In the process of irradiation, mail is exposed to extreme heat. Paper is weakened and may appear to have been aged, with discoloration (e.g., yellowing), and brittleness. Pages may break, crumble, or fuse to other pages. Documents bound with glue may have loose pages. The printing on pages may be distorted or offset onto adjacent pages. If tape is affixed to address labels, the address may be illegible.
Materials other than paper may also be affected. Plastics and inks may melt and fuse. Irradiation can affect such enclosures as photographic films, transparencies, and prints; compact disks, audio cassettes, and electronic, digital, and magnetic media; compact disk jewel cases; and credit cards.