Abstract: Water glass composition comprising a water-soluble or water-dispersible silicate binder and an inorganic phosphate curing agent, wherein said inorganic phosphate curing agent is composed of an inorganic solid fine powder comprising as the main ingredient a silicon polyphosphate or its metal salt and said curing agent has an initial dissolution amount (B) of up to 200 mg and an average hydrolysis rate constant (A) of at least 0.2, said initial dissolution amount (B) and average hydrolysis rate constant (A) being defined by the following formula:Y = AX + Bwherein X stands for the lapse of time (minutes) of up to 120 minutes after 1 g of the curing agent has been added to 100 ml of a 4N sodium hydroxide aqueous solution, and Y stands for the integrated amount (mg/100 ml) of phosphoric acid dissolved out of the curing agent into said aqueous solution during the time X.