The penetration of gas bubbles through liquid–liquid interfacesInterface plays a critical role in metallurgical processesProcess, particularly in copper smeltingCopper smelting, where the copper matte loss in the slag depends on bubble-induced entrainment dynamics. This study quantifies the light phase entrainment volume and even film thickness on the rising bubbles with bubble size and fluid propertiesProperties, i.e. densityDensity, viscosityViscosity, and interfacial tension. Experiments reveal that entrainment volume of heavier liquid transported by rising bubbles decreases with increasing both upper and lower liquid phase viscosityViscosity, heavy liquid densityDensity, and interfacial tension. Besides, it was also observed three typical entrainment regimes correspond to different entrainment volume with increasing bubble diameters from 3.16 to 7.17 mm. In copper smeltingCopper smelting, optimizing bubble size and slag viscosityViscosity (0.1–0.5 Pa·s) can minimize matte entrainmentMatte entrainment in slag, improving metal recovery. The findings provide actionable guidelines for process controlProcess control, emphasizing viscosityViscosity adjustment and bubble dispersion to enhance slag recovery.