Clean and polish bronze by applying a paste made from lemon juice and baking soda to the entire surface of the piece, allowing it to dry and then removing the paste using a small polishing cloth. If the green coating on the piece is especially thick and difficult to remove, you may have to apply several successive coats of paste to fully remove the coating.
The amount of baking soda and lemon juice to use depends on the size of the bronze piece being cleaned. For most small pieces such as candlesticks or bowls, start with about 2 tablespoons of baking soda. Slowly drizzle lemon juice onto the baking soda, until you have enough liquid to form the powder into a paste. The mixture will fizz slightly at first due to the reaction between the citric acid in lemon juice and the baking soda, but this will subside quickly.
Be careful when considering whether or not to clean antique bronze pieces that have acquired a greenish brown coating. This coating is called patina, and while some find that it looks unsightly, it actually protects the bronze underneath. Furthermore, collectors of antique bronze always prefer that pieces retain their original patina. Cleaning an antique bronze piece may improve its appearance, but it can have a serious negative effect on its value.