Hollow and solid glass microspheres and beads have been used in consumer and industrial products for decades.

My first purchases of glass spheres  was from Golden West Manufacturing during the mid-1980s.  In those days something called “Thomas Register” was the Google go-to for manufacturing research.  It was also where I looked for an inert material to use as an extender-filler in silicon mold making.  I later used glass beads when manufacturing luminous jewelry.   Goldenwest still sells glass beads:
During a 1994 studio visit with Dennis Oppenheim I suggested that he use glass beads as an additive to polyester castings for his Rabbit Factory series.

Clicking on the Goldenwest images above or those below will open links to purchasing glass beads.

“Properties of polymers are often modified by quasi-spherical mineral fillers such as calcium carbonate or by highly anisotropic glass fibres for an efficient reinforcement or by foaming to reduce their density. Solid or hollow glass beads partly combine the advantages and also the drawbacks of those techniques allowing to modify mechanical, optical and thermal properties, density and cost of nearly all the polymers. Their adhesion to the polymer matrix can be optimized by sizing with coupling agents. Moreover, glass beads have unique optical properties and can be modified by surface treatments to obtain electrical conductivity. Consequently their application field covers a broad domain comprising polymer enhancement or lightening with hollow glass beads having a low density, syntactic foams used for buoyancy, reflective products for signs and marking, electrical conductivity for metal coated glass beads used in electronics. Solid glass beads have a density of 2.5 g/cc, a high crush strength and a Moh hardness of approximately 6.” SpecialChem, 2006