Unhardened emulsions are easily scratched when wet, and absorb moisture when dry. Adding Sprint RECORD Alum Hardening Converter to a fixer solution is one method of toughening emulsions to be more resistant to abrasion and water absorption. If used correctly, it will increase archival permanence by protecting emulsions.
Resin-Coated Prints require alum hardening converter to prevent scratching, and for a hard gloss on glossy finish papers.
Fiber-Based Prints should only be hardened if prints are to be dried on hot drums, or if emulsion is very soft. Fiber prints are hardened during manufacture, as well as by exposure to heat, light, and air, so additional hardening may be harmful.