Thomastik Special Rosin 205 Medium (Double Bass), ST-205II-ROSIN

Technical data

Sound and physics

Rosin (the residue left when turpentine is distilled from conifer resin) raises the static friction (the friction between two surfaces that are not yet sliding against each other) on the bow hair. The bow therefore carries the string along until the string's restoring force prevails; the string then slides back and grips once more.

The difference between static and sliding friction, to which rosin contributes, helps set the minimum and maximum bow force (the pressure of the bow on the string) between which a steady note forms. Within this range the string breaks away exactly once per vibration (Helmholtz motion), and the tone contains the complete series of harmonics (the whole-number multiples of the fundamental).

Frequently asked questions

Why does a bow need rosin?

Rosin raises the static friction between bow hair and string. The bow only carries the string for as long as that friction exceeds the string's restoring force, and the bowed tone grows from this alternation of gripping and sliding.

Do the numbers on rosin always indicate hardness?

That differs from maker to maker. At Thomastik 1, 2 and 3 stand for soft, medium and hard, while Lapella calls its grades Solid, Medium and Soft. Hidersine names its double bass rosins DB1 and DB2 by temperature, for cold and for moderate weather.

Where does the name colophony come from?

From the city of Colophon in Asia Minor. Colophony, or rosin, is the residue from distilling turpentine out of conifer resin.