What causes this with tipped in photos in book?

 

Is there acid in the photo?

I suspect residual chemicals that were not completely washed out.

There is a balancing act, you need to wash enough to stabilize the print, yet you don't want to wash too much and damage/weaken the paper.

The later RC (resin coated) papers reduced the chemical penetration into the paper, so washing was easier.

I suspect residual chemicals that were not completely washed out.

There is a balancing act, you need to wash enough to stabilize the print, yet you don't want to wash too much and damage/weaken the paper.

The later RC (resin coated) papers reduced the chemical penetration into the paper, so washing was easier.

 

I should have been clearer. These are litho prints in the book. Just glued on one edge, so not glued all over to cause the problem.

Then maybe the ink that was used to make the print is leaching out a chemical to discolor the facing page.

Mechanics? The image looks pre-"lets clearcoat everything!"-days in the printing industry. So some never really drying pigments are on top of paper. Handling and compressing the book can smear them on the opposite page.

I don't think this is "smearing" so much as it is, as noted, chemicals in the ink outgassing.

Maybe a stupid response, but to me, it doesn't look as if the photo and text are on the same plane (scan, photo). Perhaps it was impossible to do so. Most things can be corrected or enhanced in PP.