I lost my old stir plate, so made up a new one with a spare LM311 that I had laying around the place.
The intention was to put on 40l of an imperial stout, so I went through the calculations and it reckoned I needed 430bn cells. I was starting with 1bn cells of American Ale 1272, and the recipe called for a 4l starter.
My Erlenmeyer flask was 1l. So I got a plastic bread-making bowl, filled it with water, spinner worked, so I threw in some DME, topped it up with water, and let it cool. Pitched yeast, set it up in the hot press (the rest of the house is usually around 14C this time of year) and turned on the stirplate. All I got was whirring, rattling. Fucked if I could get it working. I must have spent hours fiddling with positioning, speed etc. Couldn't work it out. There must have been something wrong with the bowl interacting with the magnet.
Anyway. The yeast starter mostly worked, I got a decent harvest, so I threw it into the fridge with my IPA I was getting ready to keg, and left it until tonight, where I was going to top it up for a brew tomorrow...but there is an acetobacter tang off it :( probably because I couldn't leave the thing alone for the first day...and it couldn't get enough aeration, so it produced alcohol. Dammit.
So. I assume bowls don't work for stirplates. Assuming I actually do need a 4l starter, how the hell can I make one, without blowing €100 on a giant flask on ebay ? I'd also really like to get this imperial on.
Stir bar could be too big or too small?
Maybe. How do you size them ?
Was the bread bowl coloured or clear?
Erlenmeyer allows you to see the stir bar to line it up.
The thickness of the plastic could be a factor.
Unrelated but glass is more sanitary than plastic.
I decided to science the shit out of it. Got a whirlpool going in the flask with water, then with dme. You definitely need more juice, one you add sugar.
Moved over to the 4l bowl. Again, I needed more juice. I think the rattling wasn't "Going to fast" but actually "Too slow". And when things go wrong for you, obviously you go conservative. Bah.
Anyway, got a lovely whirlpool going, with 4l of wort. Just needed to spin the medium-large magnet a little faster than I expected. Though, every few minutes I can hear it going off the rails. Instinct tells me that it's a chaotic system and will go out of kilter at some point, so I just need to fine-tune the speed settings a little. Yay for going with a variable pot into the LM317 AND the three-speed-selector on the fan :)
Just need more yeast now. Dammit. €13 and a week of waiting.
For a 4L Erlenmeyer substitute just use a demi-john!
Ok its not Pyrex but a decent stirrbarr should work in it. If not just shake it around every now and again.
Its not recommended to run the stirrer 24/7.
Why not run it 24/7?
Make up 1l, stir gently 12hours 18-20 degrees
Settle, Pour off and feed again, repeat and you will have enough.
What was your bowl covered with?
How did you sanitise it?
Most bowls unlike erlenmeyers are concave and it's too close or too far a gap between magnet and stir plate to work effectively.
If it's too close use cardboard spacers
Remember with stirplates not to whip the shit out of it just keep yeast in suspension.
You could use a sanitised 5l water bottle with lid just barely screwed on, give it a shake every time you pass it will take 24 hours longer than stir plate but works well