How is rosin for string instruments made and what discerns quality?
In: Technology
Rosin, or Resin is a solid obtained from the sap of various species of trees, mainly conifers such as pines or firs.
Traditionaly, the sap was harvested by carving the bark of the tree in a series of v-shaped cuts, then placing a collecting jar at the base of the grooves. The collected sap was then heated in a closed vessel to evaporate turpentine. Historically, turpentine was a valuable solvent and cleaner. The leftover solids are rosin. Different trees produce rosin with different qualities. The heating process also alters the properties of the rosin depending on how it’s carried out.
Rosin can also be recovered as a byproduct from the paper making process. Various stages in the process separate oily compounds from wood chips which would contaminate paper produced thereby.
However, high quality rosin used for traditional arts and crafts such as violin bows is usually extracted from stumps of conifer trees, the rest of the tree being used for lumber. The stumps are cleaned and chipped. The chipped material is rinsed with a light solvent which dissolves resin particles. The solvent is then heated to evaporate it leaving the extracted rosin behind. Further chemical processing using different solvents can separate different chemical constituents in the rosin producing different grades.
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