What is light fastness? Light fastness describes how well an ink or coating resists fading when exposed to light. It matters wherever packaging sits under retail lighting or in a window for weeks, because the pack is the brand at that point, and faded artwork reads as old stock.
Why do some colors fade faster? Different pigments have different stability. Bright magentas, oranges, some fluorescents and certain metallics tend to move first, while carbon black and most earth tones are comparatively stable. If one brand color is critical, ask about that specific ink rather than about the job as a whole.
How is it rated? The blue wool scale runs from one to eight, with higher numbers indicating better resistance. Ask which rating the specified inks carry and judge whether it suits where the pack will sit. Ink families and their behavior are compared in the printing inks explanation.
Does a finish help? A film or coating over the print slows fading by filtering some light and adding a physical barrier, though no coating stops it indefinitely. UV-cured coatings behave differently from water-based ones, and some shift color slightly when applied. Options are compared in the varnishing guide.
What about yellowing? Yellowing is a separate issue, usually linked to certain coatings as they cure or age, and to board exposed to heat or sunlight over time. White and pale artwork shows it most clearly. Storage conditions matter as much as the material itself, as set out in the box inventory guidance.
How is exposure tested? Samples are exposed to a controlled light source, sometimes combined with heat and humidity cycling, then compared against an unexposed reference. It is slower than most buyers expect, so it needs booking into the sampling schedule rather than being added at the end.
What should you do about it? Tell the supplier where the pack will be displayed, ask for light-fastness ratings on critical colors, and consider a protective finish if display is in direct sunlight. For long shelf life, keep a reference sample stored in the dark so any drift can be measured against something.
Chengtop prints and finishes at our Wuhan plant, producing cosmetic packaging, علب هدايا صلبة and retail cartons. Tell us where the pack will be displayed through the quote request page and we will come back with a quote.
