Sand cores in sand casting and permanent molds are manufactured by combining sand and binders. In this process, high-temperature molten metals decompose binders into gases, causing pore defects during casting since the gases cannot escape completely. Therefore, eco-friendly inorganic binders with reduced pore defects have gained attention. A quantitative analysis of inorganic binder gas generation was conducted in this study using a thermogravimetry-mass spectrometry (TG–MS) coupling system, wherein the specimens solidified a liquid inorganic binder only instead of a mold block mixed of sand and binder. At 1000 °C, the inorganic binder lost approximately 33.2% weight while releasing water vapor and CO₂. The decomposition temperature was between 150 and 300 °C for water vapor, and between 450 and 550 °C for CO₂. In the Ar gas atmosphere, the weight of gaseous emissions was the same as the TG weight loss; however, in the air, the weight of gaseous emissions was approximately 10% higher than the TG weight loss. Using these results, gas defects in a product can be predicted by calculating the used weight of binder during molding and tracking gases diffusion during casting.