Pitching calc confusion

[einzack]

Hi,
After using exactly 1 packet of re-hydrated dry yeast for the first dozen or so extract + steeping grain brews I've done, I decided to use a yeast pitching calculator for a recent batch.
It was a Liquorice Stout, SG of 1.065. I was using Nottingham yeast, which I've used before. Headed over to Mr Malty and got told to use 15g of yeast. Sorted. At the last minute I found a pitching calculator on the Lallemend website (company who make Nottingham Yeast), so I popped the same variables into that calculator and it tells me to use 21g of yeast!
What? I was rather confused at this point. On the spur of the moment I decided to go with the Lallemend amount as I thought surely, they'd know what they're talking about right?
Well, not so sure upon reflection, and waking up to this after less than 36 hours....
pic was taken after I had put the lid back on cause it had popped it right off.

So I cleaned and sterilised the airlock and kept going. It's being bottled tomorrow, and all seems ok at this point, so I'm not particularly concerned about contamination etc, but why would the official yeast-maker calculator be so far off? Does it assume that I'm just pitching the dry yeast straight into the fermenter without re-hydrating? The website doesn't say anything about that, but I do wonder if that's the issue.

 

[thehaze]

I do not think that the " official " calculator was off. I think they calculate starting from the cell count they provide for their yeasts, without taking into account third party calculators or other third party info. From what I know, nobody has actually officially counted the exact number of yeast cells in dry yeast, so everything " we " know is based upon years of experience.

The yeast you are using is pretty aggresive and most likely requires head space in the fermenter. It is not unusual...

But for a beer with an OG of 1.065 I would probably use 1, maybe 1.3 packs of yeast without any rehydration. But I think you can easily get away with only one.

For beers up to 1.080-1.085ish I go with two full packs. This is for Fermentis yeast. I am not sure Lallemand has the same cell count per gram yeast, but it should be close.

 

[Pkrd]

Looks like a good healthy ferment, only thing wrong is the lack of blowoff tube.

 

[einzack]

I guess we all have compromises in our setups...well, maybe not everyone, but a blow-off valve is not something I've considered I needed before this particular brew...

I've brewed most of my beer-experience in the 1.060-1.065 range, several with Nottingham, but all previous were with 1 single packet, and none reacted quite like this one. The one before this one was 1.066 with US-05 for example.
And I'm certainly not suggesting this isn't healthy, although it is obviously too energetic for my setup!

My post was more about the difference between the two calculators. I assume that this variance isn't as apparent at the bottom-end of pitching predictions, where it could have more significant consequences.

For my latest brew, a Dandelion Stout, I followed the Mr Malty calculator for a 1.063 using S-04, giving 13g and the response was more in line with what I've seen before.

I guess, all that really matters is how it drinks, and I'll find that out in a few weeks.

Thanks for the responses...