Jump to navigation Jump to search


A gelatin-like, polysaccharide substance extracted from various species of red Seaweed, belonging to the Rhodophyceae class, that grow in the Pacific and Indian Oceans and the Japan Sea. According to legend, agar was first discovered in the mid-17th century in Japan. Agar contains agarose and agaropectin. Agar is available in dried cakes, coarse granules, long strips and thin sheets. It is strongly hydrophilic and can absorb over 20 times its own weight in cold water. Agar dissolves in hot water and forms a stiff, clear jelly upon cooling, even at concentrations as low as 0.7%. However, when agar films are desiccated, they shrink significantly. Most commonly used as a media for culturing bacteria and fungi, agar has also been used for sizing textiles and paper. It is an important emulsifying agent in foodstuffs, photographs, dental mold materials, cosmetics, and adhesives. Agar was also used to make an experimental synthetic gauzelike fabric in England. The primary commercial sources for agar are Japan, New Zealand, Australia, Russia, and the United States.


Agar-Agar, Gettens 100.B48.TIF

Synonyms and Related Terms

agar-agar (AAT); agar (Esp., Port.); agar agar (It.); agar-agar (Fr.); agar agar; agal-agal; Chinese isinglass; Chinese gelating; Japanese gelatin; Japanese isinglass; kantan; Australian agar; gelose; Bengal isinglass; Bengal gelatin; Ceylon isinglass; Ceylon gelatin; agarose


  • Nonflammable.
  • No known hazards.
  • ThermoFisher: SDS

Physical and Chemical Properties

  • Insoluble in ethanol; swells in cold water.
  • Slowly soluble in hot water and forms a gel on cooling (37-40 C)
  • CAS = 9002-18-0
  • Melting Point = 60-97 (gel)

Resources and Citations

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p.19
  • Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
  • Fairchild's Dictionary of Textiles, Phyllis G.Tortora, Robert S. Merkel (eds.), Fairchild Publications, New York City, 7th edition, 1996
  • S.R.Trotman, E.R. Trotman, Textile Analysis, J.B. Lippincott Company, Philadelphia, 1932
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997