Huge boil volume question

Hello! I'm new to this forum but not entirely new to brewing. Me and my buddies have done a couple simple all grain batches already and they came out great.

Last week we did an all grain chocolate oatmeal stout with high ABV as one of the main goals, so we used 28lbs of grain. We got this from a recipe for a 6 gallon batch so we hardly altered it since we were trying for a +5 gallon batch. The recipe gave a specific amount of mash and sparge water, so we reduced it by less than a gallon to fit our brew pot. The boil volume it called for was a little over 8, so we reduced it to a little under 7.5 gallons. Even after the last drop of sparge water, the color was still opaque. After the boil, the OG we measured was NOT what we had hoped for- like 1.088 instead of 1.25. Beersmith said our efficiency was 46.3%.

Next time, I'd like to stick with the ~1.33qt/lb ratio for mashing and 2qt/lb for sparging but if we are going to use a lot of grain again, we'd have like +20 gallons of boil volume for a 5 gallon batch. At 9% evaporation, that's like a 6 hour boil to get it down to 5 gallons!

Here are my questions: With a lot of grain, should we use the ratio for mash water and sparge until the color is almost clear or use up to required minimum boil volume? If sparging until clear, the boil volume might be huge (like 20gal as mentioned) so is it harmful to boil for hours to get the target batch volume? Obviously at the end of the long boil, we'd maintain the hops schedule. And when I say sparge til clear, I mean either almost clear or when the meter reads something acceptably low.

I've always brewed my high gravity beers with a qts/lb ration of around .75. It works out great. Obviously, you'll have a lot of water in the mash, but some of it will be absorbed. Just add less sparge water if you have to. I hardly ever sparge until clear...even with my normal gravity beers. I add the amount of water I know I'll need to hit my pre-boil volume, and I usually end up with and efficiency around 80%.

Using .75, you don't have a problem with the water level being below the height of the grain bed?

With bigger beers, I still mash with 1.25 quarts per pound to convert the starches, but then may reduce the sparge volume and only sparge up to my boil volume, You give up some efficiency by doing that, but it's better than starting with an 11 gallon boil and boiling all day long!

I get about 75% efficiency on beers with a 1.065ish OG and about 68% on bigger beers, because I'm sparging less in the bigger beers. Once you know that, you can adjust the grain bill if needed to make up the difference.

Yooper said:

With bigger beers, I still mash with 1.25 quarts per pound to convert the starches, but then may reduce the sparge volume and only sparge up to my boil volume, You give up some efficiency by doing that, but it's better than starting with an 11 gallon boil and boiling all day long!

I get about 75% efficiency on beers with a 1.065ish OG and about 68% on bigger beers, because I'm sparging less in the bigger beers. Once you know that, you can adjust the grain bill if needed to make up the difference.

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In this case we used 1 qt/lb then brought it up to min required boil volume. I was really surprised by the 46.3% tho cause doing it this way seems to be the norm. But say I had all the time in the world and didn't care about spending the extra cheese to do a 6 hour boil, would a super long boil be harmful for the wort?

QuagmiresChin said:

Using .75, you don't have a problem with the water level being below the height of the grain bed?

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I had no problems. It was a nice arm workout trying to get the grains all stirred up, though.

No a long boil won't be harmful, beyond potential scorching and copious propane waste. Your problem, I'll bet dollars to donuts, is that you did not get full conversion in your mash. You should do a iodine test for conversion. Sparging allows you to rinse otherwise wasted sugar from the mash, but even no-sparge brewers are getting better than 50% efficiency. It may take some brewers 20 minutes to get full conversion; it takes me 60-90 minutes every time.

Ya I've been reading a lot on just the mash process since we brewed. We had a few mistakes here and there like the temps were a couple degrees higher than the target for mashing and rinsing. For mashing, I stirred it around for 5-10 minutes and got it to the target, but rinsing was at 171 instead of 168. We mashed 90 minutes on the dot but mashed out wayyyyyyyyyy too fast. We're definitely going to have a slow leak rate going next time.

If you mashed ninety minutes you should be good, an iodine test gives you certainty. I don't know what you mean by mashing out too fast. Sparging at 171f vs 168f is just fine. If I do a mash out, I do it after I know my mash is fully converted. I raise the temp to 168f with a decoction and then sparge immediately at 170f + or -. A lot of folks skip the mash out with fine results.
If you have 47% efficiency with a 90min mash, I'd guess you have something else going on like channeling? Pretty hard to say.There is a sticky thread at the top of the page which addresses low efficiency problems. It is likely to help you out. You might want try a batch sparge to simplify things. Dennybrew.com is a good resource for batch sparging.
Don't be discouraged.

Ya I read the stickies before I posted this and it answered most of my questions. By mashing out I mean draining the wort from the cooler before rinsing (if I used the term correctly haha). Thanks for the help guys

QuagmiresChin said:

Ya I read the stickies before I posted this and it answered most of my questions. By mashing out I mean draining the wort from the cooler before rinsing (if I used the term correctly haha). Thanks for the help guys

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Mashing out means adding near-boiling water to bring the grain bed to 168-170 degrees.

Draining the wort is just, well, draining the wort. Lautering is the act of separating the wort from the grain, so you kinda sorta can call it lautering.

