How To – Make a Yeast Starter

Ahhh. The big question. Should I make a yeast starter? Yes! Of course you should! In order to understand why, we first need to go back to the basics. Grab a beer, sit down, and relax. You’re about to learn how to take your beer to the next level by using a yeast starter.

What is a yeast starter? It’s basically a mini, unhopped beer that is fermented with oxygen exposure for the purpose of making healthy, happy yeast, and more of it.

Have you ever tasted hopped wort at the end of the boil? It generally tastes pretty awful – both sweet and bitter at the same time. Have you ever tasted beer? Of course you have! What does this have to do with why you should make a yeast starter? Yeast is the single ingredient responsible for the remarkable flavor change from nasty hopped wort to delicious beer. Don’t get me wrong, some hopped wort does taste pretty good, and unhopped wort is generally awesome, but this means three very important things for beer brewing:

  • Yeast is the single most important ingredient in beer
  • Taking care of your yeast should be at the top of your priority list (yes, above switching to kegging your beer)
  • Using a yeast starter = great beer. Great beer = happy you. By the transitive property of equality, using a yeast starter = happy you!

What does yeast do during fermentation? Yeast eats sugars in your wort and gives off:

  • Flavor (known as esters)
  • Alcohol
  • CO2

Note that I put flavor at the top of the list. Most home brewers will say that yeast eats sugar and gives off alcohol and CO2. Hearing someone say this excluding flavor makes me sad. There is a reason that White Labs and Wyeast have close to 100 different yeast strains to choose from. Flavor! Given that the people at yeast companies work extremely hard on maintaining their own vast libraries of strains, the fact that they mostly sell one strain of yeast when there are so many others to choose from probably also makes them sad.

That being said, it is very important to not get caught in what I like to call, the California Ale (WLP001) / American Ale (Wyeast 1056) / Safale US-05 trap [arguably 3 offerings of the same strain of yeast]. Just because a recipe calls for one of these three strains does not mean that you can’t use a different yeast. Many times, I’ve heard people say “I’m just going to use California Ale, it works great for me every time.” A much better train of thought when selecting yeast is to choose the yeast whose description sounds the best for what you’re trying to go for flavor-wise with your recipe. All yeast strains will work well every time if you take proper care in handling and fermenting with them. Don’t get me wrong, these three yeasts will make great beer, but they are massively overused. Try White Labs’, Wyeast’s, and Safale’s other strains too! You don’t know what you’re missing out on unless you brew with it! If you’re a White Labs fan like me, be sure to check out their Platinum strains too. Belgian Saison III (WLP585), a Platinum strain, is by far my favorite yeast strain above all others. I’m glad I tried it, and I wish it were available year-round! C’mon White Labs! Help a brewer out!

Be adventurous! Have you ever wondered what gives a hefeweizen banana or clove character? It’s the yeast. There aren’t any bananas or cloves in the beer. What about the pear-like character in Duvel? That’s also the yeast! As you can tell, beer yeast gets me excited, and I hope I’m able to get you more excited about yeast!

Different Types of Yeast Starters

I first want to clear the air on the different types of starters. There is only one proper way to do a yeast starter at home, and that is with a stir plate. I’m sure you have heard of people making starters with growlers and an airlock, swirling around the yeast every time they walk by the growler. While a growler starter will help reduce lag time (simply put, the time it takes before the airlock or blow-off tube starts bubbling), it neglects one of yeast’s favorite things: oxygen. This is where the stir plate comes in.

A stir plate yeast starter is meant to be done in a semi-open vessel, allowing oxygen to flow into the yeast starter and make the yeast cells happy and able to reproduce. Stir plates also help degas CO2 released by the yeast from the starter by continuously stirring the starter. Think about it like you’re continuously stirring a soda – it would quickly become flat. This is good for the yeast because it keeps the starter aerobic (oxygen-rich), and this is the phase of fermentation where yeast reproduces most easily. Anaerobic (the growler with the airlock example) means you’re not creating an environment that is friendly for the yeast to reproduce, which is the whole point of a yeast starter.

