Stir Plate Vortex Question

[fishslayer]

Just built my stir plate and can really only get a small dimple on the surface. Maybe 3/4 of an inch before it kicks the bar. i am using a 1.5 inch bar and am going to buy and try a smaller bar, but how much of a vortex is really needed?

Brian

 

[maffewl]

A dimple is all you need. As long as its stirring, you're in business.

 

[kh54s10]

I agree. Just a constant stirring. Enough to move all the starter wort, no need for a great maelstrom.

 

[Gavin C]

You can see how well it is stirring by having it fun with water and drop a little something in. Oxiclean is good as you can se the particles flying around and dissolving.

Just did this with my new 5l flask to assess the stir. Even on the slowest possible speed there was good mixing/agitation going on.

In summary. Not much in the way of a dimple is needed. The yeast will be kept in suspension and exposed to the constantly aerated wort.

 

[fishslayer]

That's what I thought as well. This forum is the best on the net for reality checks. I have a bio background and was like hmmmm let me ask the forums. Thanks guys!

 

[agentgreen]

I built my stir plate yesterday and I will say that I'd throw the bar all the time until I really centered the magnet on the fan. It took about 20 mins of "move magnet.... Look down to see where stir bar sits on the magnet.... Turn fan on... Bar thrown.... Repeat" until I got the magnet centered correctly and the bar wouldn't be thrown at any speed... Just something else you may want to check.

 

[Oginme]

Really the purpose of the stir plate is two-fold. (1) is to keep the yeast in suspension rather than allowing it to settle and pack on the bottom. This allows for better contact of the yeast cells with the nutrients in the wort. (2) is to promote oxygen exchange into the wort which the yeast cells need to create sterols to help build healthy cell walls as they multiply.

So as long as you have enough agitation to keep the yeast cells from settling and enough flow to bring oxygen poor wort to the surface you will be in fine shape. A small dimple on the surface is enough evidence of that.

 

[stevestrem]

Huge thank you to agentgreen. I built a stir plate a couple of months ago and was seriously frustrated by the bar being constantly thrown off the magnet. Kind of gave up on the damn thing.

Read the post about centering the magnet and now the stir plate couldn't be working better. Ran a test last night with water in a flask and it ran all night with no bar throwing.

First brew with the new stir plate on Saturday.

 

[Gavin C]

Adding to my earlier post in this thread. I recently read some of the Braukaiser's research on stirring speeds and it seems more is better. I added two of these magnets lenghtwise to my stir plate and can no go full speed ahead without the bar getting thrown. 2L or 5L no problems.

Edit: It ends up as a 2 inch long magnet spinning.

 

[trentm]

http://braukaiser.com/blog/blog/2013/03/25/stir-speed-and-yeast-growth/

~40% more yeast when stirring at high speed compared to dimple speed! 100 Billion more cells in a 1 liter starter! No brainer!