Correcting excessive boiloff in new kettle

[joshmk]

I recently switched to a 15 gallon stainless steel kettle for 5 gallon batches, and one unanticipated consequence is a greatly increased boiloff volume. For a 60-minute boil, I have had to collect 7.5-8 gallons of wort in order to finish with 5.5 gallons going into the fermentor.

I have also noticed an acrid flavor that lingers on the back of the tongue in these same batches. Could this be from the concentration of salts, or possibly from scorched wort from too vigorous a boil?

 

[ncbrewer]

I can see where a larger kettle could result in higher boil-off because of more surface area. But the acrid flavor makes me wonder if you've also increased the boil intensity without realizing it.

 

[joshmk]

That may indeed be the case. It seems my idea of a rolling boil is actually considered a violent boil. Will trim way back on the gas next batch and see if that helps. Thanks!

 

[mabrungard]

The boil should be just vigorous enough that you can see that hop and break particles can be seen moving somewhat well. There is no need to have a geyser. The other thing you can do is partially cover your kettle to reduce the loss of steam to the atmosphere. You can't burn wort in the boil. The wort is at 212F or less, no matter the boil vigor. Another thing you can do is reserve a bit of water and add it back to the post-boil wort to bring the volume back to where you expected it to be. If you add that water back in, the gravity should also end up closer to your intended gravity instead of being too high.

 

[bucketnative]

You can't burn wort in the boil. The wort is at 212F or less, no matter the boil vigor.

You most certainly can burn wort in the boil. The surface of the pot at the interface can be much hotter than 212 F, and can scorch the sugars in the wort on the bottom.

 

[DurtyChemist]

You most certainly can burn wort in the boil. The surface of the pot at the interface can be much hotter than 212 F, and can scorch the sugars in the wort on the bottom.

All the sugars are dissolved at a boil unless you're adding extract at the start of the boil.

2 gallons of boil off would be a strong boil to say the least. I use a keg to boil and as long as I'm seeing the bubbles coming up and looking like a low boil I leave it. I can see hot break moving around and the wort being mixed up by the rising bubbles. I wish I bookmarked the page I had showing different videos of boils and what to call them.

Edit: I do even less of a boil than this.
http://youtu.be/T1C8cZkc0Oo

 

[fun4stuff]

I have a 19 gallon pot that has a 2 gal/hr boil off rate with a roaring boil. I was able to get it down to 1.1 gal/hr by turning the gas down and covering 90% with the lid.

 

[fun4stuff]

You most certainly can burn wort in the boil. The surface of the pot at the interface can be much hotter than 212 F, and can scorch the sugars in the wort on the bottom.

Only time I've heard of people managing to burn wort is when they added malt extract to a boiling pot without taking it off the burner or stirring.

 

[joshmk]

Awesome info, thanks everyone. Will reduce the boil vigor and partially cover next time.

 

[JosephN]

Just something to note that goes against what some have said above. Also I'm not trying to claim I know it all or that my info is solid. But, Dr Chales Banthope of UC Davis, said that you NEVER want to cover your pot during the boil unless you have a fan to suck the boil off, vapors, away. He said this leave the precursor of DMS, as well as a lot of the other things you want to boil out. I believe this guy to know what he's talking about since he is highly noted in the brewing community. Also you can go listen to a recent "brewing network, or "beer smith" podcast and he talks about that. He goes more into it on the beer smith one.

Either way, cut the gas back and do not cover it, and you'll be good.

 

[fun4stuff]

Just something to note that goes against what some have said above. Also I'm not trying to claim I know it all or that my info is solid. But, Dr Chales Banthope of UC Davis, said that you NEVER want to cover your pot during the boil unless you have a fan to suck the boil off, vapors, away. He said this leave the precursor of DMS, as well as a lot of the other things you want to boil out. I believe this guy to know what he's talking about since he is highly noted in the brewing community. Also you can go listen to a recent "brewing network, or "beer smith" podcast and he talks about that. He goes more into it on the beer smith one.

Either way, cut the gas back and do not cover it, and you'll be good.

DMS from not fully uncovering pot during the boil is another one of those homebrew myths. While I'm not saying it never occurs, the etiology is probably more complicated and multifactorial. If you do a search of these forums you'll see a ton of people partially cover and do not have issues. Pro brewing systems limit evaporation to 5-8% per hour. If your concern you can always do a vigorous boil for the last 5-10 mins uncovered.

 

[mabrungard]

said that you NEVER want to cover your pot during the boil unless you have a fan to suck the boil off, vapors, away.

