Rubber cement is never safe for photos.
Acid-free products should have a pH factor of 7.0 to 8.5. Acid Migration - Acid can transfer from one item to another through close physical contact or even from contact with oils in human hands. Newsprint will cause paper to discolor, so any newspaper announcements or articles should be photocopied. Copy onto off-white paper that resembles the color of newsprint for an authentic look. Archival Quality - Archival quality materials have undergone analysis to determine that their acidic and buffered content is within acceptable levels.