Compensating for boil-off volume

I have a 30-qt turkey fryer kettle and find that I'm a little low on my batch volume towards the end of the boil. So lately I've been using extra the runnings from my sparge, saving it, and adding it towards the end of the boil. This has two effects: (1) brings my volume up to 5.5-6 gallons so I have a full 5 gallons after racking off trub in the primary and (2) brings my OG up a couple points which I've been tending to miss. I'm just starting with the all-grain and thought this was a brilliant idea until I started thinking of why we do 60 minute boils. Is there any reason this could be bad? I bring the wort back to a boil before chilling to make sure there's no bugs left. Also... should the "downtime" while the wort isn't boiling not be included in the total boil time?

A way to do this is to take a little extra from the mash as you describe, put this in a pot and bring to the boil on your stove top. 10 minute boil should be fine and then add back into your main batch 10-15 minutes before the end of the 60 minute boil.

Doing it this way will make sure that it gets a good boil to drive off any nasties and then by adding it back in when it has just been boiled means that you will not effect the boil of your main batch.

JNish said:

I have a 30-qt turkey fryer kettle and find that I'm a little low on my batch volume towards the end of the boil. So lately I've been using extra the runnings from my sparge, saving it, and adding it towards the end of the boil. This has two effects: (1) brings my volume up to 5.5-6 gallons so I have a full 5 gallons after racking off trub in the primary and (2) brings my OG up a couple points which I've been tending to miss. I'm just starting with the all-grain and thought this was a brilliant idea until I started thinking of why we do 60 minute boils. Is there any reason this could be bad? I bring the wort back to a boil before chilling to make sure there's no bugs left. Also... should the "downtime" while the wort isn't boiling not be included in the total boil time?

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To compensate for boil off volume, just watch what you're boiling off after a few times and there you go. Add that to your recipe when you do it in the first place. I started brewing in doors, in my kitchen, and I was boiling off about a gallon an hour. I had no idea it would be any different when I moved outside, on a big ass burner. After overshooting my post boil gravity, I realized I boiled off "too much". I now boil off about 1.5 gallons an hour, outside, so I take that in to account to my pre-boil volume.

Maybe I'm missing something, but I don't know how your OG could go up with adding saved up runnings. Even if you collect all of your wort after sparging into one big bucket and only boil up 5 gallons of it and that comes to 4.5 gallons of 1.056 wort and you add 1 gallon of 1.044 (~pre boil gravity), you're gravity is going to be 1.054. Still less than what you've boiled down to.

In a 30 qt pot (7.5 gallons), I've been able to get 7 gallons (for 90 minute boils) to boil on my stove. Yes, I have to watch it for boil overs, but I've been able to do it. Either way, you shouldn't be boiling off 1.5 to 2 gallons an hour inside on a stove. I have one of those power plus burners, and I'm only burning off a gallon an hour in there. So you should be able to do a 6 to 6.5 gallon pre boil volume in your recipe and should be ok.

If you're brewing outside and you're boiling off 2 gallons an hour (crazy, but I've heard of it), lower the fire power on that rocket ship that's cooking your wort.

What I did was, I took the same pot and boiled 6 gallons of water inside, and 6 gallons of water outside. That gave me my different boil rates. This might change with the sugary wort and other factors like humidity, but that's going to get you real close. Once you figure out your boil off rate, you'll be able to formulate recipes better.

I can see three concerns with what you mentioned.
1) You need to boil to kill the 'yeasties' as mentioned
2) You need to boil to drive off the DMS from lightly kilned malt. This is why pilsner malt based wort's are often boiled 90 minutes. (I always do 90, personally)
3) You want to make sure that the "extra" sparge water you are collecting is not causing you to extract excess tannins from the hulls. If I remember correctly, a general rule is to stop extracting the wort when it is around 1.015 OG.

I would recommend boiling that extra liquid the full 60 minutes, making sure that the liquid you collect is still coming out the MLT over 1.015. Of course, the ideal scenario would be to measure how much you add and then compensate your recipe for it the next time.

ajwillys said:

, a general rule is to stop extracting the wort when it is around 1.015 OG.

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I've heard you stop at 1.010.

Just add water. Take a pre-boil reading so you have a good estimate what your OG will be. Then be prepared to add water or boil longer to hit your gravity. Adding unboiled wort is not a great idea, especially if you care about clarity. On my beers, I almost shoot for a little under my volume, it's much easier to quickly add some distilled bottled water to top up to my target volume then to keep boiling. Especially when late hop additions will be involved.

janzik said:

I had no idea it would be any different when I moved outside, on a big ass burner. After overshooting my post boil gravity, I realized I boiled off "too much". I now boil off about 1.5 gallons an hour, outside, so I take that in to account to my pre-boil volume.

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Yep, outdoors I boil off 1.5-2 gallons. I adjust pre-boil volume to get my target pre-boil gravity, and then save the dead space water from my HLT and top off at the end of the boil if needed (usually off by 1 L or less at the end for 13-15 gallon batches)

When my volumes in the past were under 5 gal prior to aerating and pitching I have added both water that I boiled and cooled, as well as bottled distilled water (wiping the spout of the water bottle with StarSan very thoroughly). Both worked with zero negative effects. But, nowadays I just do a better job of understanding how my brew process works (i.e., how much boil off I get on a consistent basis). I boil off between 1.25 and 1.5 gallons and lose another .25 gallons or so to trub.

johnnybrew said:

When my volumes in the past were under 5 gal prior to aerating and pitching I have added both water that I boiled and cooled, as well as bottled distilled water (wiping the spout of the water bottle with StarSan very thoroughly). Both worked with zero negative effects. But, nowadays I just do a better job of understanding how my brew process works (i.e., how much boil off I get on a consistent basis). I boil off between 1.25 and 1.5 gallons and lose another .25 gallons or so to trub.