It’s like Building a House… Sort Of

Now why would you want more yeast cells to ferment with? The real question is why wouldn’t you want more yeast cells to ferment with? Think about it like this: you need to build a house from scratch in 3 weeks. If you had a team of 4 people working non-stop, they may be able to get it done in time, but they’re going to be massively over-worked and as a result, the sweatiest, stinkiest group of people you’ve ever been around, and the build quality of the house would suffer. What if instead you had a team of 50 people doing the same task in the same timeframe? They might not even break a sweat. Better yet, what if you were able to throw a big air conditioned dome over the build site and control the temperature to keep the workers from breaking a sweat? Yup! Fermentation temperature is just as important as yeast health (but we’ll save that for another post). Although we generally don’t measure the build quality of a house by how clean the workers smell after building it, this is how you should look at yeast and fermentation. Fermentation is teamwork – the more players involved, the better the end product.

Now that you have a solid way to look at yeast, let’s get started with starters!

Making Your First Yeast Starter

Equipment you’ll need:

  • 2 L Erlenmeyer flask
  • Stir bar
  • Aluminum foil
  • Stir plate
  • Freezer space
  • Oven space

Ingredients you’ll need:

  • Extra light / pilsner dry malt extract
  • Yeast nutrient
  • Reverse osmosis or distilled water (the chlorine found in most tap water inhibits yeast growth)
  • Your favorite yeast strain!

Picture of a vial of WLP585 sitting on the counter, warming up to room temperature.

Now, on to the process! The first thing you’ll want to do is consider the yeast you’re using. Get your yeast ready by following the directions on the yeast’s packaging. In this case, I’m using my all-time favorite yeast, WLP585. Some yeast strains like those from White Labs require you to let them warm up to room temperature prior to pitching. Others, like Wyeast, require you to activate their “smack pack.” Whatever the case, consider the time delay it takes to prepare the yeast for pitching before you get your starter ready for inoculation.

When it comes to dry yeast, even if the packaging tells you to activate the yeast in warm (~95-100ºF water), skip that. Simply add the dry yeast directly to your starter. I can’t even begin to tell you how many times I’ve had people call in to the home brew store telling me that they tried to activate their dry yeast, according to the packaging (calling for rehydration in 100ºF water), and after 48 hours, they have zero fermentation activity. This is likely because of inaccurate thermometer measurements when adding yeast to the hot water. The problem with the method called for on the back of some dry yeasts, is that the re-activation temperature is so dangerously close to the temperature at which you will kill most saccharomyces yeast strains. If your thermometer is off by even 5 degrees, you could end up killing your yeast. Right now, as I write this post, I know that Lallemand still calls for a similar rehydration method, whereas Safale now says to “sprinkle yeast into wort” for pitching directions. My guess is that eventually Lallemand will follow suit. Long story short, when working with dry yeast, don’t try to rehydrate it unless you really really trust your thermometer’s calibration.

Picture of the digital control panel of an oven pre-heating to 170ºF.

Next, pre-heat your oven to 170ºF. I look at an oven as an opportunity to “autoclave” brewing equipment. Why make a big mess with sanitizer when you can use an oven? In fact, my method for preparing a starter does not require the use of sanitizer. This is awesome for those of us who are trying to brew more professional quality beer while keeping the process very clean and simple. I usually let the oven come to temperature and hold for 20 minutes.

Picture of a 2 liter Erlenmeyer flask sitting on an electric stovetop.

Now for a bit of multitasking. While we wait for the oven to come to temperature, let’s get the starter’s wort prepared. First, grab your 2 L flask. For me, a standard starter is a 1.5 L starter. Since I make my starter’s wort in saucepan, I usually prepare 2 L of wort to account for any wort that is spilled while pouring into the flask (my saucepan is not ideal for pouring – one of these days, I’ll be buying a new one).

Picture of a 2 liter Erlenmeyer flask sitting on an electric stove being filled by a water jug.

Since our 2 L flask is graduated, we may as well use it to measure out our water.

Picture of a 2 liter Erlenmeyer flask filled to the 2 liter mark with water.

Measure out 2 L of water.

Picture of a stainless steel saucepan sitting on an electric stovetop.

Get your saucepan ready. Mine has about a 3.5 L capacity.

Picture of water being poured into a stainless steel saucepan sitting on an electric stovetop.

Pour the 2 liters of water you measured in your Erlenmeyer flask into your saucepan.

Picture of a stainless steel saucepan on an electric stovetop with the burner set to hi.

Turn up the heat! We’re looking to bring this to a boil. Now for more multitasking. We’re going to measure out the dry malt extract and yeast nutrient for the boil.

Picture of dry malt extract on a food scale.

