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.