Yeast stir-plate build

You can tell when this home-brewing has stopped being just a hobby and become a weird obsession; it starts with a bit of canned kit brewing, then you go to extract and before you know it you’re doing all-grain.  Then you start building temperature controllers, brew-fridges and all manner of other shite that clutters up your house.  For my money, the ultimate “you’ve getting into this too deep” accessory is the yeast stir-plate.

Eh?  Whassat?

A stir-plate is just a way of keeping a yeast starter in constant motion and adding in a steady supply of oxygen – so that when you come to pitch the yeast starter into the wort, your yeasty mates are in perfect condition.

People who ferment their beer from yeast starters report better attentuation in their fermentation, improved taste in the finished beer and increased virility in the bedroom.

I’m also hoping that it’ll mean that I can culture up yeasts from bottles of commercial beer that I’ve particularly enjoyed (Hook Norton, Adnams and crazy Belgian beers especially)

There are already tons of posts and articles on other blogs detailing how they made their stir plates and why they make starters, etc.  So I’m going to just include the information here that I found useful and had to hunt around for, plus some pictures of my incredibly shoddy workmanship (it’s no surprise that I work in IT and am not a craftsman or tradesman)

20150122_201031It’s basically a lunchbox, with a computer fan, some neodymium (rare earth) magnets, a rheostat and an old phone transformer.

Here’s the parts list and where they came from:

  • Lunchbox from the cheapskates shop (£1.39)
  • 5v Phone Charger (Free from the parts bin at work)
  • 12v PC case fan (1x bottle of homebrew to the guys in desktop support at work)
  • 50x 10mm x 1mm rare earth magnets ( £3 or so from fleabay, I used six of them)
  • 1x 25ohm 3Watt Rheostat (£4 fleabay)
  • Electrical tape and Blu-tack
  • Some m4 long shank bolts and nuts to secure the fan to the lid of the lunchbox

As you can see I’ve very professionally attached the magnets to the fan hub using Blu-Tack.  It’s the only thing that worked.  “No more nails” was a dead loss.  Araldite would probably have worked:

20150122_202738

I wired the positive in to the central pole of the rheostat and the positive from the fan to the left pole.  This seemed to work OK.  I also had to use a 5v power supply as a 12v caused the fan to skitter around the room whenever powered on (with or without the rhesostat):

20150122_202803

Once we were all assembled I only had to put the Borosilicate 1L flask on top (£9 fleabay again) and drop in the smallish magnetic PTFE-covered stir-bar from the set I bought (7 pc set £9 fleabay)

With the rheostat set to about halfway you get a nice little whirlpool – which should be enough to get a starter going:

20150122_203759

..and if you really crank it up, you get a right old vortex!:

20150122_203210

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