Making a Yeast Starter

When I was beginning to brew, the only available yeast packets came from companies that did not supply enough yeast in one vial for a full 5 gallon batch. Because of this I tended to use only dry yeast packs. These typically contain enough yeast for a standard gravity beer (~1.055). If you need to go bigger, it’s typically worth buying a second dry yeast pack rather than making a starter. There’s nothing wrong with using dry yeast, and you can make a fantastic beer that way. However, there just doesn’t exist the same variety in dry yeast that there does in liquid form.

Making a yeast starter was a daunting task to me as a new brewer, and it took me over a year to really start tackling that aspect of brewing. Our local homebrewers are fortunate enough to have access to homebrew-sized Escarpment Labs pitches. These vials of yeast contain approximately 200 billion packaged cells, and have not been subject to the stresses incurred during international shipping. This is enough yeast for standard-strength 5 gallon sized batches (< 1.065). They are available fresh where quality brewing ingredients are sold. However, for bigger batches, older yeast, or yeast vials that contain much fewer yeast cells than required, a starter is a great way to ensure a healthy, vigorous fermentation. Hopefully this post helps anyone starting to get into liquid yeast, or hasn’t made the leap yet because they think propagating yeast is an advanced skill. If you can make a beer, you can make a yeast starter. Trust me, it’s super easy!

While writing this post, I was fortunate enough to get to ask Richard Preiss from Escarpment Labs a few questions about yeast starters. I have posted snippets of that conversation throughout the post.

What is a yeast starter?

A yeast starter is basically a miniature beer that has the optimal conditions for yeast growth. They are typically unhopped and between 1.030-1.040 in gravity. The goal here is to make yeast, not tasty beer! Depending on the amount of yeast you are planning on growing, a typical starter can range in volume from anywhere between 500 mL to 5 L for a 5 gallon batch. I’ll get into starter sizes a little later.

Why a yeast starter?

  • You don’t want your yeast to be stressed out when fermenting your beer. Pitching enough yeast will ensure a quick and complete fermentation, prevent off-flavors, and lead to a better tasting beer.
  • You can help prepare the yeast for fermentation. Yeast sitting in the fridge for 6 months may have lost some vitality and gotten lazy. Get them ready to do the job.
  • A test to see if your yeast are still viable. With older yeast, it’s much better to find out from your starter that your yeast are dead than it is from your 5-10 gallon batch of beer!
How important is pitch rate in a yeast starter? Are concerns with underpitching in starters more of a “contamination window” issue or yeast health issue?
Richard: It all depends on the yeast strain! Some are much more flexible about underpitching than others. For example, Weizen, Belgian and Saison strains often don’t have much trouble with underpitching, and might actually be more expressive. But some yeasts like lager yeasts really do benefit from higher pitch rates. That being said, yeast pitch rate doesn’t tell the whole story. Yeast cells should also be relatively fresh, and high vitality, meaning they get to work on fermentation quickly. If the yeast is relatively fresh and already a good cell count (like our homebrew pitches), you can always use a “vitality starter” (small starter early on brewday) to kick the yeast back into action after some fridge-inflected dormancy. I wouldn’t worry too much about underpitching starters – most commercial liquid yeasts have more than enough cells, even at 3-4 months old to ensure fairly reliable growth.
How much of the benefits of a yeast starter can be attributed to an increase in vitality vs. an increase in viability?
Richard: It definitely helps with both! However, in our experience (and in empirical data collection), vitality and viability are fairly strongly correlated, in that yeasts tend to lose vitality as they die and lose viability. So a starter helps solve both problems if the yeast is a bit old.

What size should your starter be?

The size of the starter you make depends on a few factors. In general, a larger starter means more yeast growth. It is helpful to find a starter calculator you like and use it to determine the size of starter to create. A list of some common calculators are:

What you need

Once you determine the volume of starter that you need, you can start to make the starter! Some of the above calculators will tell you the amount of DME and water to use, but a good general rule of thumb for starters is 100 g of DME per 1 L of starter wort (or 1 g/10 mL).

  • A pot with a lid to boil the wort in
  • Yeast that you want to grow
  • DME
  • water
  • A sanitized vessel for the prepared wort, clear is best. A 2 L vessel will work well for most ales, while a larger 4-5 L vessel may be required for high-gravity lagers. I prefer a borosilicate erlenmeyer flask as I can easily boil the wort inside of it to sanitize, but any sanitized vessel will do.
  • Aluminium foil or a foam stopper.
  • Optional: stir-bar and stir-plate.
  • Optional: funnel.
  • Optional: Yeast nutrient (~ 1/8 tsp).
Is yeast nutrient important in yeast starters?

