To assess the effect of metallic particles (MPs) on heat transfer in glassy mold flux, a structurally stable glassy mold flux system composed of CaO-Al2O3-CaF(2)was examined with 0, 2, or 5 wt% of FeO or Fe MPs. The change of extinction coefficient by Mie Scattering of the Fe particles and absorption by FeO was quantified using Fourier transformation infrared ray spectroscopy and an Ultraviolet/Visible spectrometry. Thermal conductivity of mold flux film with dispersed MPs was quantified using laser flash technique. One-dimensional Debye temperature was calculated, and particle morphology and size distribution were observed using image analysis to explain variations in thermal conductivity among the glass samples. Finally, to simulate the heat transfer ratio by both the conduction and radiation, the actual heat flux through mold flux film was measured using an Infrared Emitter Technique. The overall heat transfer rate across liquid flux film could be reduced significantly by a dispersion of MPs.