Stirring Rods and Stir Bars
A stirring rod and a stir bar are tools used to mix liquids for thorough blending and to speed up chemical reactions in solutions. Stirring rods are long cylinders made entirely of glass or plastic. A glass stirring rod may be made of borosilicate or flint glass. Inducing crystallization and aiding decanting are additional uses for a plastic or glass rod. Stir bars have a glass or plastic casing around a magnet, and are used with a magnetic stirrer. Certain models have an FDA-approved polytetrafluoroethylene (PTFE) casing for use in food, drug, and cosmetic applications. A magnetic stir bar, or spin bar, is available in various shapes and sizes, and may have a pivot ring to reduce friction and improve spinning. An octagonal shape creates a stronger vortex than round or cylindrical shapes. Cross or star shapes spin with greater stability and less vibration. Cell shapes produce minimal vortexing and are typically used in cuvettes.