All of these clocks take Alkaline AA batteries, which can be bought anywhere and will last approximately one year before needing to be replaced. Depending on the style of clock you choose, there is a real layer of either bronze, copper, or pewter metal. Overtime the clocks will develop a natural patina just as any bronze or copper metal might. While most gardeners like the aged look, the clocks can also be cleaned by using any metal polishing solution.