I want do a step infusion using an insulated cooler as a mashtun. I have found calculators that tell me how much water to add to ensure I hit the target temp of the second rest (add 7.7 quarts of boiling water to raise the temp from 148 to 168) but they don’t adjust the initial water volume to account for the additional water to raise the temperature.
How do I know how to adjust the amount of water used for the first rest temperature so I don’t end up with too much/diluted wort? Do I just take the amount of water listed in the recipe (15 quarts for example) and deduct the amount I will need to add for the infusion (15 - 7.7 = 7.3 quarts ). This doesn’t sound right. I’m afraid if I do this the mash will be too thick and get stuck.
Thank you all in advance
What you want to do is lower the initial strike water to grain ratio and go from there. For example if you start with a lower ratio, say 1:1, you would need 10qts at roughly 170° to 10lbs of grain if shooting for 152° rest. If you wanted to raise it to 168° you would add roughly 4.5qts of boiling water. Your water:grain ratio is now 1.44:1.
To see what will fit in your MT check this out
I took advantage of a sale before Christmas and picked up WootStout. Just want to confirm on ratios. I typically mash 1.5 - 1.6 qt/lb depending on the recipe. This one has 21.12 lbs of grain. I batch sparge in a cooler so I will have to do an infusion to raise the temp after the initial rest at 122 for 30 mins. So if I’m mathing right, if I drop the initial ratio to 1 qt/gal then I would need roughly 10.25 qts of boiling water to reach mash temp of 148. I typically lose max 1 degree over the course of a standard hour mash, this is a full 120 min mash so should I try to bump that up to 150ish to be safe?
I assume grain absorption of .12 gal/lb based on my typical volumes. Absorption should be just over 2.5 qts. This plan of attack should yield me just shy of 1.4 qt/gal total for the first ruhnings. I factor 1 qt of dead space for my cooler. I should be able to get just under 7 gallons out of the first runnings. Then I would batch sparge with around 2 gallons and boil down to my starting volume for a 90 minute boil.
The question is, this is a really big beer, the biggest I’ve ever attempted AG. Should I reduce my initial volume below 1 qt/gal and increase my sparge at the end to get closer to even volumes for both runnings or try to run it through this way? Any tips on brewing bigger beers I should be aware of?
So I brewed yesterday and pulled it off in the end fairly well. I did my initial infusion with .9 qts/lb of grain (4.75 gal) for the 30 min rest and added just shy of 2.5 gallons of boiling water to raise my temp, but it only got to 142 so I added another gallon of boiling water and got it up to 146 which I figured was close enough to 148 so I let it ride. I had put a total of 8.25 gallons of water in so I was expecting around 5ish gallons from the first runnings and heated up 2.75 gal for my sparge. . .
First runnings stopped just over 3 gallons. . .wtf?
Ok, I’ll add another gallon or so to the tun after I’ve added my sparge water and sparge more, problem solved. . .
Second runnings got to 7 no problem. . .and kept coming. . .and coming . . .I have a 10 gallon kettle, I stopped the runoff at 9 gallons. 
Apparently I had a stuck mash that I wasn’t aware of and when I stirred it up for the batch sparge, I was able to loosen it up enough that it all came out. So now with more than 9 gallons total, I boiled down to 7 gallons and then started my 90 min boil. As I boiled some off, I ran more out of the tun just to make sure I got all the sparge water out.
Overall, this turned into an 8 hour brewday, but the good news is the target OG was 1.109 and I got 1.10 so I am very happy with those results. I pitched 2 packs of US-05 and now I get to wait for 9 months. Lesson learned, when you are 2 gallons short of your target for your first runnings, you probably have an issue that needs to be addressed. 
Rad
