Stir Plates Information

Most home brewers believe that increasing yeast volume is the primary reason for growing a yeast starter. Although your yeast volume will increase dramatically, the primary reason for growing a starter is so that you can pitch actively growing yeast into your wort. And when you do it right, the yeast from the starter literally explodes through your beer and your air lock will be bubbling in less than an hour. The advantages of using a starter:

  • You are pitching a known, viable yeast culture
  • No anxiously waiting for up to 3 days for your yeast to “take off”
  • Because the yeast takes off immediately, there is less chance of infecting your wort and less chance of producing a bad batch of beer
  • You produce a cleaner, high quality beer
  • Lagers finish up to one week sooner, ales finish up to three days sooner

But what does this do for me? It’s simple. Your wort starts fermenting much sooner and much faster. The immediate result is that the few “bad bugs” that always end up in your wort never get a chance to take off and spoil your beer. And because your wort starts faster, it also finishes faster, up to one week sooner with lagers and up to 3 days sooner with ales. In other words, the quality of your homebrew beer can be dramatically improved by making a yeast starter.

To make your own starter: 

Ideally, your stirplate starter should be started 2 - 3 days before brew day. Remember, you are after a lot of activity, not necessarily maximum volume. We are not saying that extra volume is a bad thing but if you had to choose between the two, actively growing yeast will do your beer more good than more yeast that is already going to sleep. Measure the right amount of DME (Dry Malt Extract) or LME (Liquid Malt Extract) for your starter. For dry, this would be about 3 ounces by weight per 1000 ML. For liquid, this would be ½ cup per 1000 ML.

Starter Size DME (Dry Malt Extract) LME (Liquid Malt Extract)
250 ML 1 Ounce 1/8 Cup
500 ML 1.5 Ounce 1/4 Cup
1000 ML 3 Ounce 1/2 Cup
2000 ML 6 Ounce 1 Cup
1 Gallon 12 Ounce 2 Cup

Note: Some brewers will add hops to their starter or will try & match their beer’s starting gravity. Neither is necessary. You are making a starter, not a beer! Pour the extract into your flask, add water, drop in a stir bar and cook at a low boil for at least 10 minutes, pull the flask off the heat and immediately cover the opening with a piece of aluminum foil & let cool to room temperature.

Note: We recommend a flask made of borosilicate glass because borosilicate glass can withstand direct heat. If you are using a glass jar or a flask not made of borosilicate then you will need to sanitize the flask with a product like StarSan, cook the extract in a pan and then pour it into the flask after it has cooled to touch.

Place starter on the stir plate with the foil cover still in place and swirl at high speed for at least 10 minutes. This will pull oxygen into the starter. Slow the stirplate down until the vortex in the middle is less than ½” tall, pitch the yeast & immediately re-cover with the foil. Let spin until you are ready to pitch the yeast into your wort.

Note: Some brewers will use an air lock. You really don't need one because the yeast will be actively producing CO2 the entire time it's in the flask and the positive pressure inside the flask plus the foil cover will keep any bad bugs out. If you are using a jar instead of a flask, just screw the lid on very loose. Screwing the lid on tight will cause an explosion!

On brew day, brew your beer as normal then pour the starter into the wort once it has cooled enough. Note: Some homebrewers pour off the liquid and only add the yeast that has settled to the bottom. But it's best to swirl the flask and than pour the entire starter in the wort, liquid and all. Although it's not obvious, there are millions of yeast cells floating around in the liquid. Don’t forget to hold the second stir bar against the bottom of the flask to keep the magnet inside while pouring out the starter, otherwise you will be fishing it out of your fermenter later!

What about starting White Labs yeast? An average White Labs yeast vial contains around 100 billion cells of active yeast. And no matter what anyone else may tell you, there are more than enough yeast cells in a vial of White Labs yeast for a 5 or 10 gallon batch. Why? Because soon after you pitch a White Labs yeast vial, the yeast multiplies into a much greater yeast volume. Most who make the “would need two yeast vials for a 5 gallon batch” statement fail to mention this. The issue with White Labs yeast is that it can sometimes take 2 – 3 days for a yeast culture to take off.

During this wait, you are anxiously watching and hoping that things don’t go south. A starter solves this problem by pitching actively growing yeast into your beer. Another neat trick is to use a stir plate to stretch a vial of White Labs yeast. You can pitch ½ a vial this time, close the vial & put it in the fridge. Then you can use your stirplate to stretch the second ½ of the vial for another batch of beer.

What about Wyeast? Wyeast solves the startup problem that White Labs has with their smack packs but they have the opposite problem – relatively low pitching volume. There is not near the volume of yeast in a Wyeast smack pack. Also, Wyeast smack packs have been known to not blow up as they should, leaving you with a pack of stressed and underperforming yeast to pitch into your beer. You can use a stirplate starter to solve both of these issues. Just start the smack pack two days sooner and pitch the contents into your starter flask 2 days before brew day. Then you use the stir plate to grow an acceptable active yeast volume for your brew.

What about dry yeast packets? Most homebrewers still use dry yeast because you can’t beat the convenience or cost. Also, you will rarely get a bad pack of dry yeast. Some believe that dry yeast starts faster than White Labs yeast. But they don’t understand that the initial Krausen they see on top of the beer is not the result of fermentation. The foam is cause by the yeast cells hydrating or taking on water.

Dry yeast can easily take as long as White Labs yeast to start. Dry yeast starters are done by just sprinkling the yeast into the vial just as you would the other two. And the benefits of using a starter made from dry yeast are the same as the others.

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