Hello fellow brewers,
I’ve been brewing with starters with great results for quite a few batches, and I recently purchased a new stir plate and I have two questions.
When I dial in the speed, how far down the flask should the vortex drop?
I know the little yeasties will multiply a lot faster, about how long do you think it should take to be ready to pitch now that I’m using the plate?
All you really want is a 1/4-1/2 inch dimple. Otherwise you have a much higher chance of throwing the stir bar. Any faster than this won;t do you any more good, just keep the yeast suspended and you will have great results!
For me, I set it to the lowest speed that prevents any of the yeast from floculating. I don’t think it’s necessary
or beneficial to circulate any faster than keeping all of the yeast in suspension.
If you see a dimple, that is plenty. Anywhere around in that range should be fine. In the big picture, it isn’t really critical as long as you keep the yeast well distributed and the CO2 driven off.
As for how long you need to wait until you are ready, I’m sure it is faster, but I can’t be more specific. But you may want to consider letting it ferment all the way, cold crashing, decanting the ‘beer’, and pitching the yeast slurry. That’s the best way, IMO, to make sure the yeast has used the oxygen to build strong healthy cell walls and that you don’t get any off flavors from the starter ‘beer’.
I’ll usually start with the lowest setting and gradually increase the speed over the next day or so as the starter thickens with the yeast slurry. After a day or two, you’ll be pretty much ready to go. You should instantly recognize the color change to the starter as the yeast reach population. You can chill and decant after that if you want to.
All of the growth should be done within 36 hours.
Who’s the new guy?! 
Just got to this post from a link NorthernIke put in a reply to himself about the same topic.
Is aeration a factor in doing a starter? I would imagine it is in order to have a nice healthy batch of yeast that’ll propagate well once you pitch it. I’ve always tried to get the crazy vortext (to use NorthernIke’s words) in order to make sure I have sufficient oxygen in the wort. Is a small dimple sufficient for oxygenation?
I may be double tapping it, but I give a good shake to the flask before adding the yeast. I can’t speak all scientifical-like about the amount of oxygenation it provides, but my starters have always been happy, healthy, and successful using this method.
Yep.