Colophony

resin obtained from conifers, especially pines. Cleaned and freed from water and essential oils, it is a brittle, brownish or yellowish substance. Note that rosin is a specific type of resin. Not all resins are rosins.

It chiefly consists of different resin acids, especially abietic acid.

Colophonium has various applications, including:

• treatment of the bow of a string instrument
• use as flux (metallurgy) for soldering: The tin-lead solder commonly used for electronics has about 1% colophium as core which acts as flux agent, i. e. it facilitates getting a well conducting non-oxidized connection.
• as ingredient in printing inks, varnishes, glues and chewing gum
• in former times, as medicine
• in sports:
  • Ballet slippers are rubbed in powdered rosin to reduce slipping.
  • Baseball pitchers use a rosin bag to keep their hands dry. Usage of rosin is specifically mentioned in major league baseball rules
• as main ingredient of a powder used to polish glass when making optical instruments such as lenses (Also, amateur telescope makers use a polishing lap made from rosin to polish and figure telescope mirrors and lenses.)

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Colophony also is the name of a Ionic city, from which the resin got its name.