Mash and Sparge Calculations (yes again)

[jayhoz]

I apologize up front for this question. I know it has been asked before, but I don't quite get it.

I am brewing an all grain version of Denny's Rye IPA (http://hbd.org/clubs/cascade/public_html/recipes/recipes.html)

Total grain bill is 16.25 lbs and it calls for a single infusion mash at a water to grain ratio of 1.33 and mash temp of 153.

I am pretty confident on the dough in details. Assuming a grain temp of 72 and "warmed up" mash tun I will need to add 21.6 quarts of water at a temperature of 165. I estimate that I will lose 1.95 gal of water to grain absorption, and 0.25gal to mash tun dead space. This puts my first runnings at 19.4 quarts.

I would like to do two batch sparges of equal volume to try to rinse out as much of the sugars as possible.

I will lose 0.5 gal to trub left in the boil kettle and shrinkage, and 1.5 gal to boil off (90 min). In order to get my desired 5.5 gal into the fermenter I will need a total of 7.5 gal of wort into the boil kettle. This allows for 10.6 quarts of sparge water.

1st sparge = 5.3 quarts at 183 degrees (target mash temp is 168)
2nd sparge = 5.3 quarts at 168 degrees (maintain 168 mash temp).

My questions are:
1) Are the calcs correct?
2) This seems like way too little sparge water. What is the ideal amount of sparge water?
3) How should I get closer to the ideal sparge water amount? Thicker mash, longer boil, etc? I don't like the idea of the longer boil, but I'll do it if I have to

 

[Bobby_M]

It seems like a small amount of water but you have to realize that the grain is thoroughly wetted when you infuse. It becomes a lot more fluid than you'd expect once you stir.

I actually think 1.3 is a little thinner than you'd need to go so you could mash with 20qts (5 gal) and then do two sparges at 6 qts each (1.5g).

Are you 100% sure about your grain absorbtion and deadspace? If not, measure your first runnings exactly and make up for any difference real time by sparging more.

 

[Yooper]

Losing almost 2 gallons to grain absorption doesn't seem possible to me. You'll probably have more first runnings than you're expecting. But then, you say you're expecting 19.4 quarts out of that. That's 2.22 quarts, not gallons, that you're expecting to lose. I think this is where your math doesn't make sense to me, but I'm certainly no math whiz, so don't worry about what I think!

I mash at 1.25 quarts per pound usually, and that's a nice mash. I'd mash in with 20 quarts, as Bobby said, and expect sparge with about 2.25 gallons total. You can definitely sparge with more, but then you'd boil longer.

 

[Got Trub?]

Mash volume is 21.6 quarts - grain absorption (7.8q) - dead space (1q) = 12.8q

You want 7.5g (30q final volume) so you need to add 2.2q boiling water to your mash when it is done to bring up your first sparge (1st runnings) to 15q and as close to 170F as you can get. Your second sparge would then be with 15q of 170F water. Your recipe has alot of grain and your efficiency is going to suffer. You could increase your final volume and boil longer if you want to improve it.

 

[jayhoz]

Losing almost 2 gallons to grain absorption doesn't seem possible to me. You'll probably have more first runnings than you're expecting. But then, you say you're expecting 19.4 quarts out of that. That's 2.22 quarts, not gallons, that you're expecting to lose. I think this is where your math doesn't make sense to me, but I'm certainly no math whiz, so don't worry about what I think!

I mash at 1.25 quarts per pound usually, and that's a nice mash. I'd mash in with 20 quarts, as Bobby said, and expect sparge with about 2.25 gallons total. You can definitely sparge with more, but then you'd boil longer.

The 2 gal number comes right from beersmith. They calculate 0.12 gallons per lb of grain.

You are right. I mixed my gallons and quarts numbers. The corrected calculations are:

First runnings: 21.6 quarts (dough in) - 7.8 quarts (grain absorption) - 1 quart (mash tun dead space) = 12.8 quarts

Sparge Water: 30 quarts (desired wort to kettle) - 12.8 quarts = 17.2 quarts or 4.3 gallons

I prefer to do a first running followed by two sparges. I feel that this washes out the sugars better than a mash out and one sparge.

 

[Bobby_M]

Losing almost 2 gallons to grain absorption doesn't seem possible to me. You'll probably have more first runnings than you're expecting. .

Every system is different. Check out my numbers on a simple 9lb grist.

Infused 2.75g (11qts at 1.2qt/lb)
Mash out infusion, 2.5g at 195, settled at 164F. (that's a total of 5.25g in the MLT)
Vorlauf, drain 4 gallons.

I lost at least 1.25gallons (5qts) in 9 lbs of grain. It's actually a lot of deadspace I would assume because I'm using a wide rectangular cooler. You have less of that issue in a taller, smaller footprint MLT.

So, I lose about 1/2qt per pound to absorbtion/deadspace. I'm sure I can isolate the deadspace by comparing against my 10 gallon batches but I don't have those numbers here at work.

 

[ebeer]

FWIW I have a batch sparge calculator on my website. Hope it's of some use.

http://onebeer.net/batchspargecalc.shtml

Here's what I get for your numbers:


Total grain: 16.25(lbs)

Total wort pre-boil: 7.5(gal)

Mash water ratio: 1.33(qt per lb)

Grain absorption: .125 (gal per lb)

Mash/Lauter deadspace: .25(gal)

Mash water: 21.54(qt) 5.39(gal)

Grain absorption: 2.025(gal)

Mash infusion: .638(gal)

1st runoff: 3.75(gal)

2nd addition/runoff: 3.75(g)

Total water: 7.5(gal)

 

[davarm]

FWIW I have a batch sparge calculator on my website. Hope it's of some use.

http://onebeer.net/batchspargecalc.shtml

Very nice calc tool. Thanks for sharing!