Making a yeast starter

Basic instructions for how to make a starter, and guidelines for sizing the starter to the batch.

Follow these simple instructions to kick-start your fermentation by maximising yeast health and vitality.

Note: The whole process, from boil to pitch, can be done in a heat resistant glass chemistry flask if you have one (the bigger the better).

Create your wort

  1. Bring your water to the boil
  2. Add DME (100g per litre for 1.040 SG)
  3. Add yeast nutrients (check instructions to work out how much to add)
  4. Boil for 15 minutes
  5. Cover with aluminium foil
  6. Cool to fermenting temperature (18-24C)
  7. Shake to aerate
  8. Pitch yeast (see below)
  9. Periodically swirl/gently shake to re-aerate
  10. After 12-24 hours the yeast will reach peak density and high krausen. You can place the starter in a refrigerator for 24 hours to drop the yeast out of the beer now if the OG of your brew wort is the same as the starter, or wait until the starter fermentation has completed and the yeast are floculating and storing energy for their next fermentation if not.
  11. Once the yeast have dropped out of the starter beer, decant as much of the liquid from the starter as you can before pitching to your brew wort.

How big a starter?

How much yeast to add to how much wort will depend on the specific brew you're creating a starter for. As a rule of thumb, a 23-litre batch of lager with an OG 0f 1.050 will need approximately 425 billion cells (2). Ales require approximately half this amount(3).

Each 0.05 variation to OG requires an adjustment 0f ~40 billion cells (up or down, as required). So, for a 1.055 OG lager brew you'll need 465 billion cells and for a 1.045 OG brew, you'll need 385 billion cells.

Typically, a liquid yeast pack will include 100 billion cells, but some have more (e.g. Bluestone, who claim "over 200 billion live cells").

So, for a 1.055 OG lager you'll need approx. 4.5 standard packs of liquid yeast. If you have 4.5 packs, you probably don't need to bother with a starter.

If you want to save some money, using 2 standard packs of yeast (200 billion cells) in a 3 litre starter will give you a growth ration of approximately 2.3x (3), resulting in 460 billion cells.

(1) Jamil Zainasheff, Brewing Classic Styles p. 286
(2) John Palmer, How To Brew, p. 116
(3) Randy Mosher, Mastering Homebrew, p. 214
(4) John Palmer, How To Brew, Table 7.4, p. 119