Okay, so I figure I'll rescue my collage by cutting out the enneagram part and gluing it to a new piece of background paper. This time, I decided to spray the paper first--and, lo and behold, it came out splotchy, which leads me to think that maybe the solvent is interacting with the paper--I haven't seen this happen with the images I've been cutting from magazines. So, I found another piece (I bought a bunch of 12 x 12 colored paper at a yard sale a few weeks ago--and have coated it with matte polymer--which is still too shiny. But, if I spray that, I think it will take off the shine without screwing up the paper---maybe.
My other option is to paint the paper that the enneagram is currently on.
I think I'll go back, in the future, to not trying to use plain background paper. Seems like more trouble than it's worth. ------ In my city walkabout I encountered a Goth yardsale, where I bought a copy of the Dalai Lama's four noble truths book. Cost me $.25/truth. Also found Ouspensky's "In search of the miraculous" at Half Price--I've been looking for that sucker for at least a year now, figuring it would turn up eventually.