What can cause silicone to turn yellow?

Silicone turning yellow is pretty common over time, and it usually comes down to a mix of environmental and chemical factors rather than a single cause. Here are the main culprits:

1. UV exposure (sunlight)
Silicone itself is fairly UV-resistant, but not immune. Prolonged exposure to sunlight can break down additives in the material, leading to a yellow tint. This is one of the most common reasons, especially for outdoor or window-exposed items.

2. Heat and aging
High temperatures or long-term heat exposure can accelerate oxidation. As the silicone ages, chemical changes in the polymer or its additives can cause discoloration—often yellowing.

3. Oxidation
Oxygen in the air slowly reacts with certain components in silicone (especially fillers or curing agents), which can lead to a yellow hue over time.

4. Contamination (oils, smoke, chemicals)
Cooking oils or grease
Nicotine/tobacco smoke
Air pollutants
Cleaning chemicals

These can either stain the surface or chemically interact with it, causing yellowing.