The microstructure of BaTiO3 ceramics and their mechanical and electrical properties normally develop as a result of liquid-phase sintering. BaTiO3 is usually sintered with a small excess of titania of 1-4 mol%. This excess reacts with BaTiO3 to create the eutectic melt BaTiO3-Ba6Ti17O40. In addition, numerous sintering additives have been used to obtain a homogeneous microstructure and to improve the properties of the final ceramics. Obviously, such additives will also form new liquid phases or at least modify the composition of the above-mentioned eutectic. Generally, information about the possible liquid phases has to be taken from the equilibrium diagram of the relevant multi-component system. However, only a few phase diagrams of such systems have been completely determined. Moreover, the liquid-phase-forming process occurs only in microregions inside the sintering body, whose local composition is normally unknown. The primary aim of this work was to develop a method that allows the effects of additives on liquid-phase formation in BaTiO3 ceramics to be estimated. For this purpose arrangements of powder-tips with the composition of the appropriate additive and substrates of BaTiO3 were examined in a heating microscope. In this way, the microregions inside the sintering body, where the additive is in contact with BaTiO3, can be simulated by the contact plane between the powder-tip and the BaTiO3 compact. Using the abilities of modern video equipment the heights of the powder tips were measured and analysed. The corresponding plots of height versus heating time or temperature give information about the progress of the melting process. The results for additives of CuO, SiO2 and Ba2TiSi2O8 are presented. Moreover, a theory concerning the final stage of the anomalous grain growth during liquid-phase sintering could be derived from experiments with green bodies as substrates.