A resin is a solid or highly viscous liquid that can be converted into a polymer. [1] Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, and predominantly terpenes. Well known resins include amber, hashish, frankincense, myrrh and the animal-derived resin, shellac. Resins are commonly used in varnishes, adhesives, food additives, incenses and perfumes.
Resins protect plants from insects and pathogens, and are secreted in response to injury. [2] Resins confound a wide range of herbivores, insects, and pathogens, while the volatile phenolic compounds may attract benefactors such as predators of insects that attack the plant. [3]
Most plant resins are composed of terpenes. Specific components are alpha-pinene, beta-pinene, delta-3 carene, and sabinene, the monocyclic terpenes limonene and terpinolene, and smaller amounts of the tricyclic sesquiterpenes, longifolene, caryophyllene, and delta-cadinene. Some resins also contain a high proportion of resin acids. Rosins on the other hand are less volatile and consist of diterpenes among other compounds.[ citation needed ]
Examples of plant resins include amber, Balm of Gilead, balsam, Canada balsam, copal from trees of Protium copal and Hymenaea courbaril , dammar gum from trees of the family Dipterocarpaceae, dragon's blood from the dragon trees ( Dracaena species), elemi, frankincense from Boswellia sacra , galbanum from Ferula gummosa , gum guaiacum from the lignum vitae trees of the genus Guaiacum , kauri gum from trees of Agathis australis , hashish (Cannabis resin) from Cannabis indica , labdanum from mediterranean species of Cistus , mastic (plant resin) from the mastic tree Pistacia lentiscus , myrrh from shrubs of Commiphora , sandarac resin from Tetraclinis articulata , the national tree of Malta, styrax (a Benzoin resin from various Styrax species) and spinifex resin from Australian grasses.
Amber is fossil resin (also called resinite) from coniferous and other tree species. Copal, kauri gum, dammar and other resins may also be found as subfossil deposits. Subfossil copal can be distinguished from genuine fossil amber because it becomes tacky when a drop of a solvent such as acetone or chloroform is placed on it. [4] African copal and the kauri gum of New Zealand are also procured in a semi-fossil condition.
Rosin is a solidified resin from which the volatile terpenes have been removed by distillation. Typical rosin is a transparent or translucent mass, with a vitreous fracture and a faintly yellow or brown colour, non-odorous or having only a slight turpentine odour and taste. Rosin is insoluble in water, mostly soluble in alcohol, essential oils, ether, and hot fatty oils. Rosin softens and melts when heated and burns with a bright but smoky flame.
Rosin consists of a complex mixture of different substances including organic acids named the resin acids. Related to the terpenes, resin acid is oxidized terpenes. Resin acids dissolve in alkalis to form resin soaps, from which the resin acids are regenerated upon treatment with acids. Examples of resin acids are abietic acid (sylvic acid), C20H30O2, plicatic acid contained in cedar, and pimaric acid, C20H30O2, a constituent of galipot resin. Abietic acid can also be extracted from rosin by means of hot alcohol.
Rosin is obtained from pines and some other plants, mostly conifers. [5] Plant resins are generally produced as stem secretions, but in some Central and South American species of Dalechampia and Clusia they are produced as pollination rewards, and used by some stingless bee species in nest construction. [6] [7] Propolis, consisting largely of resins collected from plants such as poplars and conifers, is used by honey bees to seal small gaps in their hives, while larger gaps are filled with beeswax. [8]
Shellac is an example of an insect-derived resin.
Asphaltite and Utah resin are petroleum bitumens.
Human use of plant resins has a very long history that was documented in ancient Greece by Theophrastus, in ancient Rome by Pliny the Elder, and especially in the resins known as frankincense and myrrh, prized in ancient Egypt. [9] These were highly prized substances, and required as incense in some religious rites.
The word resin comes from French resine, from Latin resina "resin", which either derives from or is a cognate of the Greek ῥητίνηrhētínē "resin of the pine", of unknown earlier origin, though probably non-Indo-European. [10] [11]
The word "resin" has been applied in the modern world to nearly any component of a liquid that will set into a hard lacquer or enamel-like finish. An example is nail polish. Certain "casting resins" and synthetic resins (such as epoxy resin) have also been given the name "resin".
