Silicon Dioxide - Silica - SiO2

Unit 6 Topic 14
Oxide Qualities

Low temperature melt - lowest expansion - creates own glass network.


  • A glass-former - the most important oxide in all glazes and clays.
  • Increases will raise the melting range and increase the fluidity of the melt.
  • If amounts of silica are too low texture will be dry. High amounts produce a more refractory glaze with shiny surfaces.
  • Has a very low coefficient of expansion and in small amounts is a useful first measure in controlling crazing.
  • Additions may increase the hardness, strength and gloss of a glaze.
  • Occurs in 60% of the earth's crust - melts at 1710 deg.C
  • The only other substance giving similar results to silica is boric oxide but this also needs silica.


  • Flint, quartz and pure silica.
  • Feldspars, clays and other silicates - these all bring other oxides.
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