Splitting A Wyeast 1272

[jakester]

Planning on brewing on the weekend, first one in months, cracked our grain last night in preperation and checked what we have. For the yeast we have just one pack of Wyeast 1272 American II in the fridge. As i brew with the neighour, we do @40L batches and split the wort, then do our own things with our own yeast. Now with just one pack, what is the correct method for making a starter to make enough cells for each of our 20L brews. I have made starters before from smack packs for single batches but want to get it right and not just wing it and get inferior results for a larger brew. Do we just halve whats in the pack, then make our own starters or make a large starter and halve at the end before pitching? Or will one pack have enough to ferment 2 x 20L batches?
Any help is greatly appreciated!

 

[mika]

Depends on the gravity, but think you'd be better building it up and splitting at the end. For a regular brew, probably ~2L worth of starter per batch.

 

[warra48]

Pitch the pak into say 4 to 5 litres of wort, and encourage it as much as possible to grow.
You'll have enough yeast to do both batches.
I don't think a 2 litre starter from a new pak of yeast will give you much in the way of growth.

 

[mika]

Just to clarify, I meant 2L per batch after building, so yes, 4-5L initial starter.

 

[mintsauce]

If you've not seen this before: http://www.mrmalty.com/calc/calc.html a Yeast Picing calculator.

 

[jakester]

thanks for the replies!
I was thinking about the pitching calcs but need the time to run through them so i thought i would post here first. Just had a quick look and they have an iphone app, might do that and check it out. A bit off topic but got iBrew on the iphone last night, just to keep all my recipes in order. It looks good so far, even has a mash and hop timer/alarm!

 

[Pennywise]

Brew Pal is good also

 

[Wolfy]

I have made starters before from smack packs for single batches but want to get it right and not just wing it and get inferior results for a larger brew. Do we just halve whats in the pack, then make our own starters or make a large starter and halve at the end before pitching? Or will one pack have enough to ferment 2 x 20L batches?

One newly manufactured pack of Wyeast yeast is designed to be pitched directly into 5US gallons of average gravity wort.
Outside of that the best information as to what size starter you need is the MrMalty calculator linked above, or the similar tool on Wyeasts website (which is nice in that it allows for 1/2 packs, but does not include date of manufacture and only works on US measures which is limiting).