Boron Oxide B2O3

  • Glass-former and flux but has similar molecular structure to alumina
  • Major exception to neat structure of Seger UMF
  • Has melting point of 1992°F but starts melting at 572°F
  • excellent low-temp flux
  • Cone 10 glazes containing it start to melt very early but it also volatilizes over 2102°F
  • Produces good color response in glazes
  • Characteristics include Bluish, milky streaks and cloudy effect
  • Copper red glazes and brightly colored glazes, from 5-15%, at cone 10
  • Low expansion and contraction rate
  • aids in reducing crazing
  • if more than 10% in glaze loses elasticity and ant-crazing effect may be reversed
  • Low viscosity and surface tension
  • glazes containing boron will be smooth and glossy
  • may even run onto the shelf it applied too heavily
  • Element has no known toxicity but is soluble
  • Soluble sources include Gerstley Borate (and subs), colemanite, ulexite, borax, and boric acid
  • Insoluble sources are Frits, which are slightly soluble.

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