Magnetic Stirrer

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Magnetic Stirrer

Postby andytv » Wed Aug 28, 2002 5:48 am

I ordered a magnetic stirrer, it just arrived, and its on my desk. How does it work? I put a jar of water with a little pepper on it and cranked it up; it doesn't look like its causing the mixture to swirl. Is it supposed to? A tossed a pushpin into the jar and it is very happily spinning. Am I missing something? Do you need some sort of metal device in the jar?

Andy
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Mag Stirrer

Postby MartyL » Wed Aug 28, 2002 7:30 am

You need the teflon coated magnet/rod about 1/2 inch long, that should have come with the stirrer. Place it gently in bottom of flask, add ingredients and slowly turn knob up to the desired speed. The liquid will stirr from mild to hurricane with these stirrers. If you don't have the proper stirring rod, morebeer.com has them in pairs. Good luck.
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Feeling stupid

Postby andytv » Wed Aug 28, 2002 9:53 am

I feel a little stupid right now. I was envisioning some sort of convection effected by a magnetic field. Now I know its much simpler than that. I ordered a stirrer from McMaster Carr this morning. The reason that the rod wasn't included is that the stirrer is used (ebay - $10). Ok now the good question becomes; How fast is fast enough?
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Stir it

Postby Freon12 » Wed Aug 28, 2002 12:43 pm

Hi andy, I use the fastest speed to introduce air into the mixture for feeding yeast at the begining of the starter. I use a med. type speed just to keep the yeast suspended and active.
You will love this toy! Watch out for that first batch made with this starter, remember my stained walls?
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What Size Stirrer?

Postby andytv » Wed Aug 28, 2002 1:15 pm

So your the one who planted this seed in my head. I rememeber your posting; It's the reason I bought the stirrer. I plan on resting my 2litre erlenmeyer atop this new toy. The base of the flask is at least 8 inches, which has me wondering if I ordered the right size stirring rod. I ordered a 2" long TFE rod, with a ring molded onto the center. Will this be too big, too small; or can I achieved results w/ any stirrer using speed variation?

Also; for all of you who are thinking for buying one of these things; ebay was packed w/ new & used.

Andy
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Cheap

Postby Freon12 » Thu Aug 29, 2002 4:47 am

I'm sorry I caused money to leave your pocket, that's almost a homebrew sin. Hee, Hee.
I have a 1/2" tfe rod and the stirer is 6" X 6" and it works with both the 1 ltr and 2 ltr flasks.(step up at second feeding) Although with the larger flask I must center the rod and start it up slow. I found Kimax flasks to be high quality and low priced. Trust me, you will love this thing-How about air lock movement in 2-4hrs!

Cheers
Steve.
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what is it?

Postby stouts » Fri Aug 30, 2002 6:57 pm

never heard of a mag stirrer, whats is it and when is it used during fermentation? jay
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Starters

Postby Freon12 » Sat Aug 31, 2002 6:56 am

I was having trouble with how long it took my beer to start fermenting using a tube of whitelabs yeast. The yeast was dying in shipment during warm weather. Well you know us, and I set out to fix this problem. I surfed around and found information on feeding yeast and making them viable and multiply 6-8X faster than any other way I found. I use a 1000ml erlymer flask, you know, the ones from chemistry class. 1/4 cup of DME, a pinch of yeast nutrient mix and a small amount of hop pellets added to 500ml of water in the flask with the stirrng tablet.
Boil slowly(watch for boil over)for 5 min. and cap off the flask with a stopper and glass air lock(plastic will melt) and remove from heat.
Put the flask in ice and cool to 70f. Add the yeast and place it on the stirrer base. Turn on the stirrer and the tablet will begin to move faster and faster until the liquid is moving. The base will make the tablet you boiled spin. Let it ferment and pitch in your wort when the yeast is at full foam.( I say everyone into the pool).
I also use this to make multiple batches of beer with one yeast purchase. I "step up" the above mixture by using a 2000ml flask and 1/2 cup DME and use as above. When it cools I put the contents of the 1000ml flask into the 2000ml tablet and all. Srir the bigger flask and you will have yeast coming out of your ears(or fermenter). This is very key to making barley wine or triples. Oh you fruggle homebrewers, stretching yeast dollars like that.
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Stirrer Caution...

Postby Mesa Maltworks » Sun Sep 01, 2002 5:27 am

When I established my commercial brewing laboratory, I bought 3 large stirrers to stir 10 - 15 gallons (Corning )and a 3 small ones to stir 125 to 2000 ml flasks (Hanna). On my first propigation, I placed the propigate media, a single cell of my culture yeast and the mag bar in a 125 ml. flask. I waited the requisite 24 hours and.... NOTHING ! Reason: Friction causes heat and the motor doing the work does as well!!!! I killed the poor !@#$ ! So, when using small volumes of liquid on stirrers, elevate the flask on something to keep the base from direct contact with the top of the stirrer. The potential that this problem can occur is greatly reduced once the volume is 1,000 ml and over, but depending on your stirrer model, it is a good precaution to take anyway. On the larger models, this is not an issue because the resting plate is suspended above the motor's housing which is also usually ventilated.

Also keep in mind that you don't want to let the media go above 75 degrees F while propigating. If you do, cell morphology will be effected and their metabolic characteristics will therefore be modified possibly leading to unpredictable results.

Eric the Yeast Murderer
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