Enamelled Fireclay

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Fireclay

Fireclay is type of sedimentary or residual clay. Some siliceous clay rich in hydrous aluminium silicates, capable of withstanding high temperatures without deforming, disintegrating, or becoming soft and pasty.

Colour is due to contamination of iron oxide, free from fluxes such as iron, alkaline earths, alkali and excess silica.

Highly refractory, fire clay does not fuse below 1600 °C. Fire clay is rich silica, but contains only small amounts of lime, iron, and alkali. It approaches kaolin in composition, the better grades containing at least 35% alumina when fired.

Composition

  • 50.90% SiO2
  • 34.73% Al2O3
  • 0.33% K2O
  • 0.33% Na2O
  • 0.28% MgO
  • 0.28% CaO
  • 1.34% Fe2O3
  • 1.81% TiO2
  • 9.99% L.O.I

Specific Gravity: 2.6

Melting Point: 3000 °F

Enamel

A vitreous substance made of finely powdered glass colored with metallic oxide and suspended in an oily medium for ease of application with a brush. The medium burns away during firing in a low-temperature muffle kiln (about 965°-1300° F or 500°-700° C). Sometimes, several rings are required to fuse the different colors of an elaborately enameled object.