Every once in a while we get a call from someone whose poster has faded over a period of time.
What causes this is the impact of ultraviolet light on the inks. If your poster is in a window or gets direct sunlight, that will do it. There are also some kinds of interior lighting that can be problematic. Almost any kind of printing will fade in sunlight, not just our inkjet printing.
We have prints that have been up in our shop for over 10 years, and they still look great. We have also had some that are very close to fluorescent lights that have faded. It really is a matter of the conditions under which the prints are displayed. We also find that lamination helps to protect the print from UV as well as fingerprints.
If you are hanging your poster in a lab that gets a lot of sunshine, we would suggest that your order your print with UV stable inks. They will not fade for years even in direct sunlight. It adds 10% to the cost.
Unless your prints are getting direct sunlight, it’s probably not necessary to pay the extra for UV inks. We don’t use them as a matter of course because of the increased cost, and the fact that colors are not as accurate with UV inks.