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Making a Stir Plate As a Home Brewing Aid

Updated on August 24, 2017
Frost Birch profile image

A person of many hobbies and interests ranging from Dungeon & Dragons, electronics, map making, my dog. camping and now Cider making.

Making Homebrew Equipment on the Cheap

I found a new hobby today. As usual, I jump in with both feet and have to have everything. So I do some extensive research online through YouTube video tutorials and hobby forums as well as home brewing stores websites to see what is out there and what is needed to start the hobby.

One of the pieces of equipment that caught my eye is used as an aid for propagating yeast. A device used to automatically stir a yeast culture so as to introduce oxygen. Oxygen aids in yeast production, cutting down the wait times in brewing. That leads to faster alcohol production and a quicker end product which is the whole reason for the process.

Let's make a stir plate.


Parts List

  1. 140 x140 mm computer case fans with speed control. ~ $14.95
  2. 12vdc power supply ~ $5 at second-hand store
  3. Plastic cheese cutting board ~ $2 at a dollar store
  4. 2 1/2 in machine screws and hardware.
  5. 2 neodymium magnets (rare earth magnets) - scrounged from an old hard-drive or bought for a few dollars at a hardware store.
  6. epoxy glue


  1. screw driver and wrench
  2. glue gun
  3. electrical tape
  4. soldering iron (optional)
  5. shrink tubing (optional)

In my bio, if you read it, it states I am interested in electronics so this is another reason I picked this project as my first one. My interests intersect. I dug through my box of old computer parts and came up with an old computer 140mm case fan with a 3 position speed switch, and 12 VDC power supply, some rubber case legs and some nuts bolts and washers.

I had to look around for some rigid plastic for a work surface. I found one in a small cheese cutting board. It fits the fan housing perfectly and even has a handle so the rig can be stored on a hook when not in use. I'll have to head to the dollar store and pick up a new replacement before my wife finds out.

Starter flask and stopper.

1000ml Narrow Mouth Erlenmeyer Flask with Rubber Stopper, Karter Scientific 213G22
1000ml Narrow Mouth Erlenmeyer Flask with Rubber Stopper, Karter Scientific 213G22

There are several reasons to buy an Erlenmeyer flask; the most important one being the cool factor. It just makes your brewing area look like a scientific lab. The other reasons are its shape makes it difficult to knock over and spill the contents. The wide flat bottom lends well to using the stir plate. The graduations on the side of the flask make measuring easier.

Buy a flask at least 1000 ml. Any smaller and you'll find the yeast starter will just over flow the flask before you get enough to use. The larger the better for making a yeast starter. I use a 2000 ml flask because it is easier to handle and clean.

Do not be tempted to use the stopper when proofing yeast or you'll end up making a grenade, or at least a large mess to clean up. Make a foam stopper or just cover the flask mouth with some sterile tin foil when using the stir plate.


Magnetic Stir Bar

SEOH Magnetic Stir Bar Plain PTFE 6 x 25mm Pack of 6
SEOH Magnetic Stir Bar Plain PTFE 6 x 25mm Pack of 6

This is an important part of the system. You can get away with an old jar or bottle with a flat bottom instead of an Erlenmeyer flask but you need to have the magnetic stir bar for the system to work correctly. Get the stir bar that doesn't have the center ridge. They are quieter when used in a glass container.

They also come in several different sizes and shapes. I suggest a one-inch (or 25 mm) long stir bar as a minimum for this project. You can get different shapes but then you'd have to alter the positions of the magnets on the fan to match those of the stir bar.

The PTFE coating makes it easier to sanitize before and after use. It also makes it quieter and spin more freely.


Using the Stir Plate

I use the stir plate for making a yeast starter for my cider and beer production. When using dry yeast, you can bloom the yeast in a flask a day ahead of your cider making for a couple of reasons:

  • to test the viability of the yeast.
  • to increase the amount and vigor of the yeast colony.

Adding a large colony of yeast to your brew will ensure the yeast overpowers and wild yeast in the mix and give you better, faster results

  • Once your brew is finished you can reuse the yeast left in the bottom of your brew container. Use fresh yeast nutrient and increase the volume of viable yeast so you can separate the old spent yeast by alternately growing, settling and pouring off the viable yeast and throwing out the spent yeast. Going through a few cycles will leave you with clean viable yeast for your next batch of home brew.

American Educational Bomex Glass Conical Separatory Funnel, 1000mL Capacity
American Educational Bomex Glass Conical Separatory Funnel, 1000mL Capacity

If you are really into reclaiming your yeast colony to reuse from brew to brew then using a separation funnel will make the task so much easier and faster.

Using a separation funnel allows one to clean the yeast faster by separation out the spent yeast through the bottom port.

One caution with this funnel. There are some that have a metal spring clip to tension the stopcock at the bottom. be aware that some of the brewing sanitizers are acidic and will react with the metal.


You can use the stir plate for other things.... my wife uses it to clean her jewelry.

© 2017 Frost Birch


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