The mechanism of the first stage of reverberatory tin smelting, in which tin concentrates are reduced with solid carbon, has been studied by conducting kinetic experiments in a thermobalance and in small-scale crucible melts. The aims were to explore the factors that favor the early removal of tin metal from the furnace and to minimize the transfer of iron into tin at this stage. SnO vapor has been shown to be an intermediate phase in the reduction of SnO*l2*s by carbon. Temperature changes in the range 800-1000°C are unlikely to change the relative rates of reduction of tin and iron, but the rate of dissolution of iron in tin is slow. Thus, the more rapid the reduction, the less chance the iron has to dissolve in the tin. The form of the carbon reductant and the iron content of its ash will affect the level of iron transfer to the liquid tin. Limestone in the charge can be a potential cause of tin being locked up in the solid charge because SnO vapor combines with CaO to form calcium stannate. The Laboratory results were compared with data from a Malaysian smelter.