Blooming is a common quality problem in rubber processing. It refers to the migration of the unvulcanized rubber or the coordination agent contained in the vulcanized rubber to the surface and precipitation. Sometimes, this ejecta is a frost-like crystal, so it is customarily called "spray frost". 

The most common frosting substance is sulfur, because sulfur is the most widely used vulcanizing agent in general rubber, and it is easy to produce frosting because of its low solubility in rubber. In fact, from ejecta appearance, also may not be frost, also have oil (softener, plasticizer) or powder granular (for filling agent, anti-aging agent, promoting agent) material ejecta, even carbon black ejecta also see.