3M™ Glass Bubbles HGS4K28 are hollow microspheres made of soda-lime borosilicate glass with a true density of 0.28 g/cm³ and an isostatic crush strength of 4,000 psi / 280 bar.
These Glass Bubbles are designed for buoyancy and insulation in deep water applications. S series Glass Bubbles generally offer smaller particle sizes than the K series. 3M™ Glass Bubbles S32 are ideal additives for shallow water buoyancy applications and applications in thermoset resins like polyurethane and epoxy polymers. They are virtually insoluble in water or oil.