Why prints fade, stain and crack
The Northeast Document Conservation Center explains that in colour prints the cyan dye usually fades first, leaving a reddish tinge; many early colour photos lost about 30% of their dyes within 10–15 years [1]. High humidity drives fading, discoloration and silver mirroring, and chemical decay roughly doubles with every 10°F rise in temperature [2].
What the repair tools actually do
Photoshop's Healing Brush paints with a sample to repair imperfections and the Patch tool repairs a selected area from a sample [3]; Dust & Scratches removes specks by changing dissimilar pixels within a radius [4]. GIMP's Heal tool does the same kind of repair, taking surrounding pixels into account [5]. AI restorers go further by rebuilding faces from a learned face prior, as research models like GFPGAN do [6] — faster, but a guess where damage is heavy.
The archivists' rules for your files
The US National Archives recommends keeping originals after scanning and following the 3-2-1 rule — three copies, two media, one off-site [7]. The Library of Congress adds: check your photos at least once a year and copy them to new media every five years [8]. Keep the untouched scan as your master; restore a copy.
