A customer has complained that a poster is fading almost immediately with exposure to sunlight. The fading is particularly bad in yellow. Why is this?

The likely cause is that the yellow ink was made with diarylide pigment. Diarylide is a brilliant yellow pigment that has poor fade resistance from the UV rays in sunlight. Ink pigments will eventually fade when exposed to sunlight; how rapidly they fade depends on the pigment (yellow and magenta pigments fade fastest) and the amount of exposure (heat and humidity also play a role). Make sure to find out how customers will use printed pieces and, in cases of significant exposure to sunlight, use fade resistant inks and a varnish or lamination with UV inhibitors.