agar

Scope note: Gelatinous polysaccharide substance extracted from various species of Rhodophyceae red seaweed, that grow in the Pacific and Indian Oceans and the Japan Sea. Agar contains agarose and agaropectin. 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. 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, as an emulsifying agent in foodstuffs, photographs, dental mold materials, cosmetics, and adhesives, to make an experimental synthetic gauzelike fabric in England. Agar is available in dried cakes, coarse granules, long strips, and thin sheets. The primary commercial sources for agar are Japan, New Zealand, Australia, Russia, and the United States. According to legend, agar was first discovered in the mid-17th century in Japan.

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