Water loss for double mash

[Wolfman1]

im working up an imperial stout recipe which is going to call for 11.5 kg of grain which is about 5 more than I’ve ever worked with in my 40 lt urn with BIAB. The spreadsheet pushes me over the top of my urn.
I’m going to do a double mash, so is my liquid lost to grains going to be the same as it would for a single mash and I could fit it all in?
My spreadsheet is calling for 35.14 litres strike water which leaves me 29.8 litres into the boil.

Isn’t grain absorption going to be the same irrespective of single or double mash?

Or should I just drop the water volumes to fit it all in the urn and then add some water as a sparge into a separate bucket and then combine again.


Thanks

 

[MHB]

What is your target OG, I'll have a play with some numbers.
Mark

 

[Wolfman1]

Cheers. It’s the diy dog paradox Jura.
1.128 and looking for about 21l into the fermenter.
I was thinking of splitting it into 4 different batches for secondary with different aging combinations.

 

[MHB]

Not half ambitious! Glad you are doing a long boil (~30% evaporation), working from your preboil numbers ~30L at 1.093 (23.3oP) I get the best result by doing two heavy mashes with half the malt. Then combining them for the boil.
Works out to 5.75kg mashed at 2.5:1, batch sparged with 1l/kg of grist (be patient, give the batch sparge at least 30 minutes), should get you fairly close.
From my finger counting you would need to be getting 66% efficiency accross the double mash and at those gravities I really cant see you hitting the targets. Even doing two mashes I think you will pull up a bit short on volume ~19L at EOB.

Double mashing is usually horrendously inefficient, in this case with a 40L urn I'd do the split mash.
Mark

 

[Wolfman1]

Thanks for that. Why not be ambitious? What’s the worst that can happen?

 

[Wolfman1]

Ok, just finished it. Ended up being a bit of a shambles and the shed looks like an oil tanker has run aground in it. I think Greenpeace are looking for penguins to clean up.
Ended up going for 9.5 kg in 30l but the mash was a disaster. I put it on last night thinking an overnight mash would help, but it didn’t. Without any recirc i think I ended up with 1.065 pre boil.
I put it on again and recirc with a jug and got almost up to 1.070 so stuck in a 0.5 kg of raw sugar and DME. I boiled for an extra hour and then with chocolate, cacao and coffee at flame out I ended up at 15l volume and OG which looks terrifying.

So far it tastes amazing from the sample. Good amount of coffee and the hops are just subtle but it’s mighty sweet.

 

[MHB]

looks like 1.104 or 26oP so your mass of extract from Me=V*SG*oP = 15*1.104*0.26 = 4.3056kg from 9.3kg of malt.
That includes the 0.5kg of Sugar and 0.455kg of Dex, so you got 4.03056-0.955 = 3.35kg of extract from malt
Say all base malt with a 76% CGAI would have a potential of 9.3*0.76 = 7.068kg, efficiency is like 47%.
Sort of what I meant by "horrendously inefficient"

Just looking at the mash, 9.5kg in 30L, that's a L:G of 3.158:1, applying the simple "First Runnings" calculator
oP (first runnings) = % GCAI/L:G+CGAI = 0.76/(3.158+0.76) = 19.4oP or 1.0776 and you should have 21.45L, boil that down to 15L and the OG would be 27.7oP or 1.111. that's without adding the Sugar and Dex, so yep something went awry in the mash.

I like making really big beer (>1.100) but they come with a bunch of unique challenges, I'm not convinced that double mashing is really the best answer.
Mark

 

[captain crumpet]

looks like 1.104 or 26oP so your mass of extract from Me=V*SG*oP = 15*1.104*0.26 = 4.3056kg from 9.3kg of malt.
That includes the 0.5kg of Sugar and 0.455kg of Dex, so you got 4.03056-0.955 = 3.35kg of extract from malt
Say all base malt with a 76% CGAI would have a potential of 9.3*0.76 = 7.068kg, efficiency is like 47%.
Sort of what I meant by "horrendously inefficient"

Just looking at the mash, 9.5kg in 30L, that's a L:G of 3.158:1, applying the simple "First Runnings" calculator
oP (first runnings) = % GCAI/L:G+CGAI = 0.76/(3.158+0.76) = 19.4oP or 1.0776 and you should have 21.45L, boil that down to 15L and the OG would be 27.7oP or 1.111. that's without adding the Sugar and Dex, so yep something went awry in the mash.