All large-scale professional kettles are covered and don't typically employ a fan to exhaust them. Leaving the surface of the wort totally exposed to the atmosphere can result in excessive exchange with the atmosphere (read: you lose too much water by evaporation). Pro's typically boil off about 5 to 8 percent of the initial wort volume during their boils. Its darn hard to keep it that low in our homebrew systems without covering the kettle a bit.

 

[augiedoggy]

Something thats not really been brought up that I can tell is the dimensions of the kettle?

a wide kettle will always have a larger amount of open surface area and larger amount of Boiloff as well as require more emergy to boil evenly... A taller narrow kettle has the advantage of being more efficient as well as being more useful for both smaller batches as well as larger batches in an electric setup (doesnt apply here).

 

[JosephN]

Like I said, I am no scientist in a lab that can test for such things, but Charles has worked with labs to test things. I trust him to know what he's talking about and I choose to go with what people that have much more experience than me and have actually used labs to test for such results. Also he gets into talking about elevation and the actual temp needed to get wort to boil. He said that you really should account for excess boil time at different elevations, and much more.

Anyways, I'm an electrician and have been a part of wiring up at least 4-5 breweries here in Nashville. While the kettle is covered, and you see the evaporation pipe and no motor/vent fan, they are usually on the roof. So just because you don't see it doesn't means they don't have one. While some commercial breweries don't have them, they have been known, depending on the time of year (why that matters I don't know), if they don't have a vent fan then there is usually a build up of DMS in the condensation and it drips back into the wort.

Anyways you all do what you thinks right, or what works best for your taste buds. Personally I don't think that there is any one right or wrong way to brew beer. If it's is good to you then rock on.

 

[joshmk]

Something thats not really been brought up that I can tell is the dimensions of the kettle?

a wide kettle will always have a larger amount of open surface area and larger amount of Boiloff as well as require more emergy to boil evenly... A taller narrow kettle has the advantage of being more efficient as well as being more useful for both smaller batches as well as larger batches in an electric setup (doesnt apply here).

I went from boiling in an 8 gallon kettle to boiling the same batch size in a 15 gallon kettle. It would have to be an absolute chimney of a 15 gallon pot to not increase the exposed surface area . I think one reason the boils have been so violent in this pot is certainly the increased diameter-height ratio, but also because this new pot is tri-clad and has better heat transfer than the old one. Ergo, the same amount of gas as I previously used on the old kettle translates into more heat applied to the wort in the new kettle. Pretty nice problem to have.

 

[poptarts]

I always boil off about 1.5 gallons per hour doing 5 gallon bathes. Never had a taste issue that I have noticed. Why is bigger boil off an issue?

 

[joshmk]

Not necessarily the volume of boiloff per se, but the violence of the boil that caused the excessive vaporization is what I believe may be the issue.

 

[Singletrack]

One solution is to brew larger batches. Not sure what this solves, really, but it gives you more beer!

 

[joshmk]

One solution is to brew larger batches. Not sure what this solves, really, but it gives you more beer!

Getting there

 

[augiedoggy]

I went from boiling in an 8 gallon kettle to boiling the same batch size in a 15 gallon kettle. It would have to be an absolute chimney of a 15 gallon pot to not increase the exposed surface area . I think one reason the boils have been so violent in this pot is certainly the increased diameter-height ratio, but also because this new pot is tri-clad and has better heat transfer than the old one. Ergo, the same amount of gas as I previously used on the old kettle translates into more heat applied to the wort in the new kettle. Pretty nice problem to have.

well I use a 15gallon kettle as well and I get 1 gallon per hour boil off ... So to be getting 2+ your kettle has to be wider than tall or you have to be boiling at a pretty ridiculous rate from the way I see it.. I would focus on regulating the boil I Guess.

My point was if you are using something like a concord pot vs a megapot your going to get more boiloff from the concord even thought they are both 15 gallons.

 

[joshmk]

I am using a 15 gallon Spike Brewing kettle. It is not wider than it is tall, but because the diameter of the pot itself is larger than my previous kettle, there is simply more surface area exposed regardless off the diameter/height ratio.

 

[joshmk]

Well folks, today was a quiet day. Which is somewhat of a revelation, since my brew days typically involve a rather loud propane burner! I cranked my gas waaaay back and put the lid most of the way on, and still have a good amount of movement in the kettle. It is amazing how much quieter this thing is running now. Clearly my previous boils in the new kettle were quite violent comparatively. At 58 minutes into a 90-minute boil, I have lost almost exactly 1 gallon. I would typically have lost 2 gallons at this point. I greatly appreciate your help!