Here is a question from the ultimate lurker...why did my work done in Lyra Rembrandt Polycolor CP fade drasticallyafter 3 weeks? It has not sat in direct sunlight. It was also drawn on Stonehenge paper. I used colors that should have the greatest lightfastness.

Karen

Good question. Perhaps you could scan the picture for us to look at. It could be what you think is fading of the pencils, is actually something I have noticed before also with stonehenge paper. It's hard to explain, because I don't know what is happening really, but it looks as if some of the brightness of color pigment disappears or sinks into the paper over night, and you see white bumps of the paper appear. This has happened to me before, but when I then burnished and immediately sprayed the piece it looked better again.
Post a close-up picture of your work for us to see. Perhaps someone then can help you better. ;o )

I don't know Poly chromos, but prismas will get a wax bloom if not sealed.
I take a cotton ball and carefully wipe it, then spray.
Christine is right you should put up a picture.