For 2 L of starter wort, we want to use 200 g of extra light / pilsen / pilsner dry malt extract (it goes by a few different names). This will get our starter’s specific gravity where we want it to be. As malt extract can vary significantly in “fluffiness,” it is important to make your measurements by weight rather than by volume. I have packaged malt extract by weight where sometimes it takes up as much as 3/4 of the bag I’m using, whereas other times it takes up only 1/3 of the same-sized bag. This is because of varying packing density. When in doubt, weigh it out!

Picture of yeast nutrient being held in front of a bowl of malt extract on a kitchen scale sitting on a counter.

Since the whole purpose of making a starter is to grow the cell count and make the yeast happy, we may as well throw in some yeast nutrient. I like to use White Labs’ WLN1000 nutrient. Most cheap yeast nutrient is only diammonium phosphate, whereas the WLN1000 is diammonium phosphate, vitamins, minerals, and more. I look at cheap yeast nutrient like a human supplementing with vitamin C. I look at the good nutrient (something like WLN1000) like a human supplementing with a multivitamin that also includes vitamin C. That’s just how I see it; feel free to use whatever nutrient you like.

Picture of 1/8 teaspoon of yeast nutrient being added to a bowl of malt extract.

I add 1/8 TSP of yeast nutrient to my starters. If you’re using the White Labs nutrient, be sure to stir it into your dry malt extract before adding to the water we are bringing to a boil – their nutrient tends to cake easily. Once your saucepan of water comes to a boil, kill the heat, add your dry malt extract / yeast nutrient mixture, stir it in, and turn the heat back on. We want to boil this gently for about 10 minutes. The length of time for the boil is not very important like it is with the wort for the beer itself – we simply want to make sure the wort is sterile, so we boil it for a bit.


While we’re waiting for the water, dry malt extract, and yeast nutrient to come to a boil, we need to bake our flask to sterilize it. Some people use a foam stopper for their flask, but I prefer to use aluminum foil to cover the flask. I like brewing with materials that I can throw in the oven to sterilize. Tear off a square sheet of aluminum foil and fold it in half twice (see picture below).

Picture of folded-up foil sitting on the counter next to an Erlenmeyer flask.

This foil will be placed on top of the flask and secured around the top.

Picture of the bottom of an Erlenmeyer flask with a stir bar in it.

Don’t forget to add your stir bar to the flask before putting the foil on top!

Picture of a 2 liter Erlenmeyer flask covered in foil sitting on the counter.

Secure the folded up foil to the top of the flask as shown above.

Picture of a 2 liter Erlenmeyer flask with foil on the top sitting in an oven.

Place the flask (containing the stir bar) covered in foil in the pre-heated oven and close the door. In my experience, baking the flask for 30-45 minutes at 170ºF does the trick, but you can always increase the oven temperature to 220ºF after about 10 minutes, if you wish.

Picture of a saucepan of malt extract with water boiling.

Eventually the dry malt extract / nutrient / water will come to a boil. Boil this mixture for about 5-10 minutes. Time it so that you take the flask out of the oven at about the same time that you kill the heat for the boil. If you’re off by 5-10 minutes and your boil is done before the flask is done baking, don’t worry about contamination, you’re not going to have a wild yeast survive in liquid that is still at 190ºF.

Picture of wort being poured from a saucepan into an Erlenmeyer flask.

Once the flask is ready, place it in your sink, remove the foil top (do not crush it – set it on the counter upside down because we will use it to reseal the top of the flask) and pour the wort from the saucepan into the flask. I usually shoot for just below the 1.5 L mark (about 1.4 – 1.45 L), as the yeast vial will add a little bit of volume to the starter.

Picture of rinsing off the outside of a 2 liter Erlenmeyer flask filled with wort and nutrient for a yeast starter.

As the previous step will make you spill wort all over the sides of the flask, carefully rinse off the sides of the flask to rinse off the malt sugars – you don’t want your flask sticking to your stir plate. I rinse off all the way up to where I’m right below the lip on the top of the flask. Be very careful to not get tap water into the starter. An alternate method would be to take a washrag soaked in sanitizer and wipe off the sides, top, and bottom of the flask.

Picture of an Erlenmeyer flask sealed up with aluminum foil, sitting in a kitchen sink.

Place the foil back on top of the cleaned off flask and cinch it down securely to the top of the flask.

