Sulfiding treatments are a way of protecting black & white prints against oxidative attack. The sulfiding ingredients are in fact responsible for most of the protection imparted by dilute selenium and gold toners, compounds that form a layer of silver sulfide at the surface of developed silver grains.
The use of Kodak Brown Toner gives complete protection, even when used in a diluted solution. Kodak Brown Toner does its work of protecting the image silver without significant change of density or image hue. One of the most positive aspects of sulfiding treatments is that they are cheap and pose less environmental hazard.
Though many silver images have been ruined by poor processing, i.e., improper fixing and washing, a more important deterioration mechanism for the majority of photographs is image oxidation. Black & white photo collections are especially vulnerable to the form of oxidation known as “red spots,” and outbreaks of this problem are becoming more frequent and severe. Archival processing for all types of silver images include sulfiding treatments to resist oxidation.