To Stir Plate or Not To Stir Plate?

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balazs

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I've been making yeast starters for a while now using the conventional 1 gallon jug with an airlock and have been able to grow lots of slurry without a problem. Lately I have been looking into making a stirplate. I just can't help but wonder though, is this something that will really make a better and healthier starter or is it more or less another brew toy (eye candy). I am aware that the stirplate keeps the yeast in suspension but how much healther does is make the yeast?
 
I enjoyed making and using my stirplate. I honestly can't tell it it's making a real difference or not. If you aren't interested in it for the cool toys factor, then I'm guessing you can get good results by simply picking up the container and shaking or swirling for a few seconds each time you walk past it.

The stirplate basically just keep the yeast in suspension, allow it to contact more food than otherwise. Once you've shaken the wort up, you probably have as much O2 in solution as it can hold. There may be some further exchange of gas at the surface of the wort once the yeast start consuming the O2 already in the wort, but how much benefit a stirplate gives over occasional stirring is debatable.
 
A recent Basic Brewing Radio, may help you decide.

May 13, 2010 - Stir Plates and Triangle Tests
Home Brewer Sean Terrill joins us again to follow up on his yeast starter aeration experiment. Also, Sean shares the results of his pitching rate experiment, recruiting dozens of home brewers to help evaluate.

- Sean's Yeast Pitching Rate Results http://seanterrill.com/2010/05/09/yeast-pitching-rate-results/
- Sean's Stirplate Design http://seanterrill.com/2010/04/26/build-a-better-stirplate/

Click to listen- MP3
 
I liked making my plate as well. Awesome when it was done and worked!

If you check out MrMalty (http://www.mrmalty.com/calc/calc.html) and the suggested pitch starter needed, you will note that when you select stir plate versus simple starter, that the size of the starter goes down considerably the higher gravity beer you are making. I would say that this means stir plates are more effective at making healthy and more dense yeast colonies.
 
The point is that a stirplate will definitely create more healthy yeast in less time than a simple starter. However, I think the term simple starter means just adding your vial to a stationary jar of wort.

I can't help but wonder but that the occasional stir is also going to be more effective than simply letting it sit there undisturbed.

So the simple answer is yes, a stirplate is much better than nothing, but stirring a few times a day is probably very helpful too, as an alternative.

I recommend building one. It's easy and fun. I made mine out of an old printer selector box and an old computer fan. I used hard drive magnets mounted on the fan, and an old mobile phone charger to power the fan. It's crude, but it works.

There must be many threads in internet land that show people's stirplates. Lots of cool ideas.
 
I can't help but wonder but that the occasional stir is also going to be more effective than simply letting it sit there undisturbed.
Essentially what I found is that *frequent* shaking is almost as good as a stirplate, and that direct aeration is the best technique of all: Aeration and Yeast Starters

Overall it seems that agitation doesn't do much in and of itself (for a low-gravity wort, anyway). The benefit of shaking or a stirplate comes primarily from turning over wort at the surface and increasing oxygen uptake.

So the simple answer is yes, a stirplate is much better than nothing, but stirring a few times a day is probably very helpful too, as an alternative.
I think that's a pretty good summary.

Barazs: you say you're using an airlock, which means that there will be almost no oxygen available once the yeast have exhausted the O2 in the headspace. At that point reproduction will stop and you'll only have fermentation going on. Other techniques for growing more yeast won't be effective unless you remove the airlock.

Sean
 
Good stuff! Thanks for all the info and links. Definatly will be making a stir plate after reading more on what they do for the yeast.
 
...
I recommend building one. It's easy and fun. I made mine out of an old printer selector box and an old computer fan. I used hard drive magnets mounted on the fan, and an old mobile phone charger to power the fan. It's crude, but it works.

There must be many threads in internet land that show people's stirplates. Lots of cool ideas.

I'm with you, brother. Computer fan and some kind of 9V charger I found in the bottom of my drawer is all I used too. But I can only make stirplate starters about 2/3rds of the time because I keep losing the damn stirbar. Seems like the stirplate method makes way more yeast.
 
