boric oxide

Boric Oxide

Increase yield and strength in glass and ceramics

This pure anhydrous form is ideal where boric acid is required without metals. A powerful tool in the production of specialty glasses, ceramics, enamels, and welding/soldering fluxes.
Boron oxide in ceramics

The Benefits of Boron Are Crystal Clear

20 Mule Team® Borax boric oxide, the pure form of B2O3, is ideal for scenarios that require B2O3 without the presence of metals, or when water would be detrimental. This hard, glassy, granular product is water soluble, but at a much slower rate than boric acid—and reacts exothermically when wetted. When exposed to the atmosphere, it slowly absorbs water, reverting to boric acid.


Glass formulations

Boric oxide helps to reduce melting temperatures, increase thermal resistance and mechanical strength, and enhance aqueous and chemical durability. Pure B2O3 is necessary for the production of certain types of glass:
  • Optical lenses
  • Telescope lenses
  • Medical glass (ampoules)
  • Electronic glass
  • Glass-ceramic composites


Boric oxide is used by ceramic manufacturers used to produce elemental boron as well as various types of high-strength and heat-resistant ceramic products:
  • Boron carbide
  • Boron nitride
  • Titanium diboride
  • Zirconium diboride
Boric oxide is used in the manufacture of ceramics for many reasons, including its ability to increase the yields, strength, and scratch and chemical resistance of ceramic wares:
  • Wall and floor tiles
  • Tableware
  • Porcelain
  • Enameled appliances

Final glazes and enamels also benefit from boron’s influence on both the melting and physical properties of the product.


Boric oxide is an excellent solvent for metallic oxides at high temperatures. It is useful in the preparation of special welding and soldering fluxes, the hardening of steel, and the production of alloys with iron, nickel, or manganese. Boric oxide is also used to produce amorphous metal and rare-earth magnets.


Chemically bonded firebricks and castables require resistance to high temperature, abrasion, and corrosion. Boric oxide is used as a binder for magnesia-based refractory bricks and as a stabilizer for dolomite refractory bricks, commonly used in steel-smelting furnaces.

And, more

Finally, boric oxide is used as a catalyst in the conversion and synthesis of many organic compounds, as well as in the preparation of boron halides, sodium borohydride, metallic borates, and borate esters.

More than half of global borate usage is devoted to vitreous applications, including fiberglass, textile fiberglass, borosilicate glass, ceramic frits and glazes, and porcelain enamels for steel and aluminum.


Boric Oxide APPLICATIOns
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When added to enamel mixtures, boric oxide helps to prevent cracking and promotes a smooth surface and high luster.


Available Grades

The normal glassy form of boric oxide has no definite melting point. It begins to soften at about 325°C (617°F) and subsequently flows above 450°C (842°F).

Boric oxide is a hygroscopic product. Avoid exposure to water or humidity, which can cause caking. If wetted, the project reacts exothermically, forming boric acid, so maintaining the integrity of the packaging is also essential.

Approximately 56.3 kg of boric oxide are the chemical equivalent of 100 kg of boric acid.

The reaction of boric oxide with water is highly exothermic.


Chemical and Physical Properties

Molecular weight: 69.62

Specific gravity: 1.84

Appearance: Hard, glassy granules

Melting point: 450°C to 465°C (842°F to 869°F)

Stability: Hygroscopic; avoid exposure to water or humidity and maintain packaging integrity to prevent caking and the formation of boric acid.

Chemical Composition (Theoretical)

Boric oxide, B2O3: 100% 

Containers: Products may be available in bulk, IBCs, or small bags

Boric Oxide in Action 

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U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 500 customers with more than 1,700 delivery locations globally. We supply 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles.  Learn more about Rio Tinto.

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