For instance, aluminum mirrors are commonly coated with silicon dioxide or magnesium fluoride. Additionally the barrels are nitride coated for corrosion resistance. Wooden furniture was often coated with a layer of plaster and painted. The glass is also sometimes coated with polymers. The cracks may be coated or filled with soil material. It is coated with wax to repel water. Another advantage is that the brazing can be coated or clad for protective purposes. The pistons were coated with molybdenum to reduce friction. This fondant can readily be coated with dark chocolate. These pieces are typically coated in chocolate and sold individually. It is usually coated and decorated with frosting. After the image is defined, the material must get coated with soldermask for later soldering. Originally forged from iron, it has since been coated in bronze. The rock reliefs were probably coated in plaster and painted. It is sometimes first coated with flour.