Any metal sculpture, whether it is bronze or another metal, will likely change in appearance over time. A number of factors can affect the way a metal sculpture ages. These include:

• Environmental factors (for example, humidity, exposure to salt air, extreme sunlight, handling, and contact with water and/or chemicals). A good maintenance program is the best way to guard against further undesired changes to patina and possible metal corrosion.
• The original patina and finish. Some of the chemicals used during the patination process hold up better over time and in certain conditions than others. For example, the chemical that produces a white patina is fairly unstable and is not suitable for sculptures that will be installed outside, and a red patina will often darken or fade over time. Regardless of the type of patina used, any sculpture must be well sealed after patination (with either wax or lacquer). This finish must be maintained to preserve the underlying patina.
• Proper maintenance. If a bronze is properly maintained over time, it should age nicely and restoration should not be required. However, if a sculpture is left unattended for a period of time, it might collect layers of dust, dirt, or chemical/mineral build up that should be removed to preserve the patina and prevent possible corrosion.