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Mineral: Feldspar

Notes

An indispensable material in the ceramic industry. Most ceramic bodies employ feldspar as a flux to vitrify them at a lower temperature (the feldspar creates a glaze that glues the more refractory particles together to form the fired matrix). Most medium and high temperature glazes employ it as a flux. Feldspars are naturally occurring crystalline rocks that will melt and cool to form a glass (nature cooled them slowly (devitrified) to for crystalline minerals. There are many kinds of feldspars, but in ceramics soda, potash and lime feldspars are the most common.

Porcelains can contain up to 50% feldspar, stoneware bodies around 15%. Feldspar sources K2O and Na2O to glazes, these can produce very brilliant results. However, the high KNaO produces a high thermal expansion which in turn produces crazing. Thus it is important to control the amount of feldspar and employ materials that source other low expansion oxides like CaO, MgO, Li2O, BaO, SrO, etc.

Out Bound Links

  • (Glossary) Feldspar Glazes

    Quite simply, feldspar glazes are high in feldspar. Feldspar by itself melts well at high temperatures, however to be a balanced glaze (durable, well fitted to the body, non-leachable, etc) it needs additions of other fluxes and silica. It is very educational to work through the process of comparing...

  • (Minerals - Related) K-Feldspar

    Most common feldspars contain both sodium and potassium. The term K-Feldspar designates one where the K2O/Na2O balance heavily favors K2O.

  • (Minerals - Related) Na-Feldspar

    Most common feldspars contain both sodium and potassium. The term Na-Feldspar designates one where the K2O/Na2O balance heavily favors Na2).

  • (Oxides) K2O - Potassium Oxide
  • (Oxides) Na2O - Sodium Oxide, Soda

By Tony Hansen




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