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Description: Zirconium Silicate Glaze Opacifier

Oxide Analysis Formula
ZrO2 65.00% 1.00
SiO2 35.00% 1.10
Oxide Weight 189.57
Formula Weight 189.57


Ultrox is a brand name for zircon.
Three types are available: Ultrox, Ultrox 500W, Ultrox 1000W.
This superfine particle sized material is a testament to the efficiency of modern grinding equipment.

Ultrox opacifiers are claimed to assure uniformity of glaze opacity, texture and color over a wide range of temperatures and compositions. They reduce the expansion of glazes and tend to reduce crazing. They increase the resistance of glazes to chemical attack and widen the firing range. Ultrox melts at 4000F and has a coefficient of thermal expansion of 42 x 10-7, a hardness of 7.5 Moh and index of refraction of 2. It is composed of 65% ZrO2 and 35% SiO2 in a formula of ZrO2:SiO2.

Ultrox is used for the production of both white and color glazes for sanitary ware, wall tile, glazed brick, structural tile, stoneware, dinnerware and special porcelains. It is used in amount of 12-20% of the glaze batch.

-Ultrox has an average particle size of 2 microns.
-Ultrox 500W has an average particle size of 1 micron and thus provides greater whitening power. It lightens color appreciably and thus requires more stain.
-Ultrox 1000W has an average particle size of .5 micron and provides the maximum reflectance and opacity.

Ultrox has an extremely high melting point and low uniform thermal expansion and can thus be slip cast or pressed to produce zirconium silicate refractories (for use in glass melting furnaces, foundries, refractory porcelains, washes for refractory slabs, refractory cements). Compositions of Ultrox alone can approach the theoretical density of zircon.

Coefficient of thermal expansion: 42 x 10 -7
Hardness: 7.5 Moh's scale
Index of refraction: 2

Ultrox products are relatively non-hazardous based on plant operating experience. Avoid inhalation of dust. May cause eye irritation on repeated contact.

Ultrox is zirconium silicate, thus the same as Zircopax Plus or Superpax. Although a finer particle size.

Related Information

Ultrox Original Container Bag

These bags actually contain Zircopax Plus since Trebol is the new owner of the company.

Ultrox 500W original container bags


Materials Zircon
Materials Opax
Materials Superpax
Materials Zircopax Plus
Typecodes Opacifier
Opacifiers are powders that turn transparent glazes opaque by various chemical and physical mechanisms (and combinations of mechanisms).


Frit Softening Point 2200C
By Tony Hansen
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