Help! Canvas prints turning green...

[Lionheart]

In my dental practice, we use our photo studio to take portraits of our full mouth regenerative case patients to show all around the office, particularly in the reception area. This is something we've only recently started doing in the past year. We've been shooting digitally, converting to black and white and printing 18x20 on canvas framed on a stretch frame. We've been using a local printing service that prints them using a very largish and professional looking epson printer that the owner assures me is very archival. However, under the halogen lighting that we spotlight the photos with, they're turning green over a relatively short time. The smaller prints (8x10) that we've printed on our dye sub printer in office have done just fine under the same lights. Is there a better alternative to printing digital photos on canvas besides using inkjets? Any help would be GREATLY appreciated.

[FREELANCE2004]

i thought moisture caused this type of problem.read that awhile back somewhere.dont know how true it is ,but makes since,the material subject to humidity and so forth .if its in a doorway or by a ac vent.
let me know.