Well, perhaps throwing your stir-plate away is a bit drastic. Recycle it in an earth friendly manner. No, keep it – you might still need it someday.

Personally, I’m pretty much done with mine. Actually, it’s my second stir-plate. The first, a modified computer fan, burned out. I had high hopes for the second one. It was pricey. It had a Pulse Width Modulated (PWM) speed controller. It had a catchy name. So why didn’t I like it?

One of my issues was the magnetic stir bar – is it rotating or off to the side flailing around? The starter is opaque, so you can’t see the bottom. Did it start up too fast and get thrown to the side? Shouldn’t there be a vortex? How much heat is the stir plate adding? These issues bugged me.

The next drawback is the 2L Erlenmeyer Flask. If you boil wort in it, you’re bound to have a nasty boil over – Fermcap S does help with this. I’ve also scorched my starter wort many times. Black flecks in the foam. Burnt odor and taste. To resolve this issue, I started boiling water in the flask to sterilize it, and boiling the starter wort in a separate 12qt kettle. Boil over solved, scorched wort problem – solved. There is a low level chance of contamination or hot side aeration while pouring the wort into the flask depending on whether you transfer hot or cold.

I was not very happy with the stir plate in general.

The final straw was when I found large clumps of yeast all over my kitchen counter. I was experimenting with a technique I had seen at a brew club meeting – using an aquarium air pump with a .5 micron stone in the flask on the stir plate. I turned on the pump and the stir plate and went to bed. In the morning, it was a huge mess and a huge waste of apparently healthy and happy yeast. Happy at least until they dove to their death on my counter top – like a bunch of Lemmings running off a cliff. It was time to take corrective action! It was time to find a replacement for the stir plate.

For whatever reason – eventually you will want to make a big starter, perhaps for a strong ale or a lager. My next smallest container at home is a 3 gallon carboy that I bought for making large “simple” starters. A simple starter is one that you try to remember to intermittently shake or swirl when you happen to walk by. You can make it less simple by squirting it with O2 or by adding an air pump and an aeration stone. These aren’t satisfying solutions – the rule that “a bad starter is worse than no starter” comes to mind frequently. Relaxing, not worrying, is very difficult without some amount of Zen training in the art of yeast propagation.

The Wyeast website provides this information “it is very important to increase your pitch rates according to the original gravity of your beer. A good rule to follow is a million cells per milliliter per degree plato.” And “Anytime you are pitching yeast into a harsh environment (high gravity, low temp) you need to add additional yeast. A rough rule of thumb is to double pitch rates above 1.065 and triple pitch rates above 1.085.”

The White Labs website provides similar advice. “While a starter is not always necessary, White Labs recommends making a starter if the Original Gravity is over 1.060, if the yeast is past its “Best Before” date, if you are pitching lager yeast at temperatures below 65°F, or if a faster start is desired.”

I’m a huge fan of the Jamil Zainasheff’s Mr. Malty® Yeast Pitching Rate Calculator™ and related podcasts. From the site, using a stir plate and a 2L starter, you can brew up to a 1.0856 OG beer. This is much stronger than what I usually make, but not always! I do make the occasional Barley Wine or Old Ale. These would exceed my 2L stir plate limit. I also tend to make the occasional lager over the 1.042 range, again exceeding my 2L stir plate capacity.

My initial thought for a stir plate replacement was to make an orbital shaker – like you find at your local hardware store for mixing paint, but a much gentler rocking motion. I think I saw one on the Discovery Channels “Brew Masters.”

While doing my typical research (I have OCD tendencies), I also found an article on the White Labs Inc. website. “The White Labs propagator with Frings aeration technology offers reduced propagation time, high cell density and dissolved oxygen contact.” This is a rotor-stator turbine system. Both of these systems, the shaker and stator, are beyond my ability to fabricate at home. They obviously have merit and I look forward to ambitious home brewers experimenting with them and submitting write ups!

I settled on a “Lab Mixer” design. This design involves a variable speed motor, a shaft and propeller and a sturdy base with vertical and horizontal adjustments. Apparently they are quite common in commercial environments, but I haven’t personally seen them in use in a home brew setting! Google Cole Parmer Lab Mixer for samples.

The main components of the system are the motor and speed controller.