Some naturally-derived resins, when soft, are known as 'oleoresins', and when containing benzoic acid or cinnamic acid they are called balsams. Oleoresins are naturally-occurring mixtures of an oil and a resin; they can be extracted from various plants. Other resinous products in their natural condition are a mix with gum or mucilaginous substances and known as gum resins. Several natural resins are used as ingredients in perfumes, e.g., balsams of Peru and tolu, elemi, styrax, and certain turpentines. [5]
Other liquid compounds found inside plants or exuded by plants, such as sap, latex, or mucilage, are sometimes confused with resin but are not the same. Saps, in particular, serve a nutritive function that resins do not.
Plant resins are valued for the production of varnishes, adhesives, and food glazing agents. They are also prized as raw materials for the synthesis of other organic compounds and provide constituents of incense and perfume. The oldest known use of plant resin comes from the late Middle Stone Age in Southern Africa where it was used as an adhesive for hafting stone tools. [12]
The hard transparent resins, such as the copals, dammars, mastic, and sandarac, are principally used for varnishes and adhesives, while the softer odoriferous oleo-resins (frankincense, elemi, turpentine, copaiba), and gum resins containing essential oils (ammoniacum, asafoetida, gamboge, myrrh, and scammony) are more used for therapeutic purposes, food and incense. The resin of the Aleppo Pine is used to flavour retsina, a Greek resinated wine. [13]
While animal resins are not as common as either plant or synthetic resins some animal resins like lac (obtained from Kerria lacca ) are used for applications like sealing wax in India, [14] and lacquerware in Sri Lanka.[ citation needed ]
Many materials are produced via the conversion of synthetic resins to solids. Important examples are bisphenol A diglycidyl ether, which is a resin converted to epoxy glue upon the addition of a hardener. Silicones are often prepared from silicone resins via room temperature vulcanization. Alkyd resins are used in paints and varnishes and harden or cure by exposure to oxygen in the air. [15]
Myrrh is a gum-resin extracted from a few small, thorny tree species of the Commiphora genus, belonging to the Burseraceae family. Myrrh resin has been used throughout history in medicine, perfumery, and incenses. Myrrh mixed with posca or wine was widely used in many ancient cultures to produce pleasurable feelings and as an anti-inflammatory and analgesic.
Varnish is a clear transparent hard protective coating or film. It is not to be confused with wood stain. It usually has a yellowish shade due to the manufacturing process and materials used, but it may also be pigmented as desired. It is sold commercially in various shades.
Frankincense, also known as olibanum, is an aromatic resin used in incense and perfumes, obtained from trees of the genus Boswellia in the family Burseraceae. The word is from Old French franc encens. There are several species of Boswellia that produce true frankincense: Boswellia sacra, B. frereana, B. serrata, and B. papyrifera. Resin from each is available in various grades, which depends on the time of harvesting. The resin is hand-sorted for quality.
Rosin, also known as colophony or Greek pitch, is a solid form of resin obtained from pine trees and other plants, mostly conifers, primarily through heating fresh liquid resin to vaporize the volatile liquid terpene components. Used widely in various industries and arts, rosin appears as a semi-transparent, brittle substance that ranges in color from yellow to black and melts at stove-top temperatures. Rosin consists mainly of resin acids, especially abietic acid, and is soluble in alcohol, ether, benzene and chloroform.
Balsam is the resinous exudate which forms on certain kinds of trees and shrubs. Balsam owes its name to the biblical Balm of Gilead.
Canada balsam, also called Canada turpentine or balsam of fir, is the oleoresin of the balsam fir tree of boreal North America. The resin, dissolved in essential oils, is a viscous, sticky, colourless or yellowish liquid that turns to a transparent yellowish mass when the essential oils have been allowed to evaporate.
Dammar, also called dammar gum, or damar gum, is a resin obtained from the tree family Dipterocarpaceae in India and Southeast Asia, principally those of the genera Shorea or Hopea. The resin of some species of Canarium may also called dammar. Most is produced by tapping trees; however, some is collected in fossilised form on the ground. The gum varies in colour from clear to pale yellow, while the fossilised form is grey-brown. Dammar gum is a triterpenoid resin, containing many triterpenes and their oxidation products. Many of them are low molecular weight compounds, which easily oxidizes and photoxidizes.
