Two forms of iron are used in iron clocks. One is cast iron, which is hard and can be brittle owing to its high carbon content. Cast iron was used on the front of some antique clocks and enameled with black for the clock cases. Wrought iron is softer and can be worked (wrought) with a tool to expel the impurities and to create more decorative pieces. Often the wrought iron was covered with a charcoal gray, antique bronze, or