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A glassy material that floats to the top of molten metal during the smelting process. Slag is formed from the combination of Silica with flux materials such as Soda and Potash. It also incorporates other impurities that float to the surface, such as metal oxides. In ceramic kilns, slag is formed by the reaction of the fluxing materials with the refractory lining. Ancient iron and copper alloys often contain small pieces of slag that were incompletely separated from the metal. Slag is a useful residue that is incorporated in the manufacture of Concrete, Mineral wool, Slag brick, Slag glass, Portland cement, and Cinder block.

Synonyms and Related Terms

slage; dross; cinder; laitier (Fr.); Schlacke (Deut.); slak (Ned.); escória (Port.)

Physical and Chemical Properties

Density 2.0-3.9

Resources and Citations

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 728
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • David C. Scott, Metallography and Microstructure of Ancient and Historic Metals, The Getty Conservation Institute, Los Angeles, 1991
  • Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
  • Henry Hodges, Artifacts: An Introduction to Early Materials and Technology, Ronald P. Frye, Kingston, Canada, 1988
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: density=2.0-3.9