storax, any of about 120 species of the genus Styrax, shrubs and trees of the family Styracaceae, mostly in tropical or warm regions. The deciduous leaves are alternate and short-stalked. The white flowers, usually borne in pendulous terminal clusters, have a five-lobed corolla (the petals, collectively). Among the best-known cultivated species are S. japonicum (Japanese snowbell), native to East Asia and growing to about 9 metres (30 feet) tall; S. obassia (fragrant snowbell), native to Japan and growing to about 9 metres; S. americana, native to southeastern North America and growing from 1.8 to 2.7 metres (6 to 9 feet); and S. officinalis (snowdrop bush), native to eastern Europe and Asia Minor and growing to about 6 metres (20 feet). A resin known as storax, used in incense, was formerly obtained from S. officinalis.

This article was most recently revised and updated by Amy Tikkanen.
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resin, any natural or synthetic organic compound consisting of a noncrystalline or viscous liquid substance. Natural resins are typically fusible and flammable organic substances that are transparent or translucent and are yellowish to brown in colour. They are formed in plant secretions and are soluble in various organic liquids but not in water. Synthetic resins comprise a large class of synthetic products that have some of the physical properties of natural resins but are different chemically. Synthetic resins are not clearly differentiated from plastics.

Most natural resins are exuded from trees, especially pines and firs. Resin formation occurs as a result of injury to the bark from wind, fire, lightning, or other cause. The fluid secretion ordinarily loses some of its more volatile components by evaporation, leaving a soft residue at first readily soluble but becoming insoluble as it ages. The ancient Chinese, Japanese, Egyptians, and others used resins in preparation of lacquers and varnishes.

Natural resins may be classified as spirit-soluble and oil-soluble. Among the former are balsams, long popular as a healing agent; turpentines used as solvents; and mastics, dragon’s blood, dammar, sandarac, and the lacs, all used as components of varnishes. The oil-soluble resins include rosin, derived along with turpentine from the long-leaf pine and long used for a variety of applications, including soapmaking; copals, used in varnishes; amber, the hardest natural resin, fabricated into jewelry; Oriental lacquer, derived from a tree native to China; and cashew-nutshell oil, derived from cashew nuts.

In modern industry natural resins have been almost entirely replaced by synthetic resins, which are divided into two classes, thermoplastic resins, which remain plastic after heat treatment, and thermosetting resins, which become insoluble and infusible on heating.

This article was most recently revised and updated by Amy Tikkanen.
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