Making a Yeast Starter

You may ask: “Why do I need a yeast starter? I have a vial of yeast that says it’s good for a 5 gallon batch”. The answer is this site is about turning good beer into great beer. The standard slap pack or vial does not contain enough yeast for a quick and clean fermentation. See the yeast section for more information.Optional Equipment for a Yeast Starter

Here is a list of standard items used in a yeast starter setup:

  • 2 liter Erlenmeyer flask or 2 quart pot
  • tap or brewers water (chlorine free and not all distilled)
  • Extra Pale DME (dry malt extract)
  • brewer’s yeast (ale or lager)
  • Optional items:
    • 1) Yeast nutrient (from Wyeast or White Labs) will provide optimal nutrition for the yeast to duplicate.
    • 2) Anti-foam [Dow Corning FG-10 a food grade silicon based foam reducer or FermCap®] will help keep the DME from boiling over.
    • 3) Phosphoric acid lowers the pH to the preferred range for yeast (range: 4-6, preferred pH: 5.0).
    • 4) A pH meter will measure the acidity of the water.
    • 5) A stir plate may be optional, but you can double the amount of yeast over the same size starter when using one and it helps reduce CO2 which is toxic to yeast; the alternative is to swirl it often over 2 days.


The yeast should be stored in the refrigerator, wrapped in a small towel to regulate temperature, and then removed from fridge before starting this process. I find that the yeast comes up to the correct temperature range by the time it is ready to pitch.


Please note that this is a yeast starter, and although it is essentially beer, it is a bad recipe. A yeast starter is designed to duplicate the yeast and make sure it is lively and viable. These processes should not be duplicated when fermenting beer which is designed for taste.




Step 1) Calculate how many yeast cells are needed for your brew. Use software or check out the yeast section. Add (quantity of water from software) amount of brewing water. The minimum is 1 liter. Any less and the yeast do not have enough resources to effectively duplicate.


Step 2) In the flask or 2 quart pot, add the brewing water first, then the DME to a ratio of 100 grams DME to 1 liter water for a gravity of about 1.035. It will be clumpy and messy, but when it warms it will go into solution. Add the optional items: anti-foam (1/8 tsp FG-10 or 1 drop FermCap®), 1/8 to ¼ tsp yeast nutrient, and phosphoric acid to a pH of 5.0.


Step 3) Place the flask or pot on the stove and boil for 15 minutes.15 minute boil If using a stir plate, you can boil the Teflon® stir bar. Do not drop it in the flask, but slide it down the side to minimize the risk of breakage. [Note: an Erlenmeyer flask is designed to take direct heat from a gas flame but not from an electric stove where the metal elements are exposed. Glass top should be fine. When in doubt, use a square wire pad with ceramic fiber between the flask and heat source.] Be careful of boil over. The anti-foam helps, but it can still overflow. Adjust or remove from heat to help control it. I use a flask. In order to adjust for the reduction in liquid, I add the water to the full quantity then add the DME. This usually compensates for the reduction. If using a pot, then add a little more water. The boil reduces faster in the pot.

At 2 minutes, cover with sanitized foil

Step 4) Cover the flask or pot with sanitized foil (I spray the foil with Star San® and loosely cover the flask while boiling for the last 2 minutes).


Step 5) Place covered container in a water bath – no ice, yet. Once it has cooled to 130˚ F or so, replace the water and add ice to reduce the temperature to about 70˚ F. Other wise, the ice will melt and you'll still have hot wort.

First a water bath with no ice.        Then a water bath with ice.

Temperature is close -ready to pitch yeastStep 6) Time to pitch the yeast, but first, read on… The yeast temperature should be within 10˚ F of the starter (preferably 5 F). Sanitize yeast vial or smack packSpray the yeast vial or smack pack with sanitizer – also the scissors, funnel, and even your hands. Aerate the starter for 30 minutes before pitching the yeast. The starter temperature should be between 65˚ F and 80˚ F. As the yeast work to ferment the starter, the temperature will increase. Though some yeast can survive up to 100˚ F, it is better to keep the temperature below 85˚ F.


Aerate starter for 30 minutes before pitching yeast

2 days later... ready to chill

Step 7) Leave the starter covered for two days. If you’re not using a stir plate, then make sure to swirl the starter often (30 minutes) over the 2-day ferment. Starters are usually done in 24-36 hours because there is so much yeast and so little sugar. However, when done, the yeast needs to build up their storage supplies. This can take about 12 hours (48 hours total though more time will not hurt).


Step 8) Place the starter in the refrigerator for 24-48 hours before using. This helps settle the yeast to the bottom so the liquid can be decanted off the top.


Step 9) On brew day, with the container still covered, remove the starter from the refrigerator 2-3 hours before pitching and wrap with a clean towel. This will make the temperature change less drastic for the yeast.


Step 10) Pitch the yeast. Carefully decant all but a cup of liquid from the starter leaving the yeast cake intact. Make sure the yeast and wort temperatures are within 5˚F of each other. Then swirl it around to rouse the yeast cake and pitch it into the aerated wort in the fermenter.

Boil without


Boil with







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