The Incredible Uses of Resin: From the Ancient Egyptian Mummies to the Swan Lake Ballerinas
What is Resin?
Resin is a viscous and aromatic hydrocarbon secretion of many plants, most notably coniferous trees. Resin is a colloid in which the liquid solvent, turpentine, is a mixture of various volatile compounds, called terpenes, and the non-volatile solid compounds compose a waxy mixture, called rosin, that is obtained by distillation of the volatile compounds. Some resins when soft, thus less viscous, are known as oleoresins, and when containing benzoic acid or cinnamic acid they are called balsams. Both turpentine and rosin are very useful products that can be used in a variety of ways. Their economic importance is such that it has driven human development through different times in many regions.
Why it is produced?
Resin is produced in specialized cells that line the resin ducts found throughout the plant body or in some specific parts such as leaves. The needles of conifers contain resin canals, or ducts, usually two or as many as 20 in some species. The ducts are typically lined with several layers of epithelial cells, thin-walled on the interior and thicker on the outside. There is no general agreement on why plants produce resin. Some authors consider it as a waste product, resulting from plant metabolism. But, it is well known that resin serves as an active and efficient defence mechanism against attack by bacteria, fungi, insects and grazing animals, which could take advantage of wounding in conifers, notably in pine. When the bark is wounded, resin pools out and when exposed to air it polymerizes and forms a protective layer, thus sealing the wound. This process can be quite fast as a response. Insects may be trapped in this resin ooze, which, when fossilized, becomes amber. Resin serves also as the main repellent of tree-killing bark beetle that is a tremendous problem for conifer forests in North America, causing millions of dollars of damage annually. Some resins may be toxic and disrupt the feeding, digestion or metabolic function of the attacker. However, a number of insects specialized in feasting on pine needles; hence by circumventing and tolerating the resin defence they have managed to transfer the anti-predator effects of the resin itself and use them on their benefit as a defence against predators. The system of resin ducts, due to its conspicuous nature in the plant body, likely remains advantageous because it facilitates rapid, widespread and contained delivery of the protective agents throughout the whole plant body. In the tropical regions and in hot and drier areas specifically, resin can also serve as a mechanism for protecting plants against drought and water losses. The leaves and buds of some species that grow in arid regions are covered with resin. This not only minimizes the water loss by evapotranspiration but also can reduce the leaf tissue temperature by increasing the reflectivity of the light that hits the leaves.
Resin Economic Importance
In Europe, harvesting pine resin dates back to Gallo-Roman times and today it is still a considerable fraction of the forest industry associated to pine, besides the paper industry and wood. Similarly in all plants that produce resin, it is obtained by tapering the tree so to force the tree to "bleed" continuously as a result of wounding. China and Indonesia dominate the world production and market for the last three decades, taking Portugal’s place as the world producer. These three countries along with Brazil produce more than 90% of the rosin and turpentine in the world, obtained mostly from several pine species. There is also a large industry centred in the Southern United States and in the South of France (where maritime pine is the main source of resin) that is devoted to resin extraction and refinement. Turpentine and rosin are often called naval stores, a term that originated when the British Royal Navy used large amounts of resin for caulking and sealing their sailing ships and for waterproofing wood, rope, and canvas. In USA, most naval stores come from two pine species: Caribbean pine (Pinus caribaea) and slash pine (Pinus elliottii). Pines resin was also already used by Mediterranean sailors of ancient Greece, Egypt and Rome. Egyptians also sealed their mummy wrappings with pine resin, and the Greeks lined thei clay wine vessels to prevent leakage. Today, pine flavour is still added to Greek wines giving retsina (Greek wine) its distinctive flavour.
Turpentine is the premier paint and varnish solvent, and is also used to make deodorants, shaving lotions, drugs and limonene – the lemon flavour in lemonade, lemon pudding and lemon meringue pie, in the food industry. (Yes that is right, you can do lemonade without lemons.) Ballet dancers dip their shoes in resin to improve their grip on the stage, and violinists, viola and cello players drag their bows across blocks of it to increase friction with the strings and help to make the unique sounds of their instruments. Baseball pitchers use resin to improve their grip on the ball. Incense, a mixture of different rosins from several plant species, is still widely used and not just for religious ceremonies. Some resins are used and chewed as gum and are still a very popular natural chewing gum. But that is for another hub. Finally, the most valued resin product is amber, fossilized resin, which has been used since early ages on jewellery and can give us quite valuable information from the life (pre-historic insects mostly) that has been trapped in its famous lumps (remember the bug from Jurassic Park?).
Traditional Resin Extraction in the Southwest of France, Gascony
Portugal and Southwestern France (Gascony) where maritime pine grows
Resin extraction in USA - part 1
Resin extraction in USA - part 2
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