The drying characteristics of sodium silicate film containing as additives zinc oxide, zinc carbonate, kaolin and potassium phosphate has been observed by thermogravimetric analysis. The zinc compound additives react slowly with sodium silicate to insolubilize the latter, whereas kaolin reacts relatively rapidly by heat treatment at 110 ℃. Sample containing potassium phosphate contains residual moisture even after the heat treatment for 3 hours. The informations from this study about the drying and reaction characteristics of sodium silicate containing additives may be used for obtaining a crackfree inorganic film made insoluble in water by treatment at relatively low temperatures.