Metallic and non-metallic impurities as well as hydrogen and oxides may negatively affect the quality of an aluminium melt. By measuring the density index, it is possible to define, control and optimise the process of cleaning the melt, thereby improving the quality. In this way, the consistently high quality of the melt is assured and the reject rate efectively reduced. The MK 3000 is a stationary electronic balance for automatically calculating the density index of aluminium melt. The densities of the two samples (atmosphere sample and vacuum samples) previously cast using the Vacuum Density Tester, series 3VT or ALSP, are determined with the aid of the MK 3000 using the principle of Archimedes. The density index is then calculated automatically. This is an important indicator of the quality of the aluminium melt. The density index represents the percentage diference in density of the two samples. The lower the density index the cleaner the aluminium melt.