I'm sure all of us have seen the "how to make a magnetic stirrer" tutorials, however no one gives any way to make chemical resistant stir bars (most stir bars they suggest are nails or screws, which have Zn or Fe (or both) in them.  Unfortunately, this does not work for any reaction sensitive to those, or any reacting involve acids like HNO3 or HCl.  I thought about a few ways involving a nail, then coating it with teflon tape, but that would unravel while spinning.  Then I thought about finding pure teflon coating, but that is very expensive.  After brainstorming for a few more minutes, I looked down at my glass tubing and decided to try something.  I tried various combinations of nails and glass tubing, and found out that a 16d nail fits almost flawlessly inside standard 5mm glass tubing.

I had to spend a bit of time finding the right length of nail to work with my magnetic stirrer.  It has to be quite right, otherwise it will either be too heavy to spin, or could pull too strongly on the magnet (forcing the fan to move upwards and off it's spindle).  If it were too small, it would be inneffective for the size of vessel I might be using.

I used a hacksaw and cut the tip off the nail, then cut a 1/2" (~13mm) long section of the nail.  I guesstimated and broke off what I felt was the right length of glass tubing.  I used a blow torch to melt one side closed, then let it cool.  I slid the nail piece into the tube, then made any size adjustments to the glass one more time.  It's best to have as little air trapped in there as possible.  When you heat it up, and seal the end off, too much air can cause the glass to expand where it was heated and eventually break.  Overall, the glass tube melted to a length of 0.9 inches (~23mm), which works fairly well, but not perfectly.  I don't consider it worth it to make another, I'll just wait till this one breaks, then I'll make improvements on it's replacement.  That or I'll buy a real stir bar.  The downside of this stir bar is that you have to be very gentle with it.  I wouldn't even recommend dropping it into the flask.  Try to let it slide down the side if you can

Just a note on the teflon, you can get a spray to recoat the bottom of teflon pans for pretty cheep that may be of some use here.

The can I have is really old but Im sure they probably still sell something like it. It did have some sort of solvent in it and I also had trouble getting it to coat the pan but I was also suppose to take steel wool to it also which I didnt.

I can't find one and Iv gone thru three consumer product databases. I have to disagree chances are thats teflon. It reads the same as my older stuff did about just spray on and bake. Mine said right on the label that it was teflon. Chances are this is just a newer version of an older product.

Hmmmm, this is pretty weird. Do any of these provide a teflon coating?

http://dupontsearch.asp.dupont.com/search?q=teflon+dispersion+-lube&btnG=Search+DuPont&entqr=0&output=xml_no_dtd&sort=date%3AD%3AL%3Ad1&entsp=0&ie=UTF-8&client=en_US&ud=1&oe=UTF-8&proxystylesheet=en_US&site=default_collection

Ill get back to yall tommorow on it.. I have the can around still someware and a decent nose for solvents. Judging by the link though its more likely just really fine teflon that can be aerosoled

Oh I see, I didn't know it melted. I guess that makes sense that it would though I was just thinking it sublimated or something like that. Interesting spray regardless how it works.

Heres a thought that I will try very soon. It may not be a cure all but since many plastics are not reactive in most situations why not just make a thick goop using acetone with plastic and coat it with that for most synthesis?

clear shrinktubing

melt the end closed

not as universal as glass, but very effective

moose has sealed in JK thermocouples placed in HI\RP reductions, and it was re-usable a couple of times.