The most efficient method to investigate nucleation phenomena is to measure the undercooling temperature at the beginning of the solidification process since it gives information about whether or not a certain substrate favors the heterogeneous nucleation. In this work a suitable experimental setup has been designed and developed for the study of nucleation phenomena, where a silicon droplet is directly placed and melted on a substrate. The melting-solidification process was filmed and the undercooling temperature was simultaneously measured by monochromatic and bichromatic pyrometers. For all the studied substrates the melting process started from the bottom of the sample where there was a contact with the substrate. In the case of zyarock and fused silica substrates, on which we focalize in the present paper, the temperature profile of the silicon sample presented a temperature plateau during melting and a typical cooling curve showing undercooling, recalescence and a plateau denoting that solidification occurred under isothermal conditions. It was also found that the nature of the substrates influences the measured undercooling values and the shape of the solidified silicon droplets.