Richard: If you’re making a yeast starter from LME or DME, I would recommend adding a yeast nutrient as we’ve found that malt extracts tend to have a lower micronutrient concentration than all-grain wort. We’ll be rolling out our own yeast nutrient, tailored to optimize popular strains like Vermont Ale shortly!

Preparing the starter

Preparing the starter is as simple as making a tiny beer. I’ve also included a link to a video of the process in the “Additional Information” section at the bottom of the post.

To make a starter:

  1. Measure out your water
  2. Weigh your DME and combine with the water in the pot until all chunks are dissolved (this would also be the time to add your nutrient).
    Getting DME and yeast nutrient ready for a starter since White Labs only supplies you with half of the yeast cells that Escarpment Labs does.
  3. Boil the wort for at least 5 minutes (I boil the wort in an erlenmeyer flask).
    Boiling wort in an erlenmeyer flask to sanitize the wort and flask.
  4. Cover the pot with a lid that has been sanitized.
  5. Place the pot in a water bath and allow to cool to below 30 C. You can use a sanitized thermometer if you want, but a perfect temperature isn’t necessary.
    Chilling the yeast starter in a water bath in my kitchen sink. This takes about 20-30 minutes unattended.
  6. Pour the wort from the pot to the sanitized starter vessel.
  7. Pitch your yeast!
  8. Cover with sanitized aluminium foil or a foam stopper. This is important. The stopper and the foil will keep the bugs out (they don’t have legs to crawl up and under the foil). However, an airlock does not allow oxygen to get into the fermentor during fermentation. Yeast grow better when they are exposed to oxygen during growth!
  9. Shake the starter frequently (the more the better) to introduce more oxygen, remove CO2 and keep the yeast roused (I use a stirplate so that I can set it and forget it).

Around 24 hours later, your starter is ready! You can usually tell visually that the yeast has grown. Some high-flocculating yeasts will produce large yeast chunks while others will just create a lighter-coloured, cloudy starter due to all of the new yeast cells in suspension. This is a good sign that your yeast were viable and they are ready for action. If you won’t be using your starter right away, you can put it in the fridge for later.

The yeast starter at various stages of growth: (Left) Right after the yeast has been pitched, (Centre) 8 hours following the yeast pitch, (Right) 24 hours following the yeast pitch.

Be mindful of sanitation! Remember, this is just like making a tiny beer.

Not necessary, but my personal take:

I use a borosilicate flask so that I can boil my wort inside of it, put it directly into the water bath, and then eventually pitch the yeast into it without transferring. It’s easier and has less risk of contamination. A stir bar and magnetic stirrer takes over the job of shaking for you. I also usually put my starter in the fridge for 24 hours before brewing and decant most of the wort off of the yeast cake right before pitching the yeast slurry. Don’t try to boil in a flask with an electric stove element!

What is the optimal temperature for yeast starters? Can more time counter the effects of lower temperature and vice versa or are there other things at play?
Richard: Yeast are also very amenable to a range of temperatures during propagation. We’ve found that most yeasts will handle anywhere from 20-30 ºC. However we don’t like to let lager yeasts propagate over 25 C as this helps maximize their cell health. But warmer propagations will help maximize the rate of yeast growth – which peaks around 30 ºC. More time certainly can counter the effect of lower temperature, but most yeasts do have a “temp minimum” below which they will be extremely sluggish – below 18 C for most Belgians and Weizens, below 20 C for most Saisons, below 15 C for most clean ale strains, and below 8 C for lager yeasts.


What are the best homebrewer-accessible “yeast count” measurement methods?
Richard: In general, most yeast slurries (such as those that settle in finished beer, or in a cold-crashed and decanted starter) end up in the 1-3 billion cell / mL range. 

Our general rule of thumb is: 

For flocculant yeasts
–  an unpourable, sludgy slurry is ~3 billion cells / mL. 
– a chunky, tricky to pour slurry (think pancake batter) is ~2 billion cells / mL. 
– a fairly free flowing but turbid slurry is ~1 billion cells / mL 

For non flocculant yeasts 
– a pancake batter-like slurry is ~3 billion cells / mL 
– a fairly free flowing but turbid slurry is ~1-2 billion cells / mL 

You can then look at how much yeast you have, and estimate how many billions of cells you have and compare that to a pitch rate calculator to determine how much to add to the next brew.


And that’s it! Yeast starters are an easy way to improve your beer and ensure you get the best fermentation possible. I’d like to give special thanks to Richard Preiss for taking the time to answer some of our yeast starter questions.


Additional Information