The present invention provides a composition comprising an acidified aqueous solution of (1) micro colloidal silicic acid, (2) boric acid, and (3) a water absorbing additive, having a pH value of equal to or less than 1, wherein the micro colloidal silicic acid has particle sizes in the range of 1-8 nm, especially in the range of 1.5-6 nm. The invention also provides a particulate product obtainable by the method according to claim 18, wherein the particles comprise (1) silicic acid, (2) boric acid, and (3) the water absorbing additive, and wherein at least 90% of the particles in the particulate product have particle sizes in the range of 0.3-5 µm.
