Brewing an Imperial Stout today, using London Ale yeast. The website says it is good up to 11% ABV.
Never made a high gravity beer with this before. Mine came in at 1.093, or 22.2 Brix.
What has your experience been?
Looks like my efficiency is off a bit, as the recipe calculator said OG of 1.120.
When I make big beers my efficiency always goes down 10-15%. I pay less attention to what the yeast manufacturer states as the max alcohol tolerance and more to what the wort composition is. The more Crystal and Roasted grains the less attenuation.
THIS. Yeast attenuation rating is for comparing one yeast to another using a standard wort. It doesn’t necessarily reflect that attenuation you can expect. Wort composition is the main factor in attenuation.
Usually a reasonable estimate for most yeasts and recipes: Gravity points divided by 4. That’s specific gravity but ignoring the 1.0 in front.
So, for 1.093, that’s 93 / 4 = 23 which is 1.023.
However Denny is correct, the real number is very dependent on yeast strain and recipe, so if we have that, including mash times and temperatures, then we can refine the estimate further.
P.S. Another very rough guideline: If the OG is 1.093, then you should end up with roughly 9.3% ABV, plus or minus a few tenths. This works for many yeasts and recipes, but again… it depends.
Rough top of the head math is that you’ve got around 13% low fermentables. I wouldn’t expect it to finish any lower than the 1.023 Dave predicted. Which wouldn’t be bad. But like I said, it’s only a guess.
I agree with the ballpark numbers from Denny and Dave. One other crucial factor is the yeast pitch. Fresh, big, and healthy will get you a lot closer to the mid to low 1.020s FG
In my experience, pitch rate is important to minimize lag time and get to the goal faster, while minimizing off-flavors… but should not affect attenuation / FG, with enough patience.
Thanks for your input.
This recipe is taken from North Coast RIS, but a lot more base malt was added. About 8 lbs total extra base malt, 4 lbs Pale, 4 lbs Munich. My goal was to hit north of 10% ABV. But, we can live with 9.3% +/-.
The yeast is fresh, being harvested about a month ago from an English Porter. Got it going yesterday, with added fresh wort, and today with more wort. It looks very good, and active. About 1/2 gallon slurry in a 6 gallon batch. And the aroma from this yeast is to die for!
edit: Yes, I know…another example of over-pitching. But it works for me!
Not sure if this is an indicator or not, but within 3 hours of pitching the yeast, there are signs of healthy activity. C02 discharging from my blow-off tube! I think the yeast is healthy, and sufficient!
I have brewed a nearly identical recipe (but no special B) and have gotten 1.087 ->1.023, 1.092->1.024, 1.093->1.023, 1.092->1.029. I did a single rest at 152 F. All were stunningly delicious!
It was good right away but did improve with age. I just noticed two important differences: I made a 5 gallon batch with 10 lbs of pale malt and the same amounts of specialty malts as you (but I didn’t use Special B) so my flavors were stronger. I also used WLP028 Scottish Ale Yeast because I like to use it for stouts.