Originally Posted by ekjohns
I am building some stir plates and have read about people using different sizes and kinds of stir bars. So far what I have read is that 1" stir bar seems to work better than any other size. I have also read that the ones with the ring in the center make alot of noise and easily get tossed. Finally I have read that someone used an egg stir bar (shaped like a football) and it worked better than anything including the 1" standard stir bar. Assuming the magnet is from a HD, what have people found to be the best?
Either the egg, or a stir bar with a central pivot ring should work better than a plain stir bar. The plain ones have a lot more surface friction than those pivoting on a central point, and so they tend to get thrown as soon as you approach higher rpms.
Another thing to look out for is the material of your stir bar. Some stir bars are just iron coated in teflon. Others will actually have a NdFeB core that is coated in teflon. This makes a huge difference in the magnetic coupling with your stir plates magnets. I've tested iron stir bars against NdFeB ones, and where the iron kicks out of rotation at a small dimple, the NdFeB will stay in rotation and create a vortex reaching all the way down to the base of my flask.
Personally, I use a 1.25" NdFeB stir bar, hexagonal profile with a pivot ring.
*Edit* My bad, I realize I am replying to this years after the fact. Sorry to stir up old threads. Somehow it popped up in the forefront of my forums, and I had 2cents to throw in.