In this paper, the formation of mineral wool fibres has been studied on a real industrial production process. Parametric dependence of the melt film structural dynamics on the spinner wheel rotational frequency was investigated. The results presented indicate the presence of the melt instability that is formed as a complex quasi-periodic oscillation of the structures on the melt film surface. In addition to the melt oscillations which coincide with the rotating frequency of the spinner wheel and its higher harmonics, aperiodic melt structures also appear These structures result from the Taylor instability, which is inherent to liquid movement and is one of the basic mechanisms of the formation of melt ligaments that solidify into mineral wool fibres. Based on the results, a phenomenological model for structural instability as a function of the wheel rotational frequency was formed, indicating a characteristic influence of melt film dynamics on the fibre formation and indirectly, on the quality of the end Product. (C) 2013 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers.