Stir plate effectiveness concern-maybe too small of a stir bar? - Home Brew Forums
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Old 03-09-2011, 08:32 PM   #1
crlova2
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Dec 2009
Lexington, KY
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When I make starters lately they are usually 1.5 liters minimum up to 3.2 liters. My concern is gas exchange (which I understand is a huge key in growing healthy yeasts during a starter) is not occurring as well in my larger starters. I used to get a visible whirlpool/vortex thing on the top level of the wort in the smaller starters on my stir plate which I would assume pulls air in. However, now that I have larger starters and the same stir bar I don't get that visible vortex anymore. Does this mean air isn't being pulled in and thus rendering my stirplate useless? Would a larger stir bar remedy this issue?



 
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Old 03-09-2011, 08:46 PM   #2
wyzazz
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Atwater, OH
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You don't need a swirling tornado of a vortex to have effective gas exchange, just the smallest 1/2" dimple in the surface of the wort is perfect.


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Old 03-09-2011, 08:49 PM   #3
crlova2
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Quote:
Originally Posted by wyzazz View Post
You don't need a swirling tornado of a vortex to have effective gas exchange, just the smallest 1/2" dimple in the surface of the wort is perfect.
The problem is that I don't get a dimple either the top of the wort in my erylenmeyer flask is flat...

 
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Old 03-09-2011, 09:05 PM   #4
remilard
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Nov 2008
Kansas City
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A bigger bar helps. I once purchased on ebay for about $20 three each of 9 or so sizes of stir bar. Only about 3 of the sizes are useful for starters but $20 for 9 bars I can use was a steal.

 
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Old 03-09-2011, 11:01 PM   #5
erikpete18
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Apr 2009
Seattle, WA
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I've seen the stir bars with the little ridge in the middle, they're supposed to spin a bit easier, might get more going for you. Really all you need is a convection current where wort at the top of the flask gets rotated to the bottom (and vice versa) and the yeast stays in suspension. As long as you've got the stir plate going and there's no airlock, you'll get plenty of aeration.

 
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Old 03-09-2011, 11:22 PM   #6
SD-SLIM
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Jan 2011
Fort Worth, Texas
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I would recommend getting a stir bar with a square profile, the square profile creates more turbulence and a lower rpm...the size will help somewhat, but the profile will make the biggest change. I believe Brewershardware.com carries these.

 
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Old 03-10-2011, 12:09 PM   #7
Chipster27
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Quote:
Originally Posted by SD-SLIM
I would recommend getting a stir bar with a square profile, the square profile creates more turbulence and a lower rpm...the size will help somewhat, but the profile will make the biggest change. I believe Brewershardware.com carries these.
Brewers has them so I replaced my round one with a square one and the sq on seems to work much better! The sq one also cured a noise issue I was having with the round one clanking around in my flask.

 
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Old 03-11-2011, 12:35 AM   #8
crlova2
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Dec 2009
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When you say square profile do you still mean a long cylindrical shape that just has square sides or one like this?

http://www.amazon.com/Nalgene-Magnet.../dp/B003OBZ2O6

 
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Old 03-11-2011, 12:36 AM   #9
crlova2
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or like this http://www.amazon.com/Dynalon-304455...d_sbs_indust_3

 
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Old 03-11-2011, 01:44 PM   #10
SD-SLIM
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Jan 2011
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Hello...those seem a little pricey for me but may work for you. I was referring to a stir bar that is just flat on top and bottom, similar to this one (http://www.northernbrewer.com/brewin...-stir-bar.html).



 
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