Rosin

Rosin (/ˈrɒzɪn/), also known as colophony or Greek pitch (Latin: pix graeca), is a resinous material obtained from pine trees and other plants, mostly conifers.

[1] Rosin often appears as a semi-transparent, brittle substance that ranges in color from yellow to black and melts at stove-top temperatures.

Rosin also serves as an ingredient in medicinal and pharmaceutical formulations and can cause contact dermatitis or occupational asthma in sensitive individuals.

[12][13] Glycerol, sorbitol, and mannitol esters of rosin are used as chewing gum bases for medicinal applications.

[14] Occasionally, substances such as beeswax, gold, silver, tin, or meteoric iron[15] are added to the rosin to modify its stiction/friction properties and the tone that can be produced.

A cake of bass rosin left in a single position for several months will show evidence of flow, especially in warmer weather.

[1] The separation of the oleo-resin into the essential oil (spirit of turpentine) and common rosin is accomplished by distillation in large copper stills.

The essential oil is carried off at a temperature of between 100 °C (212 °F)° and 160 °C (320 °F), leaving fluid rosin, which is run off through a tap at the bottom of the still, and purified by passing through straining wadding.

Rosin varies in color, according to the age of the tree from which the turpentine is drawn and the degree of heat applied in distillation, from an opaque, almost pitch-black substance through grades of brown and yellow to an almost perfectly transparent colorless glassy mass.

The commercial grades are numerous, ranging by letters from A (the darkest) to N (extra pale), superior to which are W (window glass) and WW (water-white) varieties, the latter having about three times the value of the common qualities.

In this process, stumps and roots are chipped and soaked in the light end of the heavy naphtha fraction (boiling between 90 and 115 °C (194 and 239 °F)).

Upgrading of the rosin is carried out by clarification methods that generally may include bed-filtering or furfural-treatment of rosin-solvent solution.

The chief region of rosin production includes Indonesia, southern China (such as Guangdong, Guangxi, Fujian, Yunnan and Jiangxi), and the northern part of Vietnam.

[citation needed] The latter species is native to the southeastern U.S., but is now widely planted in tree plantations in China.

[22] Prolonged exposure to rosin, by handling rosin-coated products, such as laser printer or photocopying paper, can give rise to a form of industrial contact dermatitis.