Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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agar ( agar-agar )

The polysaccharides agarose and agropectin, occurring as cell-wall constituents of red marine algae (genera Gelidium, Gracilaria, etc.), from which it is extracted by hot water. It is available as a dry powder, flakes, or strips. Agar is the metallic (usually calcium) salt of a sulfuric acid ester of a complex polysaccharide of gelactose, but its exact structure is not understood. It dissolves in hot water and, upon cooling, sets to a jelly at concentrations as low as 0.5%. It is used as a gelling and stabilizing agent, as a misciformis sizing for silk, and as an adhesive emulsifying agent. (72 )




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