The main culprit is an organic compound that goes by the name of anti-ozonant. Anti-ozonant is added to rubber and plastic materials to prevent oxidation, fading, cracking, and premature degradation.

Anti-ozonant is constantly drawn to the surface to constantly protect the material from oxidation caused by repeated and constant exposure to UV damage, high temperatures, dirt, and mud.

You can think of it this way: anti-ozonant is like applying sunscreen lotion on your skin when you’re out all day on the beach. Without sunscreen, you will burn to a crisp in less than 2 hours.

Anti-ozonant will serve to protect and prolong the life of the tire. Without it, you will need to constantly buy new tires as UV damage and heat will significantly shorten the lifespan of the rubber compounds in your tire.

But there’s a catch. When the anti-ozonant is exposed to air and moisture as it is drawn to the surface of the tire, it oxidizes and leaves a brownish residue. This is the main cause of tire blooming.

Tire blooming can also be partly blamed for lubricant-type chemicals that are applied in the manufacturing process, particularly in the inside of the tire mold. Think of it as a non-stick coating that allows the tires to release smoothly from the tire mold.

This non-stick coating will chemically bond with the tire in such a way that it holds a lot of anti-ozonant on the surface of the tire. You know what that means, right? As more of the anti-ozonant is drawn to the surface of the tire, then more of it will oxidize and cause those ugly brown stains on the tire sidewall.