Magnetic Stirrer Bar - B Series

These B series magnetic stirrer bars are PTFE-coated Alnico magnets with a moulded pivot ring. The ring means the bar spins on a small contact area rather than dragging its whole length across the vessel, so there's less friction and less chattering, and the stirring is more efficient. They're sold individually, in sizes from 6 x 4mm up to 100 x 10mm.

You'll also see them called magnetic stir bars, stirring bars or stirrer pills. They suit most applications and are usually used in flat-bottomed vessels such as beakers and conical flasks. The size code gives the dimensions, so B40 (40 x 8mm) is 40mm long and 8mm across.

Coating

Stir bars are usually coated in PTFE, which handles high temperatures and is generally chemically inert. For very high temperatures, or chemicals that PTFE isn't compatible with, glass-coated bars are available, and these also stand up to highly abrasive materials.

Magnet

The magnet inside is Alnico, an alloy of aluminium (Al), nickel (Ni) and cobalt (Co), which works for most jobs. Some stir bars use samarium cobalt instead. That couples more strongly with the stirrer's magnet and is less likely to spin out, giving more torque for large volumes or thick, viscous liquids.

Specifications

• Magnet: Alnico
• Coating: PTFE
• Pivot ring: yes, moulded
• Sizes: 6 x 4mm to 100 x 10mm (choose from the drop-down)
• Sold individually