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Even then you can be a couple points off your target. Brewing outside in the winter my boil-off rate is higher because it takes longer to reach boiling and the dry air is more receptive.

To say you're close enough is one thing, but to say you have reached the point of enlightenment and ALWAYS hit your volumes and gravities dead on without adjustment and I'm going to call BS.

Randar said:

To say you're close enough is one thing, but to say you have reached the point of enlightenment and ALWAYS hit your volumes and gravities dead on without adjustment and I'm going to call BS.

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I'm glad you said it because I am never 'dead on'. With experience I get closer, but either adjust or live with the small margin of error. If I nail it every now and again, cool for me. But, it doesn't keep me up at night not having exact volumes or gravities. I have a crisp $1 bill (yeah, I am cheap!) for anyone who can taste a beer and accurately rattle off gravities and volumes of the beer during the brew process.

It is not difficult to hit numbers and and volumes consistently with a system. You use the same equipment and process each time, with notes you learn your system. It will be have the same.

You have the right idea. Your boil kettle size is limiting you from what would normally be a larger initial preboil volume. Many people cut the sparge volume shorter to make up for it and therefore lose a few efficiency points. Sparge about 3/4 gallon more and add it over the course of the boil making sure the last addition is boiled at least 15 minutes. You'll find that you can add a bulk of it just after the first major hot break.

We boil for 60 minutes mostly due to the threshold of bittering hop utilization. Along with that, all grain brewers increase efficiency by concentrating wort. After 60 minutes, you're not saving money on hops so any gains in efficiency are quickly offset by energy costs.

You can get by with a 30 minute boil if you double your bittering hop addition.

Bobby_M said:

You have the right idea. Your boil kettle size is limiting you from what would normally be a larger initial preboil volume......

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.... so I use two pots. It sounds like we have the same size turkey fryer pot. I also use about a 3 gallon stainless steel pot and do two boils. I still get to do a 90 minute boil and end up with 6 gallons. When it all fits in one pot, it is chill time.

Wow, thanks for all the great comments! That's a great idea to boil the extra on the stove. Whenever I add to the wort, the temperature drops and it takes about 5-10 minutes to come back up to temperature. I haven't been including this extra non-boil time to my total boil time. I suppose the late hop additions will suffer because of this, but otherwise boiling longer is fine. Easy solution is to add boiling hot additions to the boiling wort.

The reason I don't just compensate by using a larger initial volume is that I don't like to fill my kettle to the top like janzik. Like he said, I'd need to add at least 7 gallons. I've had too many boil overs to make this fun. Also, I'm a newbie to all-grain (I'm only on my 3rd AG batch) so I'm still figuring out the process, changing a couple things, and tracking my efficiency and boil-off volumes. It might be that I don't need to add too much to the initial volume since I ended up with 6 gallons on my last batch. We'll see.

Janzik, the OG I'm referring to going up is referring to the gravity I would have if I add water instead. Say I do the sparge and take my reading it comes out to be 1.060 for 6.5 gallons in the kettle. I have a 1/2 gallon extra runnings at say 1.020 so I save those. After 60 minutes of boil my volume is down to 5 gallons, my gravity reading should be 1.078. If I add 1/2 gallon of water, that gravity drops to 1.071. If I add 1/2 gallon of 1.020 wort, that gravity drops to 1.073 instead. So I gain 2 points by adding extra sparge runnings instead of water.

Anyways, this will probably be moot soon as I figure out how much boil-off to expect and come to a stable efficiency. I suppose I could watch the boil with my hand on the regulator and fill up to near the top. I think I've been averaging around 1.5 gallon loss, so that would be a 7 gallon boil in a 7.5 gallon kettle.

Thanks for all the help!

JNish said:

The reason I don't just compensate by using a larger initial volume is that I don't like to fill my kettle to the top like janzik. Like he said, I'd need to add at least 7 gallons. I've had too many boil overs to make this fun. Also, I'm a newbie to all-grain (I'm only on my 3rd AG batch) so I'm still figuring out the process, changing a couple things, and tracking my efficiency and boil-off volumes. It might be that I don't need to add too much to the initial volume since I ended up with 6 gallons on my last batch. We'll see.

Anyways, this will probably be moot soon as I figure out how much boil-off to expect and come to a stable efficiency. I suppose I could watch the boil with my hand on the regulator and fill up to near the top. I think I've been averaging around 1.5 gallon loss, so that would be a 7 gallon boil in a 7.5 gallon kettle.

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Just to note, inside I was able to get away with 7 gallon boils in that pot, but not outside. The power of that burner was too strong, even with turning it down. Now I just use a keggle, even for 5-6 gallon batches, so it isn't an issue anymore. Last week I did an 11 gallon batch on the outdoor system for the first time, that had a 14.32 (as per beersmith) preboil volume. I had some FermCapS ready but it didn't seem to be a problem.

You can also use a tool like this one to calculate how much water you should start with:
http://www.brew365.com/mash_sparge_water_calculator.php