I was told by a helpful lady at my lss that when in doubt, you should color copy the item onto card stock. I tried this with newspaper pictures and articles, and ticket stubs and playbills. It looks just like the original and after several years no yellowing or darkening. I put the originals away, some place dark and use the "fakes" in my scrapbooks. I was told to be sure to color copy--even newspaper--because that ink is more stable.
HTH Deb