Bart's Fantastic Presentation on Yeast Starters


What is a yeast starter? A yeast starter is essentially a mini batch of beer. It is made to give your yeast a hospitable environment suitable for them to reproduce making millions if not billions of yeast babies that will eventually help ferment your beer.

Benefits of Making a Yeast Starter

  • A package of liquid yeast typically contains 100 billion yeast cells. A starter will allow the yeast to multiply so you can pitch the correct amount of yeast for your beer.
  • Saves you money. You don't need to buy more than one package of yeast.
  • As yeast ages, it becomes less viable. A yeast starter will bring it back up to strength.
  • Helps speed up lag time. Your wort will start to ferment faster.
  • Under pitching will stress yeast. This can cause phenolic and ester flavors in your beer.  Prevent this by pitching the proper number of yeast cells.

Materials Required

  • Erlenmeyer Flask (sized appropriatly for your starter size)
  • Stir bar
  • Pot
  • Funnel
  • Calculation tool (Beer Smith, Mr. Malty, etc...)
  • Yeast
  • Light Dry Malt Extract (DME)
  • H2O
  • Tin Foil
  • Stir Plate (optional, but recommended)
  • Thermometer
  • Sanitizer (Star San)

 How to Make a Basic Yeast Starter

  1. Start the start the day before you brew. Try to allow 24 hours for the yeast to multiply.
  2. Use your calculation program of choice to determine the required amount of H2O and DME required.
  3. Mix the H2O and DME, then bring to a boil for 10 minutes.
    • NOTE: As the work starts to boil it will foam up quickly.  Remove from heat and stir to prevent a boilover.  Return to heat and continue until the hot break passes.
  4. Sanitize your flask, stir bar and funnel.
  5. Place stir bar in the flask.
  6. Add the boiled mixture (wort) to the flask using the funnel.
  7. In an ice bath, chill the flask and wort to room temperature.
  8. Add the yeast to the flask.
    • NOTE: Make sure you have done the previous step and chilled your wort first!  If you pitch your yeast in boiling work you will KILL your yeast!
  9. Sanitize some tin foil and use it to loosly cover the flask.
  10. Place on the stir plate and allow to spin for 24 hours.
  11. Decant the foam off the top of the flask after 24 hours
    1. Allow flast to sit (at room temperature) without stirring for 2 hours.
    2. Yeast will settle out of suspension and you can pour the excess wort off. This liquid is not tasty. You don't want it in your beer!

Benefits of Stir Plates

  • They are cool looking and make little home tornadoes.YeastStarter
  • They increase O2 and decrease CO2. "Burp and Breathe"
  • You increase cell count with increased oxygen.
    • Yeast can be both anaerobic and aerobic
    • When anaerobic (NOT in the presence of O2) fermentation occurs.
    • When aerobic (IN the presence of O2) yeast reproduce like rabbits.
  • The stir plate produces a perfect environment to allow your yeast to breathe and reproduce. This is also why tin foil is used, and not a rubber stopper. The flask must not be airtight.


  • Yeast starters are a fast and easy way to increase your yeast cell count.
  • Many brewers think this improves the fermentation process and overall outcome of their brews.
  • Very few steps and supplies are required.
  • Stir plates aid in the starter process by introducing plenty of O2 for maximum reproduction.

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