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Old 03-11-2009, 03:03 AM   #1
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Default Stir-Plate/YEAST Question!

I just finished my stir-plate...I will be using a 1000mL flask and a 1" stir-bar. Now I didn't have a hard drive magnet to use on the PC fan inside, so I bought some rare earth magnets from Radio Shack (little ones, 4 total). They are crazy strong, and I get a very nice swirl in the flask...but I do NOT get a vortex coming down more than a 1/4" or so. If I turn it up anymore, the stir-bar flies off track to the side.

My question, is that minute little vortex good enough? The starter is, as we all know, intended to propagate the yeast better by allowing them the O2 they need. Are they getting the O2 they need to be successful without the vortex? Is part of the equation simply having them in an active/suspended state so they do not just jump to the stage where they ferment the sugar and produce alcohol/CO2?

Insight is appreciated. I can adjust more or hunt down a bigger/better magnet if needed, but I am curious if this is sufficient.

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Old 03-11-2009, 03:05 AM   #2
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i would suggest having this moved to the DIY section. If its the rare earth magnets available at my radio shack, they were far to small for me to keep a good vortex. Check out the thread link in my signature to see what others have done.

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Old 03-11-2009, 03:20 AM   #3
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How many magnets did you use? I haven't built my plate yet and was looking for an easy source for some magnets wondering if 4 of these would possibly work. If there is room to fit 4 on a fan anyway.

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Old 03-11-2009, 03:45 AM   #4
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All you really need is to keep the yeast in suspension. If you're getting a good dimple like that, it's probably just fine.

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Old 03-11-2009, 03:52 AM   #5
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This isn't about the build, so why DIY?? It's about what yeast need to propagate properly and the amount of O2 needed for them to do so. Please move it back to the other forum. The "gurus" of starters don't spend all their time in the DIY forum, they are in the tech forums. Thanks. Edit my title if needed to convey the content of this thread better please.

I've seen that thread, and modeled mine somewhat after it. I used those little ones from Radio Shack that are in a 2 pack for about $2. I used 4 total.

So, gurus...is it simply being in suspension that they need, or the extra surface area created by the vortex for them to get more of the O2??

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Old 03-11-2009, 04:06 AM   #6
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I aerate my starter before throwing it on my stirplate. No need to have a Category 5 funnel in the flask. I think you referred to it as a "dimple", that's all you really need. At this point, the stirplate is mainly to keep the yeast in suspension and active, not really to aerate your starter.

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Old 03-11-2009, 10:41 AM   #7
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Quote:
Originally Posted by rsmith179 View Post
I aerate my starter before throwing it on my stirplate. No need to have a Category 5 funnel in the flask. I think you referred to it as a "dimple", that's all you really need. At this point, the stirplate is mainly to keep the yeast in suspension and active, not really to aerate your starter.
Actually it's a combination of both. You want to aerate the starter and keep the yeast in suspension. I'm assuming that the movement of the wort exposes more of the wort to the air, allowing more absorption. In any event, movement is what you are looking for, a huge vortex is not needed.
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Old 03-11-2009, 01:02 PM   #8
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As for the DIY half of this discussion, I'd play around with the placement of your magnets. Try moving them radially outward on the fan so that the ends of the stir bar line up with the center of the magnets. If that doesn't work, move them in our out and see what works for your setup. Also, play with the height of the magnets / the gap between the flask. And make sure you have the magnets flipped right so the polarity isn't conflicting.

I use 2 rare earth magnets, probably similar to yours, with the micro stir bar from Northern Brewer. I'm able to create a huge vortex which sucks air all the way down to the stir bar...not that I'd be running it that way for my starters. It took some time tinkering with the setup, and I'll tweak it every once in a while. I didn't epoxy or permanently mount my magnets to the steel washer that I attached to the fan (with 3M double-sided tape) so I can make slight adjustments when necessary.


At least if you have the option of increasing the speed and making a nice vortex, you can do so once you arrive at a conclusion for the yeast suspension/aeration question.

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Old 03-11-2009, 01:22 PM   #9
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I would add, based on my understanding of the yeast cycle that just keeping them in suspension is not enough for this process. Unless I have been miss-informed I believe you want to keep as much O2 mixed into the solution as possible as the availability of O2 is what keeps the yeast in the reproductive stage. When they run out of available O2 they switch to a feeding stage and produce alcohol and CO2 until they choke themselves out and go dormant.

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Old 03-11-2009, 01:33 PM   #10
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Quote:
Originally Posted by freddyb View Post
As for the DIY half of this discussion, I'd play around with the placement of your magnets. Try moving them radially outward on the fan so that the ends of the stir bar line up with the center of the magnets. If that doesn't work, move them in our out and see what works for your setup. Also, play with the height of the magnets / the gap between the flask. And make sure you have the magnets flipped right so the polarity isn't conflicting.

I use 2 rare earth magnets, probably similar to yours, with the micro stir bar from Northern Brewer. I'm able to create a huge vortex which sucks air all the way down to the stir bar...not that I'd be running it that way for my starters. It took some time tinkering with the setup, and I'll tweak it every once in a while. I didn't epoxy or permanently mount my magnets to the steel washer that I attached to the fan (with 3M double-sided tape) so I can make slight adjustments when necessary.


At least if you have the option of increasing the speed and making a nice vortex, you can do so once you arrive at a conclusion for the yeast suspension/aeration question.
Any pics of your magnets so I can get an idea what the spacing should be? I played with them for hours trying to get a vortex, and no luck. I've got them within just a few mm of the top of the enclosure, and that made all the difference in the world, but it's still not enough I guess. The bar seemed to stay in that spinning pattern to higher RPM when the magnets were in towards the center a bit more. Putting them out farther seemed to throw it off easier.

I did have issues with polarity, but have it fixed now. Two on one side are +up, and the other two are +down (N vs S, whatever). Any more input is appreciated!
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