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Refractory investment for casting

· 1 min read · Materials

Investment is a refractory plaster with silica that surrounds the wax model and withstands the heat of molten metal; it is mixed with water, vacuumed and burned out.

Illustration: Refractory investment for casting

Investment is a refractory plaster powder with silica. Mixed with water it forms a paste poured over the wax tree inside a flask. Once set and burned out it leaves a hollow mold in the shape of the piece.

Properties #

  • Composition: plaster with silica (quartz, cristobalite)
  • Mix: powder and water in the maker's proportions.
  • De-gassing: in a vacuum chamber to remove bubbles.
  • Burnout: in a programmed kiln at about 700 °C.
  • Types: for gold, silver and platinum, with different temperatures.

Uses in jewelry #

Pros and cons #

Advantages #

  • Reproduces very fine detail.
  • Withstands thermal shock.
  • It is the basis of lost wax.

Limitations #

  • Used only once.
  • Silica dust is hazardous.
  • A badly made mix gives rough surfaces.

Care and cleaning #

  • Measure powder and water precisely.
  • Wear a mask with a silica filter.
  • Keep the powder dry and tightly closed.

See also #

This entry was drafted with the help of AI and is pending review by the author.