Yeast only fermenting only half the batch

[kev]

Hi all,
I am looking for some advice. I recently brewed an Amber ale using WLP007. I wanted to use that same yeast to ferment a Russian Imperial Stout. I usually collect about six oz of the yeast cake when I save yeast, but this time I collected a full qt. ( the imperial stout is 11 gallons). After about a week in dormancy I made a starter to revive the yeast. That went so well it clogged the airlock and I had a big mess. So I made a second starter to add to the first just to help make up what I lost.
My friend and I brewed the imperial stout (11gallons) we split the batch between 2 fermenters (5.5 gallons each). Aerated both halves for the same amount of time. I pitched the yeast into both fermenters as evenly as I could. Within 18 hours my half has blown the air lock and I had to attach a blow off tube into an empty growler( thought it was a good way of getting more free yeast). My friend's half however hasn't even begun yet. I gave him the growler that I had collected the krausing in to pitch into his half. After 24 hours he tells me that fermentation has yet to start.
When I make my starters I use 4 oz of dme with 1 qt of water which I boil for an hour with a couple hop pellets for s**** and giggles. After I cool it down I add some generic yeast nutrient I buy at my LHBS and some zinc (for good measure). I aerate the wort before I add the yeast cake that I previously collected. I have never had this problem before even when I have brewed with my friend in the past. The only difference is the amount of my starter and the OG of this current beer (1.082).
Any advice is greatly appreciated. Thank you
Cheers
Kev

 

[kev]

Hi all,
I am looking for some advice. I recently brewed an Amber ale using WLP007. I wanted to use that same yeast to ferment a Russian Imperial Stout. I usually collect about six oz of the yeast cake when I save yeast, but this time I collected a full qt. ( the imperial stout is 11 gallons). After about a week in dormancy I made a starter to revive the yeast. That went so well it clogged the airlock and I had a big mess. So I made a second starter to add to the first just to help make up what I lost.
My friend and I brewed the imperial stout (11gallons) we split the batch between 2 fermenters (5.5 gallons each). Aerated both halves for the same amount of time. I pitched the yeast into both fermenters as evenly as I could. Within 18 hours my half has blown the air lock and I had to attach a blow off tube into an empty growler( thought it was a good way of getting more free yeast). My friend's half however hasn't even begun yet. I gave him the growler that I had collected the krausing in to pitch into his half. After 24 hours he tells me that fermentation has yet to start.
When I make my starters I use 4 oz of dme with 1 qt of water which I boil for an hour with a couple hop pellets for s**** and giggles. After I cool it down I add some generic yeast nutrient I buy at my LHBS and some zinc (for good measure). I aerate the wort before I add the yeast cake that I previously collected. I have never had this problem before even when I have brewed with my friend in the past. The only difference is the amount of my starter and the OG of this current beer (1.082).
Any advice is greatly appreciated. Thank you
Cheers
Kev

Forgot to add that the temp of my half is 74* while my friend's half was 68*. He moved it from his basement into his apt to warm it up some in hopes that would help out. I also added some generic nutrient to the yeast I gave him last night. I forgot to ask him what his temp reading is. I will repost when I find out.

 

[kev]

Any ideas?

 

[ColoHox]

A temperature differential could explain the difference.

 

[Reckoning]

In addition to temperature differences, is there a chance he could have a leak in his airlock? Maybe he is fermenting and just not seeing it due to an air leak.

 

[Cyclman]

That's enough of a temp difference (almost 10%) to make a big difference with a big beer. 74 is high IMO, I'd try to cool it down.

 

[kev]

In addition to temperature differences, is there a chance he could have a leak in his airlock? Maybe he is fermenting and just not seeing it due to an air leak.

I think you might be right. My friend took a hydrometer reading tonight and it was down to 1.043. He swears that the airlock never moved. I am happy for him that all seems to be going well. I wish he would have done that sooner. Thank you all for your replies.

Cheers
Kev