I did a bunch of autotracing of rubber stamped images today (stamped on heavy card stock), and some of them have a bit of smoke stains on the edges.
Thought I’d show my method for getting most of the stains off: bleach on a pointy cotton swab (I got these from the local Sally’s Beauty supply, they are for nails).
Although it doesn’t always get all traces of smoke stain off, usually the improvement is significant.
You wouldn’t want to do this on paper used for long term archival purposes, I imagine bleach is pretty hard on the paper fibers. Works fine for card making though.