Your favorite white sneakers, like Adidas Stan Smiths, turn gray over time, and not just because of dirt. The main culprit is an invisible chemical reaction known as oxidation, which...
Your favorite white sneakers, like Adidas Stan Smiths, turn gray over time, and not just because of dirt. The main culprit is an invisible chemical reaction known as oxidation, which breaks down the polymer materials of the sole and upper.
The sun's ultraviolet radiation and oxygen constantly attack materials like the EVA foam and polyurethane used in the Nike Air Force 1 soles. This process, called photodegradation, alters the chemical structure of the fibers and their color.
This is why white Air Max 90s or Converse All Stars often turn yellow first and then develop a persistent gray tint, especially at the flex points. This is similar to how old plastic items or car tires lose their original appearance.
Some manufacturers, including Puma and Reebok, add special UV stabilizers to rubber to slow down the degradation process. However, over time, even titanium dioxide, used to create the white color, can lose its properties when exposed to the environment.
It's nearly impossible to completely reverse the darkening, as it's a structural change, not just surface dirt. To slow down the process, store your shoes in a dark place, away from direct sunlight, and use special care products.
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