Radio Shack Project Box $4.99
Grainger Control, DC Speed 5JJ56 $68.60
Coupling, Rigid Steel $6.69
Motor, 90VDC, TENV – 3XE22 $131.55

The motor selection took me quite a bit of time. I wasn’t sure what speed to run a lab mixer at with a yeast starter. I bought and tried 93 RPM gear motor (Grainger Item 1LPW5). It was too slow to be effective.

The 3XE22 is rated for continuous duty, totally enclosed, not ventilated, permanent magnet DC motor with a 5/16” shaft diameter. Please note that motor manufacturers consider 8 hours continuous duty. Also, these are not brushless motors – brush and commutator maintenance will be required over time.

3XE22 90VDC Motor

3XE22 90VDC Motor



Model RPM Torque IN/LBS HP F/L Amps Volts DC L1 L2 C
3XE22 1800 1.3 1/27 0.46 90 4.68 4.93 6.43

The speed controller is a Dart 15DV1A controller, which handles 120V input and provides 90VDC output. It has a 25:1 speed rating, 1/50 to 1/3 HP, 2 Amps maximum current.

Variable DC Speed Control 5JJ53

Variable DC Speed Control 5JJ53

Now that I had the motor and speed controller selected, it was time to get a shaft for the mixer. A cheap fiber-glass rod from Home Depot fit the bill (orange drive way marker). When cutting the rod to size make sure you watch out for splinters! Next, I drilled a small hole in near the bottom. Two lock ties form the “propeller”. I actually tried multiple rods and shafts and this is the best arrangement I could find for this application.

The “base” was a challenge to piece together. If you have a friend that can do some tack welding, you can save a lot of money. My base is made from square perforated steel bars, bolted together with 8” corner braces. The 1” x 3’ and 1- ¼” x 3’ (cut) perforated steel bars give me vertical and horizontal telescoping ability. I added adjustable feet and rubber stoppers to guard the sharp edges. All told, the stand was half the price of the entire project. It is sturdy and multipurpose though – so if I want to use the system as a mash mixer or to whirl pool the wort in the kettle, I can (and have already done so!)


Looking at the pictures below, I’m using a 3 gallon glass carboy to mix a 2L starter. Note the air pump – this is in place to create a positive air pressure inside the container (keeps the airborne bugs out). A starter of 3L or 4L is well within the capacity. I may move to a 5L Erlenmeyer flask so it can be sterilized lacking the ability to autoclave my 3G glass carboy. A friend notes that he has broken two of the 5L flasks, so care is required when handling them. He also points out that sterilizing the carboy should be sufficient, which is confirmed on the MrMalty.com website.

After the research, cost and work – I’m convinced that buying multiple packets or tubes of Yeast is probably the best bet for most home brewers. You can buy a lot of pitches for the cost of stir plates, flasks, oxygen, aeration stones, air pumps and in my case – building a lab mixer. My joy comes from solving challenges, so the project was rewarding. Watching my yeast start off with short lag times and finish quickly with high attenuation rates is also a great reward for me – and for the consumers of my beer!

The lab mixer with a 2.0 L starter. The air pump keeps a positive air pressure inside the container so that air is flowing out, instead of in.

Lab Mixer In Action

Lab Mixer in Action

The base. If you can tack weld, you can save a lot of money on nuts, bolts and corner braces.


Base Bolted together with Corner Braces

Base Bolted together with Corner Braces

The lock ties actually provide plenty of impulse for stirring.


Lock Ties and Fiber Glass Rod

Lock Ties and Fiber Glass Rod

Sample calculations for a 1.066 OG.

1000 mL = 1 L, 1 gallon = 3785.412 milliliters, 5 gallons = 18927.06 milliliters = 18.92706 L

1 Billion = 1000 Million. 1 Million = 10^6 = 1,000,000.

1.066 OG = approximately 16.06 Plato

1 M Cells / mL / ° Plato * 18927.06 mL / 16.06 ° Plato = 305,140,000,000 = 305 Billion

1 liter starter = about 150 billion cells

2 liter starter = about 200 billion cells

1 tube or pouch (100 billion) pitched into 4 liter starter = 400 billion cells


Please note that White Labs warns against starters over 400 billion cells for a 5 G batch – “more cells are not detrimental until about 400 billion cells.” They also note that “One thing that contributes to flavor contribution in beer is yeast growth. If less yeast is pitched into beer, more yeast growth takes place, so more flavor compounds such as esters are produced.”

Jamil uses the George Fix values 0.75 billion cells for each point of gravity for an ale and 1.5 billion for a lager, so these simple calculations won’t match what you see on MrMalty.com.