Rosin (), also called colophony or Greek pitch ( la, links=no, pix graeca), is a solid form of resin obtained from pines and some other plants, mostly

conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extan ...

, produced by heating fresh liquid resin to vaporize the volatile liquid terpene components. It is semi-transparent and varies in color from yellow to black. At room temperature rosin is brittle, but it melts at stove-top temperature. It chiefly consists of various resin acids, especially

abietic acid Abietic acid (also known as ''abietinic acid'' or ''sylvic acid'') is an organic compound that occurs widely in trees. It is the primary component of resin acid, is the primary irritant in pine wood and resin, isolated from rosin (via isomerizat ...

. The term ''colophony'' comes from , Latin for "resin from Colophon" ( grc, Κολοφωνία ῥητίνη, Kolophōnía rhētínē), an ancient Ionic city. It is an

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food s ...

approved food additive.

Properties

Rosin is brittle and friable, with a faint piny odor. It is typically a glassy solid, though some rosins will form crystals, especially when brought into solution. The practical melting point varies with different specimens, some being semi-fluid at the temperature of boiling water, others melting at . It is very flammable, burning with a smoky flame, so care should be taken when melting it. It is soluble in

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

, ether, benzene and

chloroform Chloroform, or trichloromethane, is an organic compound with chemical formula, formula Carbon, CHydrogen, HChlorine, Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to ...

. Rosin consists mainly of

, and combines with caustic

alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...

s to form salts ( rosinates or pinates) that are known as

rosin soap Rosin (), also called colophony or Greek pitch ( la, links=no, pix graeca), is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vaporize the volatile liquid terpene comp ...

s. In addition to its extensive use in soap making, rosin is largely employed in making

varnish Varnish is a clear transparent hard protective coating or film. It is not a stain. It usually has a yellowish shade from the manufacturing process and materials used, but it may also be pigmented as desired, and is sold commercially in various ...

es (including fine violin varnishes), sealing wax and various

adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...

s. It is also used for preparing shoemakers' wax, for pitching lager beer casks, and numerous other purposes such as providing backing surfaces to tin ware, copper ware, or even silver and gold vessels when embossing or engraving them. Its relatively low melting point, and firm solid form allows liquid rosin to be poured into the vessel, and when cooled allows embossing or engraving of the vessel without deforming the vessel - even if it has a skin which is quite thin. Afterwards, the object can be reheated in an oven, and the rosin poured out for reuse. Any remaining rosin film can easily be rinsed away with alcohol or other solvents. Rosin is also sometimes used as internal reinforcement for very thin skinned metal objects - things like silver, copper or tin plate candlesticks, or sculptures, where it is simply melted, poured into a hollow thin-skinned object, and left to harden. Prolonged exposure to rosin fumes released during soldering can cause occupational asthma (formerly called ''colophony disease'' in this context) in sensitive individuals, although it is not known which component of the fumes causes the problem. The type of rosin used with bowed string instruments is determined by the diameter of the strings. Generally this means that the larger the instrument is, the softer the rosin should be. For instance, double bass rosin is generally soft enough to be

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