A mass of solid aluminium carbide containing product is produced by injecting particulate alumina into a bath (30) of molten aluminium metal; and injecting carbonaceous material, consisting of, containing or yielding carbon, into the bath (30). The bath (30) of molten aluminium metal is maintained at a superheated temperature to heat and react carbon with molten aluminium to produce solid aluminium carbide which mixes with alumina to form a mass (36) containing entrapped gas and entrapped molten aluminium metal and having a bulk or apparent density less than aluminium. The mass is allowed to accumulate as a mass of solid aluminium carbide containing product on the upper surface of the bath. The carbonaceous material is a hydrocarbon material or is produced by pyrolysis, decomposition or cracking of a hydrocarbon material.