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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.

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Aren't books pre-internet too? –  brewchez May 6 at 12:02

2 Answers 2

up vote 2 down vote accepted

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.

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What a handy tool! I don't even know what a stir plate is, but I will soon. Much obliged. –  Glasseyed May 5 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 May 5 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 May 5 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.

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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 May 6 at 13:10

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