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Hollow Glass Microsphere
ITM11462, ITM11519, ITM11661, ITM11667, ITM11689, ITM11722, ITM11724, ITM18397, ITM19804

3M™ Glass Bubbles K20 glass bubbles have a density of 0.20 g/cc and an isostatic crush strength of 500 psi.


  • Decreases density and increases buoyancy to help improve efficiency and may lower material costs
  • Provides excellent water and oil resistance for use in underwater applications
  • Stable voids for low thermal conductivity and reduced dielectric constant
  • Versatile use – adaptable to a variety of production processes
  • Low density, chemically stable bubbles are ideal additives for emulsion explosives

What are 3M™ Glass Bubbles? 

The general purpose K Series glass bubbles are the most versatile and economical 3M™ Glass Bubbles. Our 3M™ Glass Bubbles K20 are engineered hollow glass spheres made from water-resistant and chemically-stable soda-lime borosilicate glass. Like all 3M glass bubbles, our K20 glass bubbles are water and oil resistant, providing better utility in underwater applications. Additionally, they are non-combustible and non-porous, so they do not absorb resin; and their low alkalinity makes this product compatible with most resins while providing a stable viscosity and a long shelf life. 

3M glass bubbles are a superior alternative to many conventional fillers and additives such as silicas, calcium carbonate, talc, clay and other materials used in demanding applications. Our low-density spheres are used in a wide range of industries to reduce part weight, may lower costs and enhance product properties — making them more reliable and affordable than many alternatives such as cenospheres and perlite. 

Strength-to-Weight Ratio 

The benefits don't end there; although these hollow spheres have thin walls, they have an isostatic crush strength of 500 psi, making them suitable for a number of buoyancy applications, including additives in buoys and shallow water buoyancy applications (e.g. up to 2,000 feet of sea water). K20 bubbles have a fractional survival rate of 80% or more, at 500 psi for consistent performance in highly filled resin systems. 

The unique spherical shape of these bubbles offers a number of additional benefits, including: higher filler loading, lower viscosity/improved flow and reduced shrinkage and warpage. Higher filler loading offers the potential for lower costs. Adding to this product's versatility is its ability to be easily blended into compounds — making it adaptable to a variety of production processes including spraying, casting and molding. 

Buoyancy Benefits and Applications 

The ideal combination of high strength and low density has made 3M glass bubbles an industry-standard additive for syntactic foams used in buoyancy modules, buoys or buoyancy blocks for undersea vehicles. When 3M glass bubbles are formulated with resin, the resulting syntactic foam has a high strength-to-density ratio to provide maximum net buoyancy for a given depth rating. The bubbles also produce stable voids, which results in low thermal conductivity and low dielectric constant. 

Emulsion Explosives 

3M glass bubbles K20 (PDF, 82.47 Kb) can be used in many applications. One common use is as a sensitizer for emulsion explosions. Emulsion explosives are mixtures of saturated inorganic oxidizers like ammonium nitrate saturated in water, and mixed with fuel. To get mixtures to detonate reliably, with the right sensitivity, you need to add a sensitizer. Our glass bubbles are commonly used as a sensitizer in these applications because they are reliable, low density, chemically stable objects. 

Typical Applications

  • Bowling balls
  • Paints and coatings
  • Cast polyester
  • Caulk
  • Explosives
  • Polyester putty
  • Sealants
  • Adhesives
  • Potting compounds
  • Tooling boards
  • Spackling compound