I'm with you, brother. Computer fan and some kind of 9V charger I found in the bottom of my drawer is all I used too. But I can only make stirplate starters about 2/3rds of the time because I keep losing the damn stirbar. Seems like the stirplate method makes way more yeast.

Tape a magnet to the outside of the flask after using the stir plate but before pitching.

Eric
 
Tape a magnet to the outside of the flask after using the stir plate but before pitching.

Eric

Ditto. I would love to do this but I forget to have a magnet handy when I go to pitch my yeast! I'm just careful.

if you are talking about the stir bar getting thrown by the fan, I use a 6V charger on a 12V fan with a potentiometer thrown in the mix. At the lowest setting it's a good stir. On high it can create a small vortex, but sometimes throws the bar off. There are all kinds of bars and magnet configurations to choose from. Chances are you can get something to work somehow.
 
If your magnet's strong enough you can also "walk" the stir bar up and out the neck to get it out of the way.
 
I wouldn't use a stir plate with an airlock on the flask. The main advantage of a stir plate is not just keeping the yeast in suspension, so much as creating an environment where O2 from the air can be absorbed by the wort, providing the yeasts with enough O2 to develop. This requires that O2 (or air) can enter the flask, but an airlock will prevent this. Much better to use some sanitized aluminum foil over the neck of the flask, or an inverted, sanitized jam jar that allows air in while preventing airborne bacterial from falling in.
Don't take my word for it, see http://maltosefalcons.com/tech/yeast-propagation-and-maintenance-principles-and-practices and take a look at the first chart.

-a.
 
A second stir bar is nice to have. Not just in case you lose/damage your main stirbar but also to hold the stirbar in the flask when pouring. They're just barely strong enough though (at least mine are).

This link posted by Revvy:
illustrates what Denny and others have been saying on this site for a while now; i.e. that poor head retention is often simply the result of poor fermentations.
 
The first time I used a stir plate, I noticed a massive difference in the quantity of yeast produced in my starter, and I used to shake up my (pre-stir plate) starters several times each day. I would never go back at this point.

If your magnet's strong enough you can also "walk" the stir bar up and out the neck to get it out of the way.

This is what I do as soon as I remove the flask from the stir plate. Otherwise, I will end up dumping the stir bar along with the contents of the flask because I'm an idiot and I will forget it's there. I store the keeper magnet by sticking it on one of the screws on the bottom of my stir plate, so it's easy for me to just turn off the stir plate, pull off the magnet, and use it to retrieve the stir bar all in one go.
 
James Spencer of Basic Brewing Radio and Video did a very nice job on the subject of stir plates versus other options, and if I remember the show accurately his guest determined that while stir plates do produce very good results you will receive even better outcomes by using an aquarium pump and airstone to agitate and aerate your yeast starter. But as others on the forum have noted, the "research" reported on BBR also demonstrated that periodically shaking the vessel in which your yeast starter rests works well too and costs less than stir plates and air stones/aquarium pumps. For me, the bottom line is that yeast starters are important, something I have not always acknowledged, and that you have at least three inexpensive and effective ways to produce them. I will probably focus on stir plates, mainly because they do provide one more homebrewing gadget to play with in my geeky world.
 
James Spencer of Basic Brewing Radio and Video did a very nice job on the subject of stir plates versus other options, and if I remember the show accurately his guest determined that while stir plates do produce very good results you will receive even better outcomes by using an aquarium pump and airstone to agitate and aerate your yeast starter. But as others on the forum have noted, the "research" reported on BBR also demonstrated that periodically shaking the vessel in which your yeast starter rests works well too and costs less than stir plates and air stones/aquarium pumps. For me, the bottom line is that yeast starters are important, something I have not always acknowledged, and that you have at least three inexpensive and effective ways to produce them. I will probably focus on stir plates, mainly because they do provide one more homebrewing gadget to play with in my geeky world.
 
This is obviously not data, just an anecdote, but in my last batch, I both used a stir plate for the first time, and I aerated my wort with an aquarium pump for the first time.

And this is also the first time I've ever had a blow-off. I've never seen such a vigorous fermentation. I'm definitely sold on using the stir plate.
 
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