Utilizing sol-gel processing and supercritical CO₂ drying, low-price transparent aerogel was synthesized from waterglass. By adding water the feed waterglass was diluted and subsequently the aqueous waterglass sol liquor was obtained by mixing and adding hydrochloric acid or sulfuric acid as a catalyst and alcohol as a diluent. The wet waterglass gel was then obtained by gelating the sol liquor in an oven at 313.15K. Purified wet gel was obtained by removing the residual salts in the open pores of the wet gel by water and by substituting the water in the pores by alcohol. The wet gel is in general extremely porous and fragile. Thus, to prevent the destruction of the pores, supercritical CO₂ drying was employed to obtain dried aerogel. The hydrophilic nature of the dried aerogel was stabilized as hydrophobic by the surface methoxy with methanol to prevent destruction of the pores of the gel by moisture in the air. The effects of different type of acids and diluent on the gelation time and on the physical properties of the dried aerogel were quantitatively evaluated by the measurement of density and such analysis as FTIR, TGA, and UV transmitivity. The lowest density obtained in the present work was 0.057g/cm³ and accordingly we found that the waterglass aerogel can be a cheap but valuable new material for transparent thermal insulation.