Tonight I just made a stir plate from a CPU fan and the other good stuff. Once finished I was testing it out with just water in a 2l Erlenmeyer flask. I was just curious on what is the best size vortex for your starters. When at full speed the vortex reaches the bottom and violently sends bubbles everywhere. Is this harmful for the yeast? All the other starters I’ve ever done I’ve just swirled manually every now and again. Please let me know about how big you want the vortex and if its harmful for the yeast if it reaches the bottom hitting the stir bar.
All you need is a small vortex. This is enough action to keep the starter turning around and exposing more surface area to pick up oxygen. It’s not necessary to do more than that. Once the yeast has passed the growth stage (24-36 hrs), it is no longer necessary to stir (oxygenate) the beer as the yeast have consumed all that they need at that point.
thanks to you both!
I was just gonna ask the same question!
although I haven’t yet built mine… any thoughts about the need to make it more sturdy or adding extra components to make it last longer or do things in a more controlled way? I’m asking this because I’m seriously thinking about making mine as well and from watching youtube videos, I got various kind of homemade ones ranging from easy projects to more complex electronics!
so, is complex worth the effort and why?
thanks ahead!
I kinda figured that the small vortex would be more than efficient. I did however make 2 since a lot of times I will do 2 different beers on a brew day. The second one that I made I didn’t incorporate fan speed control so the vortex will hit the bottom and is really gets the water swirling fast. Just trying to make sure this isn’t harmful to the yeast in any way. I read a comment on another board about it being harmful but I take everything with a grain of salt and I figured I’d ask the question here because you guys have never steered me the wrong way.
If it isn’t too difficult, I would wire them both with speed control. Sounds like you have a much more powerful plate than the one I recently made. You definitely don’t want the vortex all the way down. If you are testing your flask with a full 2L are you able to turn down the speed to get a slower rotation and maybe a 1/2" vortex?
Just a dimple on the surface is sufficient. Don’t want to “sheer” the yeast membranes apart!
The vortex isn’t going to harm the yeast, they’re tougher than that. It is just not necessary.
A 1/4 inch dimple is all it takes for me. Don’t know about the shear on the yeast.
Where you been Hacker?
Workin’ my can off, mostly . . Also, over at the HBD, and getting started on the 8 Belgians for this year’s Tennessee Cigar and Brew Fest . . .
Thanks for asking! 
Woot! The answer to the question that I was actually asking, thanks Tom!
How do you guys cover the flask when using a stir plate?
just a piece of sanitized foil. if you boil the starter in the flask and put the foil on for the last few minutes of the boil that does it to.
I don’t even bother sanitizing the foil. I’ve found foil, plastic wrap, and paper towels to be sanitary right off the roll.
Paper towel or coffee filter w/ rubber band around neck.
Same here. Don’t know if it needs to be sanitized but a little squirt of StarSan is simple insurance so I always do that.
Not to hijak this thread, but I have a related question. When I first turn on my stirplate the vortex is 1/2 or so deep, but after 12 hrs there is often a layer of krausen on top. I am assuming that the stir-bar is not spinning fast enough and that allows the krausen to build up. Do others have the same experience?
The krausen is gonna build no matter the stir bar speed. Some yeasts will have more krausen than others . . particularly top croppers. I did twin starters of WY3787 last week and they climbed right out the top of the flasks. That’s why some folks use the anti-foam additive.
FWIW, I recently started using a starburst stir bar, which seems to create a greater vortex at lower RPMs.
What’s a starburst stir bar and where did you get it?
I have had problems with my stir bar being thrown off even at the slowest speeds. Do you think this would help?