Novel waterglass compositions comprise a zirconium containing anionic aggregate, preferably potassium zirconium carbonate or ammonium zirconium carbonate, in a quantity sufficient to provide at least 0.5% as zirconium metal. The compositions can be dried and/or gelled to form optically clear interlayers useful in the production of fire resistant glass laminates. The incorporation of the zirconium containing aggregate improves the fire resistant performance of the laminates.