I like making really big beer (>1.100) but they come with a bunch of unique challenges, I'm not convinced that double mashing is really the best answer.
Mark

hey do you remener all of these formulas off the top of your head? i love reading through them every time. i feel like i rely on beersmith way too much

 

[Wolfman1]

It was pretty stressful, mainly because I’m virtual solo dad at the moment and it needed a lot more attention than I’m used to with BIAB & cubing but was an interesting challenge. Certainly the most rewarding beer I’ve done and I’m sure the fermenting will be just as challenging.
I think I should have stuck to a smaller batch and worked on the mash getting it first established and set on temperature rather then just mashing in and assuming it’s going to work the same as my normal 5kg grain bill.

 

[MHB]

hey do you remener all of these formulas off the top of your head? i love reading through them every time. i feel like i rely on beersmith way too much

Sure, part of the basic working tool kit of a brewer, but its really just a rearrangement of the standard mixing formula
Aa*Bb=Cc, in fact lots of the formula used in brewing are, probably why its called the Standard..... and I've been doing this for a long time some of it should have stuck.
I do agree a lot of brewers cant or wont do the basic maths, I find it really handy, when I have managed to make a really dumb choice - the numbers tell me and they never lie.

If you want to dig into the maths that supports brewing "The Handbook of Basic Brewing Calculations" is a great start, Steve at Brewman gets a bundle of 10 or so in from time to time - he sells them at cost (sometimes a small loss) or you can order one direct from the MBAA (have a look at the rest of the book list)
Mark

 

[chesl73]

You are only half way there. Fermentation is the key now. Make sure you pitch the right amount of yeast for that OG and it's all aerated. You also want to get a good an attenuation as possible as otherwise you'll end up with a sickly sweet beer.

 

[Wolfman1]

Update - fermentation was started this
Morning. Starter was a 2 half jars of cake from the last brew with 1272 and a litre starter on the kitchen bench for a couple of days.

Wort was tipped from the cube into the fermenter from a good height so all the conditions are as good as I can do.

Yeast was pitched at 9:30 and the airlock started at 12 so it’s got its skates on. Let’s see where it ends up in 3 weeks

 

[Wolfman1]

Gravity check at day 5 and it’s been a qualified success. Sg at 1.030 so it’s 9.7% and tastes every bit of it. If it can get to 1.020 I’d be a happy boy. It’s got 2 more weeks in primary and then 2 months with oak in secondary to smooth itself out.
The coffee and chocolate are running the show at the moment with it being a very thick sample. Given it’s still fermenting I’m not surprised as it’ll won’t be settling out much yet.

 

[Rocker1986]

I did something similar recently although not to quite as high an OG and not really an imperial stout, just a bigger version of my usual one with increased amounts of base malt and roasted barley. It's sitting in a second fermenter now and is almost finished going by yesterday's SG sample.

The grain bill was nearly 9kg, and I went the re-iterated mash route for it, doing 4.5kg of the base malt by itself for the first mash in the water, then the rest of it plus the specialty grains in the second mash in the wort from the first mash. I was also aiming for 21L but decided to increase the strike water by a couple of litres to 34L just in case and it worked well. The pre-boil SG was 1.0694 in around 30L, and after a 75 minute boil that increased to 1.0855, got the target 21L into the FV giving me around 66% brewhouse efficiency which I expected really, down from my usual 75-76%. Checking it yesterday after 5 days in the FV it had dropped to 1.024ish, with the estimated FG around 1.020-1. It'll be on tap next winter, but the sample I took yesterday tasted good, nice and roasty.

 

[MHB]

1272 is supposed to be able to go to 10%, that's a change of gravity (from ABV%=Change in gravity/7.5)
or 75 points (1.075). If your OG was around 1.104 (what it looks like in the picture in post #6), 104-75=29 or an FG of 1.029, so I cant see it going too much further.
If you are serious about making really big beers you might need to look at different yeast, I'm a fan of the good old Irish Ale 1084, will go to 12%, pretty easy to manage and I like its flavour profile, even more alcohol tolerant than Trappiest High Gravity - without the funk.
Mark