Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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castor oil

A colorless to pale yellow or greenish, viscous, non-drying fatty oil of high viscosity, extracted from beans of the castor oil plant (Ricinus communis). It consists almost entirely of the glyceryl esters of ricinoleic acid. At low temperatures it thickens; it solidifies at approximately -10 to -18° C. It is used in leather finishing processes, and, in the sulfated form, as a preservative for leather bindings. Sulfating the oil, by reacting it with sulfuric acid. allows it to react with water. This is beneficial for books stored under hot, dry conditions, as it helps keep the leather soft and pliable under conditions of low relative humidity. (173 )




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