Yeast Harvesting From A Starter The Overbuild Method

Yeast harvesting from a starter the Brulosophy overbuild method. Harvest and reuse your yeast from a starter and don’t waste your time with washing your yeast from your frementer. Save money making a yeast starter for your homebrew. 

I overbuild my yeast starter and harvest enough to ferment 6 gallons / 23 liters of wort and save enough for a starter so that I can propagate and overbuild this yeast strain again, generation after generation. You can keep this process going and you can easily get over 8 generations.



Yeast Starter Recipe: 

1 gram DME for every 10ml of water will give you an original gravity of 1.040

• 100g DME + 1000ml water = 1.040 OG

• 200g DME + 2000ml water = 1.040 OG

If the OG (original gravity) is too far above 1.040 it creates too much of a good thing for the yeast. When the sugar and nutrient content is too concentrated it stresses the yeast out. You don’t get their full potential and there is a chance for off flavors. 

If the OG is too low there is not enough sugar and nutrients for the yeast to eat. They won’t grow to their full potential. Keep it right around 1.040 OG. In this case, bigger is not better. 


Yeast Starter Calculator:



Use the same water you use for your brewing water. Use something without chlorine or chloramine. 



• Erlenmeyer Flask – Flask-Amazon (2000ml is the smallest size my overbuild method works with) Bigger is better. 

• Stir Bar: Stir Bar-Amazon

• Stir Plate:

• Scale: Scale-Amazon

• Yeast: Brewers Choice

• Aluminum foil: Foil-Amazon

• DME (dried malt extract): DME-Pilsen-Amazon – Pilsen Malt or the lightest you can find.

• Large Pot: I use a 6 quart stainless steel pot: 6qt-Pot-Amazon

• Mason Jars: I use the 1 quart size: Mason Jars-Amazon

• Hot pad or “ove” glove: Hot-Gloves-Amazon

• Digital infrared thermometer: Infrared-Thermometer-Amazon

• Silicone Spoon: Cool Spoon-Amazon



• 2100ml of water without chlorine or chloramine. 

• Leave around 800ml of water in flask, pour the rest into a large pot.

• Add stir bar to Erlenmeyer flask before you start heating it up. This will prevent superheating.

• Add your foil lid before things get hot. 

• Add DME (dried malt extract) to pot before the boil starts. 

• Once boil starts turn down heat and simmer flask and DME for 10 minutes.

• Cool to room temperature before pitching your yeast. 

• Your yeast and wort should both be at room temperature within 2°f of each other. 

• Let it spin for 24-48 hours. 

Sanitize your jar that will hold your starter that you are saving.  

Swirl it around, and with everything mixed up and in solution pour off 700-800ml to save as your future starter.

Here is where the different methods come into play.

For either method you choose, save 700-800ml of the starter mixture you just made in a sanitized jar for your future starter. The remaining starter will be pitched into your wort. 

Method A: Save 700-800ml of the starter mixture into a sanitized jar for your future starter. Pour the remainder of your starter mixture into clean sanitized jars with lids, or you can keep the remainder in the flask. Put them in the fridge to chill for 24-36 hours until all the yeast has settled into cakes on the bottom of the jars. Decant (pour off) the supernatant (liquid on top of the yeast cakes). Be careful not to disturb the yeast as you pour off the liquid. Keep enough liquid so that you can swirl the yeast into a pourable slurry, around 200ml. 

Method B: Save 700-800ml of the starter mixture into a sanitized jar for your future starter. Keep the yeast for your wort in the flask. You can pitch all of it into your fermenter: the starter beer and yeast together, the whole thing. No need to decant.


Stir Plate:

You can make your own DIY stir plate can quickly get expensive. It depends on how much stuff you have laying around or what you can find for free. I made my stir plate, but it took time and money.  If I had to do it again I would probably just buy one from Stir Starters.

I’m not too sure about the quality and longevity of some of the stir plates on Amazon. 

If you don’t want to make your own stir plate, check out the ones from Stir Starters. He is a home brewer, they have a lifetime warranty, and they are under $50.




How long will it keep viable in the fridge? Up to 6 months, no problem 

Viability should be similar to commercial yeast. If the starter has been in the fridge sitting under the starter beer for more than 6+ months I do a two step starter. The overbuild calculator will help you with this. 



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