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AnOldUR

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Well, it looks like I get to retire the lazy susan that I've been using to keep the yeast active in my starters. Worked fine, but I was never thinking the yeast was getting the oxygen that it craved. Picked up this well used, lab quality stir plate on eBay for $22. It’s got a little corrosion from who knows what chemicals, but works fine.

My question is about the vortex and how fast the bar should spin. Should the vortex come just down to the stir bar, just above it or fully engulf the bar?

StirPlate01.jpg
 
I've never used one,but the purpose is just to keep the starter mixing. So as long as it is all swirling around it should be fine.
 
So, I'm bumping this to get some opinions on the size of the vortex.

Just made a starter, but had some thoughts about the process. Normally I would shake the crap out of the wort to aerate it, but figured that with the stir plate it wouldn't be necessary. Didn't even mix after adding the yeast. Just threw in the bar and cranked it up. Is this normal practice when using a stirrer?

New toys are so much fun :ban:


Edit:
Watching the vortex is almost as hypnotic as staring at an airlock. :cross:

FirstStirPlate.jpg
 
I haven't done enough to say normal practice...

I still aerate mine, shook the heck out of it. I agree part of the reason for the stir plate is to keep it oxygenated. I just made a 1.5 liter one for some kolsch yeast and spin it fast enough to see a few bubbles going in suspension.

I probably keep the tin foil too tight for any air exchange so I like to take it off and put it back every 4-6 hours when I'm awake. My plan is to pitch it at high krausen tomorrow afternoon if the brew days goes off w/out a hitch.
 
Beating a dead horse (or do I just like to post pictures)? :confused::D:eek:

Found a useful Q&A (posted below) and followed the advise.
The interesting thing is that the vortex gets smaller as the yeast grows and then returns to the original size when growth has stopped.

It worked!
(even though I dumped the stir bar into the carboy,
I know, I know, use a magnet to hold it back. :eek:)
BavarianWheat1.jpg


Stir Plate FAQ by Johnm42 (thanks to CJinJ and Beershasta for their help)

Q. How much would I spend for a stir plate?
A. For under $30, you can build your own stir plate. For anywhere from $30 to $100, you can find many good used and some new stir plates.

Q. Will it help my brewing?
A. Most definitely. The stir plate will keep your yeast constantly suspended. This will benefit the yeast in several ways. First, in the early stages, it will help provide the wort and yeast with extra oxygen, especially if you leave the container loosely covered and/or bubble filtered air through it. Second, once the yeast starts fermenting the starter wort, the stirring action will knock the CO2 out of solution, leading to healthier yeast. And third, the yeast will stay in contact with the sugars in the wort for a longer time. The result of all this is that the yeast will produce more and healthier cells, which will reduce, lag times and ferment further and faster.

Q. How do I use a stir plate?
A.
1.Place a magnetic capsule in the starter before boiling. The 1-inch capsule is fine for a 1L flask while the 2-inch works well for most anything else that finds its way to the stir plate. The 3-inch is a little large and tends to be "thrown" out of the center fairly easily.

2. Check that the motor is off. Tilt the container so the capsule goes to the lowest part, carefully return the container to horizontal, set what was the lowest part on the center of the stir plate and slide the container to the center of the plate. Usually, you'll hear the capsule sliding.

3. Turn on the plate at low speed until the liquid is obviously rotating. If you hear the motor turning but don't hear the capsule turning, repeat step 2. If you hear the capsule turning but don't see motion, turn up the speed a little.

4. When you see motion, slowly in steps increase the speed until you have a fairly wild vortex. Leave it for 10 minutes so the wort can absorb O2. It will do so quite efficiently. If you should "throw" the capsule by turning it too high, start over at step 2.

5. After aerating the wort, pitch the yeast and reduce the speed so there is a nice vortex. Leave a cover on the container loosely for good gas exchange. A sanitized piece of aluminum foil, folded over once or twice to give it extra strength, works fine as a cover.

Q. How long does it take to complete the starter?
A. Most starters will finish in 24 hours. Even a 4L starter takes only 24 hours. Generally, you can tell when the starter has finished by watching the speed of the swirling. Early in the process, the wort will be swirling quite quickly. Once the yeast starts fermenting, the swirling will slow down and the wort will appear muddy and thick. When the yeast is finished, the swirling action will speed up again. That's when it's done.

Q. What do I do then?
A. Pitch the yeast right away, if you are ready for it, or put it in the fridge and let the yeast settle out overnight. You can keep the starter for at least a week or two. Pour off most of the spent wort, stir the yeast cake into the small amount left and pitch the yeast slurry.

Q. Are there any more handy tips about Stir Plates?
A. Why, yes!
1. You can also use O2 if you use it to oxygenate in your flask during that initial aeration period. I do this. I place my O2 line in the flask and run a measured amount while the "wild" vortex is active.

2. You can build up starters for lagers by following the instructions once and then placing the starter in a refrigerator. The next day, make another starter, decant the top fluid off your previous starter and pitch the new starter "fuel" on top and re-follow the same steps. This way you basically have a cell count that is double the standard amount of the normal one.

3. At pitching, you can use a magnet and pull the stir bar to the side of the inside of the flask. This way when you pitch, your stir bar won't fall into your wort. You can also note that an extra stir bar is useful incase one goes into your wort. This would make your stir plate useless until your beer is finished fermenting.
 
I don't make a vortex all the way down to the stir-bar usually. I just get the wort moving and have a 1-2" deep vortex. The point is to get the wort all exposed to the oxygen in the container, then it also keeps the yeast in suspension so they'll keep growing and budding off new yeast cells.

I still contend that you will get the same amount of yeast growth with an air-lock as you would with aluminum foil. You are not doing much gas exchange with foil wrapped over the top anyway. If you think about it inside 2 liter flask with 1 liter of wort you have 200,000ppm oxygen. Wort needs 8-16 ppm oxygen for optimal yeast growth. So even as the yeast put off Co2 the wort is swirling so the air above the wort is still swirling, mixing the co2 and air. This keeps the co2 blanket from forming so the wort can take up more oxygen as it is depleted by the yeast.
 
I still contend that you will get the same amount of yeast growth with an air-lock as you would with aluminum foil. You are not doing much gas exchange with foil wrapped over the top anyway. If you think about it inside 2 liter flask with 1 liter of wort you have 200,000ppm oxygen. Wort needs 8-16 ppm oxygen for optimal yeast growth. So even as the yeast put off Co2 the wort is swirling so the air above the wort is still swirling, mixing the co2 and air. This keeps the co2 blanket from forming so the wort can take up more oxygen as it is depleted by the yeast.

You would really need to do cell counts and look at the yeast under a microscope to verify which is the "best" way. I know that for me, it's infinetly easier to sanitize a piece of tin foil then it is to track down a stopper and airlock, so if it's better for the yeast, awesome. If it's the same for the yeast, awesome. :rockin:
 
You would really need to do cell counts and look at the yeast under a microscope to verify which is the "best" way. I know that for me, it's infinetly easier to sanitize a piece of tin foil then it is to track down a stopper and airlock, so if it's better for the yeast, awesome. If it's the same for the yeast, awesome. :rockin:

Works for me. I don't have the equipment to properly test it, I know both ways work. I always use aluminum foil as well, a lot easier. I just think that it is a bit overhyped that you can't use an airlock on your starter and get good yeast growth.
 

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