Physical interfaces that change appearance by controlling transparency have attracted attention for wide applicability. However, many existing methods are limited to planar objects, and it is difficult to control transparency in three-dimensional objects and to control transparency continuously. In this study, we propose a novel method to control the transparency of three-dimensional objects by utilizing the mechanical emulsification phenomenon of liquid. This approach is to fill the object with two transparent liquids that are liquid-liquid phase separated and agitate the liquids inside the object to make them cloudy and control their transparency. By using electrohydrodynamic (EHD) pumps, which can be freely positioned inside the object, to agitate the liquid, it is possible to control the transparency of complex three-dimensional objects. Continuous control is also achieved by changing the ratio of the two liquids. In this paper, we describe the details of proposed method for controlling the transparency and show application scenarios.