An apparatus has been constructed wherein the transparency of a glass/polymer sheet/glass assembly undergoing vacuum de-airing can be monitored continuously. Experimental conditions can be varied independently, such as vacuum level, cold (ambient) de-airing time, and oven temperature. The behavior of polyvinyl butyral and an ionomeric interlayer (SGP) with different rheological properties and surface roughness were studied using various de-airing conditions. initial results show that the clarity of the assembly is a monotonically increasing function of time in the oven at a given vacuum level. All assemblies made from these interlayers became clear with sufficient vacuum time at ambient temperature. The assembly from polyvinyl butyral with protrusion-type surface pattern clears up faster than that with indentation-type.