Hierarchy classification:

1. top of the aat hierarchies
2. Activities Facet
3. Processes and Techniques (hierarchy name)
4. [processes and techniques by specific type]
5. condition changing (processes)
6. color changes

Anotations

Scope note:

A deteriorative process affecting silver photographic images, in which the silver reacts with sulfur from the air or from within the print itself to form silver sulfide, causing the print to yellow and fade.