Stir bar spins but no vortex - is it still stirring?

[gkeusch]

I have a Stir-starter plate with 3/4" bars. It creates a nice little vortex in a 1 L E. flask but now I got a 2 L E. flask; the bar spins fine but no sign of vortex. If it is spinning then is it still stirring without the vortex? If I buy a longer bar will that help, and if so, what is the biggest bar I can use with my plate (I remember seeing some stuff long ago about the bar length in relation to the spacing of the magnets...)?
Thanks!

 

[bucketnative]

Longer stir bar will result in a vortex.

In a lot of laboratory applications, a vortex is not recommended because it will introduce more oxygen into the solution.

In the case of the starter application, it is still stirring, and it is still introducing some oxygen (from the air) because it causes more water molecules to come to the surface. I'm not sure that you absolutely need a vortex for your starter. As long as it keeps the yeast in suspension.

 

[Remos112]

I'm not sure that you absolutely need a vortex for your starter. As long as it keeps the yeast in suspension.

I 2nd that, a vortex will likely add more oxygen, but as long as the yeast keeps in suspension you are making progress.

 

[gkeusch]

Thanks Folks! I hoped that was the case.

 

[Nebraskan]

Yep, you don't need/want a vortex. For doing 2 liter starters might I suggest something a little simpler?
I work at a winery where we make hundreds of thousands of gallons of wine and over 250,000 gallons of cider a year. We never use a 2L or such container to make up yeast. We use 5 gallon buckets, and used to use a SS spoon to stir in the yeast in the water, but now use a paint stirrer that we attach to a portable drill. It doesn't cost much and I think I found them at Walmart. These are the kinds that have the plastic cone at the bottom with fins.

Instead of messing with a flask and stir bar I would suggest a simple mason jar. Pint, quart or half gallon, depending on HOW much starter you are aiming for. Mix you yeast in these containers with the id and swirl them to get them hydrated or mixed well. If you are waiting for fermentation to develop, merely loosen the lid to allow gas to escape. It will double in numbers roughly in about 80 minutes, give or take, and will be a LOT easier than flasks and stir bars.

 

[The_Bishop]

This is wrong. For a starter, you are *trying* to introduce oxygen to the starter wort to enhance yeast propogation.

 

[Upthewazzu]

This is wrong. For a starter, you are *trying* to introduce oxygen to the starter wort to enhance yeast propogation.

This has always been my understanding.

 

[triethylborane]

This is wrong. For a starter, you are *trying* to introduce oxygen to the starter wort to enhance yeast propogation.

Yes, oxygen is critical to rapid and healthy yeast growth. O2 is used by yeast to generate cell membrane from fatty acids and steroid alcohols. Stir plates, frequent shaking, O2 injection, etc.

What @Nebraskan recommends is fine because of the scale necessary for the batch sizes. I disagree Vernon that a vortex in a fluid on a stir plate is not desirable, as that is an easy sign for people to determine that O2 exchange is occurring. Some here struggle enough with understanding that O2 is entering the fluid.

Do what is practical and what results in sanitary, healthy yeast.

 

[Ozarks Mountain Brewery]

if you cant create a vortex just open the container then close it and shake it up every now and again, you need the oxygen but you don't want it to ferment

 

[Nebraskan]

A very good read here: https://www.morebeer.com/articles/how_yeast_use_oxygen As for me, I like to see it fermenting at a starting level when I added it to the must/wine. I just started up a Munich Dunkel Sunday and early in the day prepared my starter and it was fermenting by the time I added it in about 7:00 pm. Monday morning it's going gang busters. It also gives you an indication that your yeast is not only viable, but very active and has reached a point of multiplication showing good live yeast.

 

[Pkrd]

If we want oxygen (and we do) why do we use those Erlenmeyer flasks with the lowest possible surface area? So we can pretend we're lab geeks?

 

[triethylborane]

If we want oxygen (and we do) why do we use those Erlenmeyer flasks with the lowest possible surface area? So we can pretend we're lab geeks?

Its all about that neck area and conical shoulders from the base, reduces spillage when mixing by hand vs a beaker, makes decanting easier vs a beaker, reduced neck area vs a beaker means less contaminants when properly covered.


With a stir plate and a loosely affixed square of foil to the neck of an erlenmeyer flask, plenty of gas exchange is occurring.

 

[Nebraskan]

Quart jar. Lid. Shake. little bird special... cheap, cheap, cheap.