In a process to make hollow micro-spheres from boron silicate using a solution of Na 2O, SiO 2and B 2O 3, boric acid is mixed with caustic soda to form a solution. This solution is mixed in a pre-determined ratio with sodium silicate solution. The resulting solution is injected via a jet into a spray tower, resulting in the formation of hollow micro-spheres. The ratio of Na 2O, SiO 2and B 2O 3is in the range 1:10; 0.44:1;2.49:0.44, preferably 1:2.1:0.44. The ratio of boric acid to caustic soda is 35.7 Ma-% to H 3BO 3powder to 64.3 Ma-% in 33.33% caustic soda.
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