The kinetics of nucleation in a glass-forming melt having the composition (in mol %) 71.80 SiO2, 1.63 Al2O3, 23.20 Li2O, 2.20 K2O and 1.17 MoO3 is investigated. X-ray analysis, DTA, optical and electron microscopy are used together with precise viscometric data to follow the crystallization process and to characterize the properties of both the initial melt and the resulting crystalline phase — the rhombic Li2O · 2SiO2. By virtue of its composition, structure and properties the resulting semi-crystalline material is a model of typical glass-ceramic enamel. The analysis of the kinetic measurements demonstrated the non-steady state character of the investigated process of nucleation. Furthermore it is shown that the presence of small amounts of a surface tension lowering oxide (MoO3) in the melt considerably decreases the interface energy at the crystal/melt boundary. This explains the role of MoO3 and similar surface active oxides in inducing the bulk crystallization in glass-ceramic enamels.