text: Sulfur bloom refers to the migration of sulfur, usually as S, to the surface of a rubber article either before or after vulcanization.  Blooming is undesirable in rubber processing.  When sulfur bloom appears before vulcanization, the rubber is deprived of the crosslinking agent. Sulfur bloom after vulcanization indicates incomplete vulcanization. In rubber processing, ingredients other than sulfur can "bloom", including antioxidants, fatty acids, and accelerators.