Bronze sculptures are admired for their timeless beauty, but over time, they often develop discoloration due to various factors. The most common causes include oxidation, environmental exposure, and improper care.

1. Oxidation and Patina Formation: Bronze naturally reacts with oxygen, forming a green or brown patina. While some patina is desirable for its protective layer, excessive oxidation can lead to uneven discoloration.

2. Environmental Factors: Pollution, humidity, and saltwater exposure accelerate corrosion. Acid rain and airborne chemicals can cause dark spots or streaks on the surface.

3. Improper Cleaning or Maintenance: Harsh chemicals or abrasive cleaning methods strip the protective patina, exposing the bronze to further damage and discoloration.

4. Biological Growth: Algae, moss, or lichen can grow on outdoor sculptures, leading to green or black stains that penetrate the metal.

5. Metal Alloy Reactions: Impurities in the bronze alloy or contact with other metals can trigger galvanic corrosion, resulting in blotchy discoloration.

To preserve bronze sculptures, regular cleaning with gentle solutions and protective wax coatings is recommended. Understanding these causes helps collectors and conservators maintain the integrity and aesthetics of these cherished artworks.