compound / Stepped starters - please check my figures

[Thirsty Boy]

Hey BN ers,

I'm doing a 50L (13.2G) batch of Russian Imperial Stout on the weekend, I've been growing me the monster starter that I think I'll need. Mr malty says that I need to start with 872billion cells - Or about 9packs of yeast. But I really want to avoid hot alcohols, so its my plan to ferment this puppy as cold as I think the Wyeast 1056 can take it - around 15-16°C (59-61°F) - so I am planning on pitching half again the Mr malty rate just to make sure I get proper attenuation. So the equivalent of about 13.5packs.

I have a 5L growler for growing starters on my stirplate, and here's what my process has been - I just want to make sure my calculations are round about correct. I fiddled with growth rates etc on the Mr malty calculator to get these figures

Nice fresh pack into 2L - onto S/plate for 48hrs = 3packs

Add DME and water to make the starter up to 4L @ 1.035

So now its 3 packs into 4L - onto S/plate for 48hrs = 8packs

Off plate and into fridge for 24-36hrs to settle. Decant beer. Allow to come back to room temperature and add 4L more of 1.035 wort

Now its 8 packs into 4L - onto S/plate for 24ish hours = circa 14packs

probably a bit less, what with losing a bit during the decanting process etc. so say 12-13packs, which is just about what I'm shooting for.

Sound right??

Please adjust my foolishness where required. Thanks

Thirsty

[chrishw]

This sounds about right, but one suggestion- why not just make a starter beer?

2L starter into a 1.048 beer= yeast cake big enough for the RIS!

As much money as you would spend in DME you might as well drink it!

[DannyW]

I'm pretty sure JZ said somewhere along the line that 12-18 hours on a stir plate will give you all the growth you are going to get, so you might be able to speed up your process without losing any growth.

Does pitching 2L of additional wort into a 2L starter really give much growth anyway? I thought 10:1 was the optimal ratio for growing these things. Something like 1 pack into 2L for 18 hours, then split that into 4x5L, then chill, decant, and pitch.

Consider if you *really* want to overpitch by that much too. You might go all the way past clean and end up with bland or one dimensional beer. You could pitch according to the calculator at 59F, then let it gently rise to the mid 60s after most of fermentation is done. That should give you the attenuation you want while keeping the fusels down early on.

FWIW I found the slurry from 20L of normal beer fermented 40L of 1.100 RIS just fine. The jug on the right is the washed cake that was swirled up and split between 2 fermenters.

[Thirsty Boy]

Hey guys,

thanks for the replys. Looks like all my reasoning went out the window anyway - that last step where I repitched the "8 packs" equivalent into 4L ... well, it went frigging berserk and volcanoed out of the 5L jug ... so now I have about 14 packs of yeast alright, its just that 3/4 of it is caked down the side of my workbench rather than in the growler.

My stirplate threw the bar overnight and while there was a pretty good chancew of the starter staying contained while the yeast was in "grow" mode - when it switched to "ferment NOW" mode the game was up.

So, I guess I will be pitching much closer to the reccomended rate, perhaps a little on teh low side now.... sigh.

Danny - I was a bit sus about the amount of growth from the extra yeast in a smaller volume of wort - but using figures off JZ's calcuator you get X cells from a Y litre starter with 1 pack of yeast - and you can also get the sme number of cells by pitching 2, 3 etc etc packs into a smaller starter. I just frigged around with the sliders till I got a sequence that made sense.

Chrishw - your most likely right, but I was using wort I pinched from work (megabrewery) and its low hopped high adjunct stuff that makes a nasty beer when you ferment it at home. A bit better planning on my part next time will see a nice scottish 60 preceed a beer like the RIP.

RIP is in no-chill cubes as I type and will be down to pitching temps by tomorrow morning, which is about when the yeast will be done.

Perfect.


Cheers

Thirsty