How Are Tree Resins Gathered?
Trees have a system of resin ducts lined by cells that produce many kinds of chemicals, including resins. The tree makes these complex chemicals as a defense against invaders such as insects, bacteria and fungi and against freezing temperatures. People have gathered tree resin for thousands of years. Some old extraction methods are still used, but newer methods have been developed. Pine trees are commonly used for resin extraction, but many other species also produce resins. Does this Spark an idea?
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Resin Types
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Resins are used in hundreds of compounds including coatings, flavorings, medicines, incense, plastics and adhesives. Resin is chemically different from latex and gums, which are produced from the breakdown of cellulose. Resins can be divided into three groups -- hard resins, oleoresins and gum resins. Hard resins have a low oil content, so they harden quickly. Oleoresins have a high oil content, so they are liquid. Gum resins are mixtures of gum and resin and look milky.
Tree Tapping
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Gum resin is extracted by a process called tapping. A living tree is cut and the resin flows out of the wound. The cut is a rounded V shape with the point of the V lower so resin flows to the point and into a collection container. Two major products are made from pine tree resin: Turpentine is distilled from resin with rosin left over. Rosin is used in soap, disinfectants, adhesives and perfumes.
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Pulp and Stumps
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Resin can also be extracted from wood chips and tree stumps after the whole tree is harvested. The chips are turned into a pulp and the resin is extracted chemically using a sulfur compound called sulfate. Tree stumps can be crushed and the resin can be extracted with solvents. Both of these processes require machinery to do the extraction and destroy the tree. Tapping leaves the tree alive and can be repeated yearly.
Insect Extraction
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Shellac is made from a material that is extracted from the resin of several tree species. An insect, called a lack insect (Tachardia lacca), feeds on tree sap and excretes the resin part of the sap. The lack insect uses these resin secretions to spin a cocoon-type covering to protect it from predators. The resin secretions are collected and processed into shellac, which is used as a clear finish for wood. Shellac is not waterproof.
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