Random problem here... I went to use my stir plate to make a starter tonight. It's probably been about two months since I last used it. Over that two-month period, I stored the stir bar in a baggy along with the little magnet that came with the stir plate which you use to hold the stir bar in place while pitching yeast. For a frustrating 5-10 minutes I tried to get the stir bar to attach to the stir plate to start my vortex, but the darn thing kept flying to the side of my erlenmeyer flask. After a few minutes, I started to realize that I must have reversed the polarity of the stir bar by storing it along side another magnet. Is there a quick way to re-reverse the polarity, or do I just need to go buy another stir bar and revert to the swirl method for this starter in the meantime?
Even if you had reversed the polarity (unlikely), I don't see why that should make a difference. The bar should automatically flip around to the correct orientation. Is the bar actually flying to the side before you even turn the motor on?
??? Magnets are not monopolar, if that's what you mean. But the terms north and south describe the polarity of the magnet.
I was thinking a weakened field also, but I don't think that would explain the bar being thrown if the motor hadn't been turned on yet.
I don't know why I didn't think of this before, but I fished the bar out and put it directly on the stir plate. It worked perfectly. I dropped it back in the flask, and it immediately connected up and started spinning like normal. I'm not sure what my issue was before. It's been one of those weeks....
Is it possible that the rheostat on your stir plate was set too high? On mine, if it is turned a hair higher than "just right" the stirring mechanism seems to spin too fast for the magnet, which slides to the wall of the flask and bounces around awkwardly, off center, creating no vortex.
I turned it way down while trying to get it connected, and was still struggling. It just wasn't my night. Oh well...the humility is good for me.
I have one of those cheapo stir plates and it has seemed lately that my stir bar shoots to the side more than it used to when making starters. Not sure if the magnets are weaker or I am more heavy handed with the "volume control". Maybe I will buy another stir bar and see if that gets me back...
This is a pretty common issue actually. It is called operator error. Not really any way to avoid it except for swapping out the operator for something higher-end. Training can occasionally help with this issue, but in my experience, you are better off just chucking the operator and installing a new one.
haha... Definitely would not rule that out, but I've been making starters for years on the plate and have noticed the frequency of spin outs increasing.
