Ammonium sulfide is a pungent but essential chemical used in photographic sulfide and sepia toning processes. It reacts with silver in black-and-white prints to produce warm brown or sepia tones, enhancing the aesthetic appeal and archival stability of the image. Photographers and darkroom technicians use ammonium sulfide carefully, as its strong odor and chemical reactivity require proper ventilation and handling precautions. Mastery of ammonium sulfide toning allows for creative control over print coloration, adding depth, richness, and longevity to traditional photographic prints.