A novel optical measuring method is described which was used for the density measurement of model samples of glass batch during the melting process. It used a sample volume of some 1000 mm(3) which was sufficiently large to suppress single particle effects. Shape changes of batch samples during heating were taken into account by the optical method. Volumetric changes of soda-lime-silica glass batch were monitored between room temperature and 1100 degreesC. Initially a sintering stage was observed showing self similar reduction in the sample volume. Thereafter, the sample shape approached the equilibrium surface of drops. This was accompanied by a large increase in volume, which was attributed to the formation of gas bubbles within the batch samples. A strong influence of heating rate and composition on this volume increase was observed.