Coal obtained through dry distillation or incomplete combustion of wood with a C content of more than 80%. In foundries, charcoal is used both as a reducing covering agent, especially for melting copper and copper alloys, and as a powdered mold material additive and carburizing agent for case hardening.
When burnt under air, charcoal converts to CO and CO2. These two oxides are present in a temperature-dependent equilibrium (see Boudouard equilibrium). As a covering agent for the melting of copper and copper alloys, charcoal has an absolutely reducing effect since only carbon monoxide is produced by combustion at temperatures of over 1000°C. The melting and superheating under charcoal is also referred to as non-oxidizing melting and results in minimum weight loss due to oxidation.