Within the next few days I'll be 'brewing' 100 litres of ale from slightly concentrated sterile wort. I've used these kits before with decent results, but this time I want to try a liquid yeast instead of the packaged dry (Cooper's) yeast that's included in the box. So I bought a Wyeast 'Direct Pitch' smack pack (British Ale II) that allegedly contains 100 billion cells.

Not enough for this much wort, obviously, so I propose to boil up half a pound of dry malt extract to make a 1/2 gallon starter. When that's rolling nicely I'll use it to pitch this next mega-batch. Good idea? Bad idea? Any reason that wouldn't be satisfactory?

Much of my homebrewing knowledge, if you can call it that, dates back to Neolithic (i.e. pre-Internet) times, so until I can lay my hands on some good recent books on the subject, I thought I'd ask the question here.

  • 1
    Aren't books pre-internet too?
    – brewchez
    Commented May 6, 2014 at 12:02

2 Answers 2


1/2 gallon (~1900mL) will probably net you about 350bn cells (if you have a stir plate, yeast isn't too old, &c.).

For 100L of ~1.040 wort, you want closer to 750bn cells (depending on gravity, assuming an ale).

Use a pitch rate and starter calculator to get a better sense of your requirements for yeast and the the sizes/steps of starter needed to get to those pitch rates.

  • What a handy tool! I don't even know what a stir plate is, but I will soon. Much obliged.
    – Glasseyed
    Commented May 5, 2014 at 18:41
  • Back with an instant update. Found this link, in case anyone's interested: byo.com/stories/projects-and-equipment/item/… Now that I'm getting back into home brewing, I'll probably build one myself, since it turns out I have all the necessary components. In the meantime I'll adjust my starter recipe to suit my present equipment.
    – Glasseyed
    Commented May 5, 2014 at 18:49
  • Nice. There's a significant difference in yeast starter growth between a stir plate and other methods; the brewers friend calculator has some references, especially to Kai's measurements. Yeast health and fermentation temp control are probably the two biggest improvements most homebrewers can make. Cheers!
    – jsled
    Commented May 5, 2014 at 19:38

Obviously you know now that you are under-pitching with the 1/2 gallon starter idea.

For 100L you'd need several stir plates going really. IMO, the best bet would be to brew a standard 20L batch, then use that entire cake as the pitch for the 100L batch.

  • 1
    I'd be seriously underpitching, so I'll take your advice. As for books being pre-Internet--got a mild chuckle out of that--my modest home brewing collection dates back to the 70s and early 80s, when the general level of (accessible) knowledge was pretty abysmal compared to now.
    – Glasseyed
    Commented May 6, 2014 at 13:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.