QuagmiresChin said:

Here are my questions: With a lot of grain, should we use the ratio for mash water and sparge until the color is almost clear or use up to required minimum boil volume? If sparging until clear, the boil volume might be huge (like 20gal as mentioned) so is it harmful to boil for hours to get the target batch volume? Obviously at the end of the long boil, we'd maintain the hops schedule. And when I say sparge til clear, I mean either almost clear or when the meter reads something acceptably low.

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I can't see how that would effect effeciency much....if you're using up propane that much, you'd be spending more on propane then extra grain anyway. Sounds like it was the usual suspects that got you: amount of crush, hitting mash temps, effectiveness of sparging. Especially with high gravity beers, I tend to go for my usual boil volume. With 5.5 gallon batches, I get around 85%...with 11 gallons it's around 75%.

Yooper said:

Mashing out means adding near-boiling water to bring the grain bed to 168-170 degrees.

Draining the wort is just, well, draining the wort. Lautering is the act of separating the wort from the grain, so you kinda sorta can call it lautering.

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Ahh I see. And for the overall process, we'll be more meticulous about it next time.

I didn't see at the begining, are you fly sparging or batch sparging? With high grav brews, I have had much better success with striking .75 qt/lb and doing a 3x batch sparge. With the sparge volumes being an approx .25, .50, .25. With each sparge keeping the grain bed at 165-170. The last part being important because I have a keggle-tun, and sparging without an insulation blanket has heat loss.

bowiefan said:

I didn't see at the begining, are you fly sparging or batch sparging? With high grav brews, I have had much better success with striking .75 qt/lb and doing a 3x batch sparge. With the sparge volumes being an approx .25, .50, .25. With each sparge keeping the grain bed at 165-170. The last part being important because I have a keggle-tun, and sparging without an insulation blanket has heat loss.

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Batch sparge with a little more than 3 gallons to bring the total up to the minimum boil volume. We're using a cooler with a one of those wire fabric tubes attached to the spout at the bottom with another tube to direct where it'll go. The only way we can control the output is by raising the tube higher to about the level of water in the cooler. We'll have to try fly sparging next time or just slow everything down. I already want to make another batch just to get it right haha

QuagmiresChin said:

Batch sparge with a little more than 3 gallons to bring the total up to the minimum boil volume. We're using a cooler with a one of those wire fabric tubes attached to the spout at the bottom with another tube to direct where it'll go. The only way we can control the output is by raising the tube higher to about the level of water in the cooler. We'll have to try fly sparging next time or just slow everything down. I already want to make another batch just to get it right haha

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Just for clarification, when batch sparging, you want your outflow to be fast. For your high grav brew I would do the following: calculate at .75 qt/lb strike water (5.5gal). Subtract your loss volume (somewhere around 2.5-3gal)and calculate your sparge water(4-4.5 gal) and break the sparge out to 2gal 1st sparge+ 2.5 gal 2nd sparge, stirring thoroughly and resting 15 min after each addition. I would also think about running the grains through the mill twice to improve conversion efficiency due to the lower volume of water in the mash. Also, quality time with the mash paddle, dough balls will be able to hide easily in that much grain.

bowiefan said:

Just for clarification, when batch sparging, you want your outflow to be fast. For your high grav brew I would do the following: calculate at .75 qt/lb strike water (5.5gal). Subtract your loss volume (somewhere around 2.5-3gal)and calculate your sparge water(4-4.5 gal) and break the sparge out to 2gal 1st sparge+ 2.5 gal 2nd sparge, stirring thoroughly and resting 15 min after each addition. I would also think about running the grains through the mill twice to improve conversion efficiency due to the lower volume of water in the mash. Also, quality time with the mash paddle, dough balls will be able to hide easily in that much grain.

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Why .75 quarts/pound? Do you have a pH issue? That's a terribly thick mash!

Yooper said:

Why .75 quarts/pound? Do you have a pH issue? That's a terribly thick mash!

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I don't, but I don't know about the OP and his terrible efficiency. This way it address possible water issues, poorly modified malt, poor crush, channeling durring sparging and under sparging and keeps him from having to boil 12 gallons down to 6. If I was brewing it myself, I would do it a bit different, but I was trying to stay within his stated preferences and hit as many possible issues as I could.

i'm pretty sure that you won't be able to get a 1.250 OG no matter how much grain you use. i guess if you try just sugar, that might do it...

I fly sparge and my procedure is to sparge very slowly until I have collected the desired pre-boil volume. Normally, the runoff near the end contains very little sugar. IMO, it's not worth collecting additional wort and extending the boil.

Here's how to improve your efficiency when fly sparging. Do a mash out if you can (ie bring the grain bed up to 168-170F. Stir the grain bed thoroughly. Vorlaugh until the wort runs free of particulates. Don't worry if the wort is not crystal clear. Sparge very slowly at about 1 qt/minute or so. Stop the sparge when you have collected your pre-boil volume or when the runoff no longer tastes noticeably sweet. (or when the gravity drops below 1.010 or so).

IMO, the key to improved efficiency is stirring the grain bed well immediately prior to beginning the sparge and sparging slowly. Doing a mash out also helps, but mainly it's the stirring.