It depends if you are trying to create a tornado like vortex or merely keep yeast in suspension and promote gas exchange. If it's the latter, then a 3" Teflon coated stirbar will suffice. I prefer the octahedral ones with the pivot rings like this one. You can find them online or from one of the science supply vendors on ebay.
BTW, the stainless nail won't spin.
Last edited by johnsma22; 07-30-2007 at 12:05 AM.