Fermentivity: Equipment: Homemade Stir Plate

Saturday, April 20, 2013

Equipment: Homemade Stir Plate

In addition to temperature control (a future blog post), one of the best ways to improve your homebrew is by pitching adequate amounts of healthy yeast. Depending on the OG of the wort you are trying to ferment, one vial or smack pack of yeast may not be enough. I recommend using a yeast calculator, such as one of the calculators in the links list, to estimate how much yeast to pitch. But how do you pitch enough yeast without wasting money on multiple vials or smack packs? Use a stir plate. A stir plate allows one to grow up a large amount of yeast quickly via continuous aeration of the yeast starter wort. Stir plates can be purchased from many vendors, but they are easy enough to make yourself with a few key items and some knowledge. Here's how I made mine.

The stir plate is, essentially a spinning magnet that turns a magnetic stir bar inside your flask or beaker containing the yeast starter, so you need something that spins: a computer fan. You also need some neodymium magnets. These are easily purchased, but can also be found inside computer hard drives. These magnets are then hot glued to the center of the fan. You'll have to experiment with this to get the best placement. I used a piece of plexi-glass as a mounting surface, but there are many possible applications (a lot of people use cigar boxes or plastic project boxes). Needed as well are a 12V AC power converter and a potentiometer/rheostat (available at Radio Shack). I also added an on/off toggle switch.

I will warn you that some easy electrical wiring is necessary for this project and that if you don't have confidence in what you are doing, don't do this project. You could get hurt, or worse. Disclaimers aside, I wired mine very simply with electrical tape, although soldered connections are recommended. Here is a wiring diagram, but there are several examples available on the internet.