What ABV should this hit, getting varied results?

[ChiknNutz]

I have created an Imperial Stout recipe and am confused about the predicted ABV. I've entered this into three different calculators and all yield quite varied results ranging from 9.3% to 12.3%. To enhance mouthfeel, I plan to mash at a about 154. I'd like it to be reasonably close to the original that I am trying to emulate which is 11.3%. If they were all within like a 1/2% then I wouldn't worry too much but a variation of 3% seems like too much. What do I trust?

18# - 2-Row
2# - Chocolate Malt
2# - Caramel/Crystal 80
1# - Flaked Oats
0.5# - Black Patent Malt
0.5# - Roasted Barley
1# - Maltodextrin
- - - - -
25# total

 

[mullet6577]

Brewersfriend puts that right about where you're trying to get (used 5.5 gallon batch, 75% efficiency since those weren't mentioned in the original post)

 

[bailey mountain brewer]

gonna depend on yeast as well and assume your doing a starter for that high ABV target. unless dry yeast of course. if your fermentation stalls at say 1.040 then your at 10.9%

 

[ChiknNutz]

Sorry, this is for a 5.5G batch and planning to use two packs of US-05

 

[doug293cz]

What's your target pre-boil volume, target boil off (total), sparge or no-sparge, sparge process if no-sparge, bag squeeze or no-squeeze? These items will all affect your lauter efficiency, which is one of the two components of mash efficiency. With this data we can fairly accurately predict what your mash efficiency and OG will be. ABV will then depend on where your FG ends up.

Brew on

 

[ChiknNutz]

Strike volume of 9.21G. 60 minute boil, Pre-boil: 7.35G, post-boil: 6.1G, no sparge (full volume BIAB), bag squeeze (both grain and hop bags). Estimated mash efficiency of 72%, mash for 75 minutes @ at 152 degrees. Using BrewCipher I get an ABV of 9.8%, with others I see a much higher predicted ABV. Predicted OG is 1.090.

Since I posted this, I have been tweaking the recipe, thinking of bumping up to 20# of 2-row to get a bit closer to intended ABV (10.7%). Predicted OG here is 1.097. Strike volume goes up to 9.37G. Not that it matters for this exercise, but am thinking about switching out the MD for Lactose as the original is a bit sweet.

At the end of the day, the ABV isn't as important as knowing what to expect...that is the real goal here.

 

[doug293cz]

Strike volume of 9.21G. 60 minute boil, Pre-boil: 7.35G, post-boil: 6.1G, no sparge (full volume BIAB), bag squeeze (both grain and hop bags). Estimated mash efficiency of 72%, mash for 75 minutes @ at 152 degrees. Using BrewCipher I get an ABV of 9.8%, with others I see a much higher predicted ABV. Predicted OG is 1.090.

Since I posted this, I have been tweaking the recipe, thinking of bumping up to 20# of 2-row to get a bit closer to intended ABV (10.7%). Predicted OG here is 1.097. Strike volume goes up to 9.37G. Not that it matters for this exercise, but am thinking about switching out the MD for Lactose as the original is a bit sweet.

At the end of the day, the ABV isn't as important as knowing what to expect...that is the real goal here.

With your original recipe and other parameters, your best possible mash efficiency is 69%, and that only if you get 100% conversion. I get your pre-boil SG at 1.080 and your OG at 1.096. Assuming FG of 1.030 I get an ABV of 8.66% (std formula) or 9.59% (alt formula) using BrewersFriend calculator,

If you up the 2 row to 20 lb and leave everything else the same (except increasing strike volume to make up for additional grain absorption) then I get max mash efficiency at 67.5%, pre-boil SG at 1.084, and OG at 1.101 - 1.102. ABV using same FG is 9.38% or 10.48%.

If your conversion efficiency in the mash is less than 100%, the all the calculated values will be lower.

Brew on

 

[dmtaylor]

I agree with @doug293cz . And you're not going to be able to achieve 100% efficiency so the numbers WILL be lower.

With big beers, your efficiency is limited by the amount of water you use and the length of the boil. By my calculations and experience, with your specific recipe, for standard water amounts and a 60-minute boil, your efficiency will max out at about 62%. You can fix this easily, not by adding a lot more grain, but by adding another gallon or more of water to your mash (traditionally non-BIAB, this would be added in the "sparge" rinse step), then plan to boil not just for 60 minutes but for 120 minutes or longer. Another way to think about this: You need to gather more sugars, then concentrate them down more.

Otherwise, with your process as per the original post, the highest OG you can realistically achieve will be about 1.098 and 9.9% ABV by my calcs based on much experience. And this is with an excellent crush and squeeze, etc.

Recommendation: Use more water, at least an extra gallon, and boil the bejeezus out of it for at least 2 hours. That's the only way you will achieve your goal.

OR..... take the easy way out and just add a pound of extract in the last few minutes of the boil. That's easy peasy and effective as well. It depends if you care about this being all-grain vs. almost all-grain with just a little extract. I've done that too, it works really well.

 

[ChiknNutz]

Thanks for the feedback! I also planned to mash for 75 minutes vs 60 which will boost it a little. I had not yet considered more water and a longer boil, but it makes sense to me.