Blooming in scientific terms means the migration of some of the compounding additives to the rubber surface when their concentration exceeds their solubility limit in that rubber matrix.

Major Reasons for Blooming in rubber are: Excess dosage of Sulphur, heat, prolonged storage.

How to Prevent Sulfur Blooming

To prevent sulfur blooming, Insoluble sulfur is added in rubber instead of Sulfur or RMS, where Dosage is usually more than 1.5 PHR. Sulfur blooming affects rubber quality.

Since the tyres have higher volumes of metal; It requires strong rubber to metal bonding. Also, the thickness of compounds is very less: the probability of blooming increases. 

Hence a higher dose of Insoluble Sulphur is used.

In general, Insoluble sulfur is added instead of Sulfur or RMS to prevent blooming, where Dosage is usually more than 1.5 PHR.