Glass Stirring Rods: Cut and Flame-Polished

A laboratory stirring rod is a piece of solid glass, usually borosilicate, about half a centimetre thick and 10 to 40 cm long, with rounded ends. Rods are cut from a single long length of thin glass rod, and the ends are rounded, for example by flame polishing, so they cannot scratch the glassware: a scratched beaker or flask may crack when it is later heated. In flame polishing the glass surface melts briefly and surface tension pulls it smooth.