Onycha, along with equal parts of stacte, galbanum, and frankincense, was one of the components of the consecrated Ketoret (incense) which appears in the Torah book of Exodus (Ex.30:34-36) and was used in Solomon's Temple in Jerusalem. This formula was to be incorporated as an incense, and was not to be duplicated for non-sacred use. What the onycha of antiquity actually was cannot be determined with certainty. The original Hebrew word used for this component of the ketoret was שחלת, shecheleth, which means "to roar; as a lion " or “peeling off by concussion of sound." Shecheleth is related to the Syriac shehelta which is translated as “a tear, distillation, or exudation.” In Aramaic, the root SHCHL signifies “retrieve.” When the Torah was translated into Greek the Greek word “onycha” ονυξ, which means "fingernail" or "claw," was substituted for shecheleth.
Styrax is a genus of about 130 species of large shrubs or small trees in the family Styracaceae, mostly native to warm temperate to tropical regions of the Northern Hemisphere, with the majority in eastern and southeastern Asia, but also crossing the equator in South America. The resin obtained from the tree is called benzoin or storax, often used as a vanilla-like component in perfumery.
Benzoin or benjamin is a balsamic resin obtained from the bark of several species of trees in the genus Styrax. It is used in perfumes and some kinds of incense and as a flavoring and medicine. It is distinct from the chemical compound benzoin, which is ultimately derived chemically from benzoin resin; the primary active ingredient of benzoin resin is actually benzoic acid, not benzoin.
The Burseraceae are a moderate-sized family of 17-19 genera and about 540 species of woody flowering plants. The actual numbers given in taxonomic sources differ according to taxonomic revision at the time of writing. The Burseraceae are also known as the torchwood family, the frankincense and myrrh family, or simply the incense tree family. The family includes both trees and shrubs; its species are native to tropical regions of Africa, Asia, Australasia, and the Americas.
Storax, often commercially sold as styrax, is a natural resin isolated from the wounded bark of Liquidambar orientalis Mill. and Liquidambar styraciflua L. (Hamamelidaceae). It is distinct from benzoin, a similar resin obtained from the Styracaceae plant family.
Balm of Gilead was a rare perfume used medicinally that was mentioned in the Hebrew Bible and named for the region of Gilead, where it was produced. The expression stems from William Tyndale's language in the King James Bible of 1611 and has come to signify a universal cure in figurative speech. The tree or shrub producing the balm is commonly identified as Commiphora gileadensis. However, some botanical scholars have concluded that the actual source was a terebinth tree in the genus Pistacia.
Commiphora gileadensis, the Arabian balsam tree, is a shrub species in the genus Commiphora growing in Saudi Arabia, Yemen, southern Oman, Sudan and in southeast Egypt where it may have been introduced. Other common names for the plant include balm of Gilead and Mecca myrrh, but this is due to historical confusion between several plants and the historically important expensive perfumes and drugs obtained from them.
Stacte and nataph are names used for one component of the Solomon's Temple incense, the Ketoret, specified in the Book of Exodus. Variously translated to the Greek term or to an unspecified "gum resin" or similar, it was to be mixed in equal parts with onycha, galbanum and mixed with pure frankincense and they were to "beat some of it very small" for burning on the altar of the tabernacle.
The incense offering in Judaism was related to perfumed offerings on the altar of incense in the time of the Tabernacle and the First and Second Temple period, and was an important component of priestly liturgy in the Temple in Jerusalem.
Gum copal is a resin produced by the sap of forest tree in the genus Daniellia. Due to common impurities and differences in regions, gum copal ranges in color from black to yellow to white. Gum copal, along with ivory and slaves, was a significant export from East Africa in the 19th century. It can have an appearance similar to amber and may be mistaken for it. Unlike amber, gum copal is usually only 100–1,000 years old and it has not yet fossilized.
Mastic is a resin obtained from the mastic tree. It is also known as tears of Chios, being traditionally produced on the island Chios, and, like other natural resins, is produced in "tears" or droplets.
The incense offering, a blend of aromatic substances that exhale perfume during combustion, usually consisting of spices and gums burnt as an act of worship, occupied a prominent position in the sacrificial legislation of the ancient Hebrews.
Incensole is a C20 diterpene alcohol and biomarker for some plants of the Boswellia genus. It, along with its acetate ester incensole acetate, is an abundant component of frankincense, the resin collected from Boswellia trees. Incensole is used archaeologically to assist in identifying trade routes and distinguishing the identity of frankincense from other resins which may have been used together in incense and other salves. Incensole has also been deemed to be an active component in medicinal frankincense.