Methods are described for recording and automated processing of the data obtained from phase-modulated speckle interferometry of optically dense (opaque to the intrinsic radiation) flames containing a condensed phase. The use of a high-speed single-frame measurement technique and special processing procedures makes it possible to determine the spatiotemporal distribution of the refractive index, based on which the flame structure can be identified. As an example, the results of investigation of the torch formed by burning a stationary medical paraffin droplet are presented.