Picture of an Erlenmeyer flask with wort in it, sitting in a freezer to cool down.

Place the hot flask with hot wort in it, in the freezer. I recommend setting it on a hot pad or two before placing it in the freezer. While your flask is likely borosilicate glass, the glass shelving in your freezer is most likely not. You don’t want to shatter the shelf in your freezer! Even if you have metal shelving, it’s still a good idea for both the freezer shelf and your flask to put a hot pad down first. Close up the freezer and wait for it to cool down. Depending on your freezer and whether or not the compressor / airflow is running, cool-down times may vary. For me, it’s usually about 1-2 hours. Every 15-20 minutes, open the freezer and put your hand on it below where the wort is. You want it to be cool to the touch, but not cold. If you want, you could check the temperature of it, but that would be one more thing to sanitize. For ales, you will end up doing them at room temperature (72ºF – 78ºF). If the beer you are making will be fermented at 68ºF and you do the starter in a room that is 78ºF, contrary to what some books say, in my experience, there is no notable difference in yeast propagated at a warmer temperature than the fermentation. When doing a lager however, you do want to do the starter close to the same temperature as the fermentation, which means throwing your starter and stir plate into a refrigerator with a controller on it.

Picture of pouring a vial of yeast into an Erlenmeyer flask on a stir plate.

Once the starter is cool to the touch, place it on your stir plate, get the starter stirring, and add your yeast. (You’ll have to excuse the picture above – it’s in my old apartment and I’m using a different vial (don’t worry about it). I shot pictures for this tutorial while I still lived there, but when I moved, I decided to re-shoot the pictures. The action shot of me pouring the yeast into the starter is a one-time shot, and it was blurred when I tried to shoot the same picture in my new house. Fortunately, the apartment version turned out great, so we’ll pretend like we didn’t notice anything different here.)

Picture of a stir plate yeast starter.

Back to the new bathroom now. Secure the foil back on top of the flask, but don’t cinch it down 100%. I leave a small gap on one of the sides of the top of the foil so that air can flow in and out of the flask more easily. Don’t make this gap very big – you don’t want your starter fully open to the elements to where it could capture wild (undesired) yeasts. This is what the stir plate starter will look like after pitching yeast. The bubbles around the top are not yeast activity yet.

Picture of an active stir plate yeast starter.

Between 4-24 hours, your starter will look something like above. The foam is the result of the yeast releasing CO2 as it ferments the starter. My rule is to leave the starter on the stir plate for 48 hours, then place it in the refrigerator for 48 hours. Two days on the sir plate gives the yeast plenty of time to propagate. Two days in the refrigerator allows the yeast cells plenty of time to floculate (group together and drop out of suspension, to the bottom of the flask).

Picture of a 2 liter Erlenmeyer flask in the refrigerator.

After 48 hours on the stir plate, fully secure the foil down and place the flask in your refrigerator for 48 more hours.

Picture of a 2 L Erlenmeyer flask after cold crashing - yeast is at the bottom.

After 48 hours in the refrigerator, you will notice the yeast has dropped to the bottom of the flask. 3-6 hours before you’re ready to pitch your yeast on brew day, remove the yeast from the refrigerator. Remove the foil and place it upside down on the counter. Decant most of the liquid from the starter, being careful to not pour any yeast from the bottom out, also leaving enough starter behind to be able to swirl around to break up the yeast at the bottom. Cover the decanted starter back up with the foil and leave it on your counter at room temperature, allowing it to warm up to room temperature prior to pitching the yeast into your beer. Once it has warmed up, when you are ready for pitching yeast, remove the foil once more, place your keeper magnet (a magnet to hold the stir bar from falling into your fermentor) on the flask, and pour the yeast into the wort for your batch of beer. If you forget to use the keeper magnet and you pour your stir bar into the fermentor, do not panic. You can simply leave the stir bar in the fermentor until your beer is done fermenting (2-4 weeks) with no harm to your batch. If you make this mistake, don’t forget to retrieve your stir bar when you transfer out of your fermentor!

There are many different methods to go about doing a yeast starter. This method is one that I came up with that works very well for me. I have brewed 30 or 40 batches of beer using this method for my starter, and I have yet to have a contaminated batch of beer, so I must be doing something right!

To recap the quantities and times: 2 L water to 200 g DME. 2 days on the stir plate. 2 days in the refrigerator.

Have fun and remember to try different yeasts!



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