How does carbon reduce tin oxide to tin metal during smelting?

The principle of tin smelting relies on the chemical reduction of tin oxide. During this process, tin oxide concentrate is heated in a furnace alongside carbon, typically in the form of anthracite coal or coke.1

As the mixture is heated to high temperatures—often between 1,300 and 1,400 °C in a reverberatory furnace—the carbon acts as a reducing agent. In this reaction, the tin oxide releases its combined oxygen, which then recombines with the carbon to produce tin metal and carbon dioxide gas. This process effectively separates the metal from its oxide form, allowing the resulting molten tin to be collected while impurities are removed as slag.12