All the pinakryptol dyes are desensitizing agents (although there are some differences between them - some are destroyed by sulfite and have to be used as a forebath etc).(posted 8256 days ago)The purpose of pinacryptol yellow in FX2 is as a restrainer. Something about slightly better discrimination between exposed and unexposed grains, if I'm remembering Anchell and Troop correrctly. In my experience, it never made much of a difference. Its a pretty clean working formula. Cheers, DJ.