I want to re-suspend yeast and generally keep a brew uniformly mixed in a carboy without having to open it and expose it to oxygen every time. Is there a hobbist-priced magnetic stirrer that works for this kind of application? Right now, I'm thinking about the long-term aging process of a red wine.

In a quick test I found that the dome of the carboy makes it a little hard for the stirrer. Most chemistry mixing flasks have flat bottoms it seems for this reason. The magnetic field from the external mixing plate is also weaker at the top of the dome (farther away). I'm fine if one side of the carboy is mixed more than others.

1 Answer 1


Yes you can. I've fermented apple wine this way on a DIY stirplate, 1 inch magnet, and a vintage arrowhead carboy (flat bottom).

It wasn't powerful enough to make a deep cone for oxygenating which actually worked nice as I just wanted to deny the yeast the option to flocculate.

My stirplate uses an old SCSI external 5.25 tape drive, so it's platform is about 12x12inches. With a 6 inch fan for the magnet.

Edit: I've seen a stir plate successfully used on stainless 15.5g keg. It was used with a herms system for kettle souring. Many do use these kegs as fermentors too. Maybe an option?

  • have you ever tried with a dome-bottomed carboy? i want to order a larger stirring magnet but am not sure how large or what form factor to go.
    – tarabyte
    Nov 29, 2017 at 0:22
  • @tarabyte mine doesn't work with my new Italian glass carboys (domed) the distance is too far for the magnetic field, also it's impossible for me to center it on the dome crown when it does grab it flips of even when dry testing. Bar wobbles horizontally. Nov 29, 2017 at 12:13
  • 1
    I have a stainless fermenter with a flat-bottom. Generally stainless steel is non-magnetic, so theoretically this should work too.
    – Kingsley
    Feb 18, 2018 at 0:05

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