80 hours
Level 4: 80~100 hours
Level 5: >100 hours (highest level)

The applicable standards for different color inks are also different:

European market requirements: red and yellow inks must reach level 5 or above, black and blue must reach level 7 or above.
Asian market (such as Japan): The lightfastness level of yellow and red inks is usually only about level 3.
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International/High-end Product Standard (Eight-level System)‌
The search results show that light fastness can also be divided into 1~8 levels (8 is the highest), which is common in professional outdoor inks:

Ordinary inks: black and blue sun protection levels are usually ≥5, red and yellow ≤3.

Professional inks: black and blue can reach 7~8 levels, red and yellow can reach 5~8 levels.

Application scenario differences: Level 6 corresponds to outdoor half a year, level 7 1~2 years, and level 8 2~3 years.

Detection and influencing factors

‌Detection methods‌: including ultraviolet radiation testing, colorimeter evaluation, etc., which need to be combined with specific standards (such as QB/T 2624-2012, HJ 2542-2016, etc.).

‌Key factors‌: In addition to the ink itself, the light fastness of the substrate also directly affects the final effect. If the substrate is easy to fade, the printed pattern will also change color.
It is recommended that when selecting ink, a comprehensive judgment should be made based on the actual application scenario (such as outdoor time, light intensity) and regional standards, and a light fastness test should be conducted in advance.