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An old brand name for a hard, dark, shiny rubber developed in the 1830's. First produced by Thomas Hancock in England, the term 'Ebonite' was used for marketing in Great Britain while the name Vulcanite was used in the U.S. Ebonite is made by heating natural rubber with 10-32% sulfur. This is a much higher sulfur concentration than is usually used in vulcanization and the process results in an extremely brittle, dense moldable product. Ebonite was given its name because it resembled the hardwood ebony. Early uses for Ebonite included piano keys, fishing reels, clarinet mouthpieces, and electrical insulation. Vulcanized rubber may gradually decompose in heat or light emitting sulfur rich fumes that may attack metals.

Synonyms and Related Terms

vulcanite; ebonita (Esp.); ebonite (Port.)

Other Properties

Spot test for vulcanized rubber: Iodine/sodium azide reagent for presence of reducible sulfur compounds - positive reaction generates bubbles (Daniels and Ward, 1982)

Density 1.15
Refractive Index 1.66

Hazards and Safety


Emits hydrogen sulfide and other sulfur containing gases upon degradation

Additional Information

V.Daniels, S.Ward, "A Rapid Test for the Detection of Substances which will Tarnish Silver" Studies in Conservation 27:58-60, 1982.

Sources Checked for Data in Record

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 676
  • Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
  • Pam Hatchfield, Pollutants in the Museum Environment, Archetype Press, London, 2002
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • Website address 1 Comment: www.me.umist.ac.uk/historyp/ebonite.htm
  • Website address 2 Comment: www.nswpmith.com.au/historyofplastics.html
  • CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: density=1.1; ref. index=1.66 (red)