A method of filling cracks in existing fire resistant material located within door and window glazing frames, or of filling cavities within building elements such as door or window frames, dry wall constructions, floors, panels or filler bars, to produce a building element or a semi-finished product at least partially filled with a fire resistant material comprising the steps of: i) at the point of use, mixing together at least two precursor components prepared and retained separately in at least one transportable container, to form a precursor product; ii) applying the precursor product to the cracks or cavities in the existing fire resistant material in the glazing frames or to the cavities within the building element; and iii) allowing the precursor product to harden to form a fire resistant material, wherein one of the at least two precursor components comprises at least one waterglass; and a second of the at least two precursor components comprises a waterglass hardener; and wherein at least one of the two precursor components comprises a cooling agent and/or an insulating agent; and wherein the waterglass and waterglass hardener are kept separate prior to the point of use; and wherein the waterglass is present in the precursor product in a concentration range of from 2 to 90 wt %; and wherein the waterglass hardener is present in the second precursor component in a concentration range of 0.5 to 50 wt %; and wherein once hardened the fire resistant material forms a water-form stable and water stable fire resistant material which does not change shape by more than 20 % following contact with water. i) at the point of use, mixing together at least two precursor components prepared and retained separately in at least one transportable container, to form a precursor product; ii) applying the precursor product to the cracks or cavities in the existing fire resistant material in the glazing frames or to the cavities within the building element; and iii) allowing the precursor product to harden to form a fire resistant material, wherein one of the at least two precursor components comprises at least one waterglass; and a second of the at least two precursor components comprises a waterglass hardener; and wherein at least one of the two precursor components comprises a cooling agent and/or an insulating agent; and wherein the waterglass and waterglass hardener are kept separate prior to the point of use; and wherein the waterglass is present in the precursor product in a concentration range of from 2 to 90 wt %; and wherein the waterglass hardener is present in the second precursor component in a concentration range of 0.5 to 50 wt %; and wherein once hardened the fire resistant material forms a water-form stable and water stable fire resistant material which does not change shape by more than 20 % following contact with water. one of the at least two precursor components comprises at least one waterglass; and a second of the at least two precursor components comprises a waterglass hardener; and wherein at least one of the two precursor components comprises a cooling agent and/or an insulating agent; and wherein the waterglass and waterglass hardener are kept separate prior to the point of use; and wherein the waterglass is present in the precursor product in a concentration range of from 2 to 90 wt %; and wherein the waterglass hardener is present in the second precursor component in a concentration range of 0.5 to 50 wt %; and wherein once hardened the fire resistant material forms a water-form stable and water stable fire resistant material which does not change shape by more than 20 % following contact with water. the waterglass is present in the precursor product in a concentration range of from 2 to 90 wt %; and wherein the waterglass hardener is present in the second precursor component in a concentration range of 0.5 to 50 wt %; and wherein once hardened the fire resistant material forms a water-form stable and water stable fire resistant material which does not change shape by more than 20 % following contact with water.