stir plate question

[Waldo]

I built a stir plate but I can only get the stir bar to to spin on less than full power. My question is, is it important to have a vortex, or that the wort spin and circulate? Thanks - Bill W.

[spiderwrangler]

All you need is some movement, that will be enough to get turnover in the top layer of your starter, which will allow for ready gas exchange. A vortex is not at all needed. Have fun with your new toy!

[BDawg]

Are you testing this with wort or with water?
The gravity makes a huge difference.

But you only need it to stir. You don't need a tornado.

[spiderwrangler]

Good point Bdawg... as long as your wort is moving you are good.

[Waldo]

I tested it with water the other day and I got a good vortex at 3/4 speed...Now I am using wort and it is moving nicely but no vortex. Am I supposed to get a lot of krausen with this. I can see that there is more yeast because the wort is a lighter color than it was before, but no heavy krausen. There is foam just not a huge amount. I also noticed that at full speed the magnet spins off center and I have to stop the plate and start it over again. I think part of the problem is the growler I am using has a curved bottom. I will have to get an Erlenmeyer flask at the LHBS when I go next

[captain carrot]

The Erlenmeyer flask will bring the stir bar closer to the magnet also. I agree the curved bottom of the growler is probably most of your problem. Good luck!

[spiderwrangler]

It's simply not necessary to have a raging vortex. You are trying to get turnover in the wort to allow for gas exchange and keep the yeast up in suspension, not make them feel like they are in a tornado. I'm assuming you have foil over the top or a foam stopper rather than an airlock?

[BDawg]

Don't expect a lot of foam with a stir plate.
(Though I got a blowoff one time stepping up a smack pack of 3068 -- but that's unusual).

Also, the shape of the bottom of your vessel determines the kind of stir bar you need to use:

Flat or convex bottom (ie, curved where the stir bar sits "on the top of the hill") use either a straight bar, a tapered bar, or with a single center pivot ring.
concave bottom (the stir bar sits at the "bottom of the hill" - it's best to use a barbell type which has 2 pivot rings, one on each end.

(If you don't know what a pivot ring is -- think of a tiny cock ring ).

HTH-