In the late 19th and early 20th centuries Kauri gum ( semi-fossilised kauri resin ) was a valuable commodity, particularly for varnish, spurring the development of a gum-digger industry.
In terms of the test itself, the kauri-butanol value ( Kb ) of a chemical shows the maximum amount of the hydrocarbon that can be added to a solution of kauri resin ( a thick, gum-like material ) in butyl alcohol without causing cloudiness.
Since kauri resin is readily soluble in butyl alcohol but not in most hydrocarbon solvents, the resin solution will tolerate only a certain amount of dilution . " Stronger " solvents such as benzene can be added in a greater amount ( and thus have a higher Kb value ) than " weaker " solvents like mineral spirits.
resin of the kauri trees of New Zealand; found usually as a fossil; also collected for making varnishes and linoleum Synonyms: kauri, kauri copal, kauri gum,