Gypsum cement

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A group of cements that are produced from calcined Gypsum. Gypsum cement is also called gypsum concrete. In general, gypsum cements set slower and are more easily worked than Plaster of Paris. Many various formulations for gypsum cement are used. Initially, the gypsum is calcined at high temperatures to remove the bound water. The resultant Anhydrite (anhydrous calcium sulfate) is mixed with a salt solution (i.e., Alum, Borax, or Cream of tartar) then recalcined. Some contain Sand, Hair, or Straw as extenders and many may contain small amounts of salts (Potassium sulfate) as accelerants. Organic materials (Blood, Glue, Casein) and weak acids (Citric acid, Boric acid) can act as retardants.

Examples of gypsum cements include:

  • Keene's cement - anhydrite mixed with alum or aluminum sulfate.
  • Mack's cement - anhydrite mixed with sodium or potassium sulfate.
  • Martin's cement - anhydrite mixed with potassium carbonate.
  • Parian cement - anhydrite mixed with borax.
  • Scott's cement - anhydrite mixed with lime.
  • Spence's plaster - anhydrite mixed with Portland cement, sand, aluminum sulfate.

Synonyms and Related Terms

plâtre (Fr.); gesso (Port.); gypsum plaster; gypsum concrete; plaster of Paris; Keene's cement; Parian cement; Martin's cement; Mack's cement; Scott's cement; Spence's plaster

Resources and Citations

  • J.H.Wills, "Inorganic Adhesives and Cements" in Handbook of Adhesives, I.Skeist (ed.), Van Nostrand Reinhold, New York, 1977. p.117-138.
  • R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 286
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996