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Old 04-10-2014, 05:41 PM   #1
smyrnaquince
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Default Boil-Off Too High

I do stovetop batches with a target of 2.5 gallons of beer into bottles. Walking back up the chain, I get:

2.50 into bottles
2.75 into fermenter
3.00 end of boil (at ambient)
3.12 end of boil (at boiling temperature)

My usual boil-off is 0.9-1.0 gal/hr, putting my pre-boil volume (at boiling temp) at 4.02-4.12 gallons. I realize that this is a reasonable range of wort boiled off for 5-gallon batches, but recall that I am doing half batches.

Doing the math, my boil-off rate is
0.9/4.02 = 22.4%
1.0/4.12 = 24.3%

This is a lot of boil-off as a percentage (typical being more like 10%), which means I am throwing a lot of heat into the wort. I've tried turning down the setting on my stovetop burner, but can't get it to a lower boil without killing the boil. I suspect that this has to do with the on/off nature of an electric coil burner and the pot diameter.

My concerns with this high boil-off are:

  • Bad effects on the wort taste. I've read about excess melanoidin production with excessive boils; maybe other bad things happen, as well. (I should mention that I've been trying to figure out an off taste that shows up in my lighter-colored beers.)
  • A waste of electricity
  • A lost opportunity to make larger batches with the same set-up. If I could get the boil-off to 0.5 gal/hr, I could make a batch that was 0.5 gallons larger

Here is what I've thought of to get the boil-off rate down:
  1. Reduce the heat. (Tried this, doesn't work.)
  2. Use the lid to cover half the pot. The partial cover should restrict how much wort volume I lose to steam, but still let enough out to address DMS concerns. I would still be throwing a lot of heat into the wort, though.
  3. Use the lid to cover half the pot and reduce the burner setting. The partial cover should help me maintain the boil at a lower burner setting, so I'd throw less heat into the wort.
  4. Boil for 30 minutes instead of 60. Just as much DMS should boil off (as a percentage of my wort size) as would a normal-size batch boiling for 60 minutes. Total heat into the wort would be half of what I have now. I'd have to adjust my bittering hops due to the shorter boil.

I'm leaning toward reducing the boil time because that is easier to control than judging how much a half-covered pot would boil off.

Thoughts?
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Old 04-10-2014, 05:56 PM   #2
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The shape ratio of height to width plays a pretty significant role in boil off rate. Tall and skinny will have a smaller surface area than short and wide, allowing for less boil off.

I would agree that an electric coil burner is probably not optimal. You're probably needing to keep the heat on higher to accomplish the same amount of boil. You need it to remain boiling even when the coil kicks off, meaning you likely need to use a higher setting than if the silly thing stayed on consistently.

I would avoid using the lid. The DMS is obviously a concern, I believe if it hits the lid, it will re-condense and drop back in. This is obviously counter productive.

As for the boil time, that's an interesting one. I regularly do a 60 min boil on even my 1 gallon batches, but haven't really put any thought into why. I know with extract you can generally reduce boil time significantly since you're mainly wanting to sanitize the extract and fiddle with your hops, but I don't know what the effects of a shorter boil on an all grain or partial would be. Pilsner malt grain bills generally require a 90 minute boil due to excess DMS, so off the top of my head I would guess the standard 60 min boil is also DMS related.

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Old 04-10-2014, 09:34 PM   #3
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You need a 60 minute boil for hop additions.
I have also struggled with boil off rate so high, that it is outside the recommended range. I boil off 2 gal. per hour, and I'm doing 5.5 gal. batches, so I'm well over 20% (10-20% is the suggested range). There are pod casts that talk about this.
I have also had some weird off flavors... kind of a sickening sweet malty taste, that I've tasted in store bought beers as well.
I must say that I have not tasted it since moving from RIMS to HERMS, and I did find evidence of scorching on my element when using RIMS, so maybe it wasn't the boil-off rate after all.
I think that for smaller batches it's more pronounced, but I'm not ready to move to a 10 gallon system.

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Old 04-10-2014, 09:55 PM   #4
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The DMS is one thing I am wondering about. If, on a normal batch, you could boil off 1 gallon in one hour (at 1 gal/hr) or 1 gallon in 30 minutes (at 2 gal/hr), would you get rid of the same amount of DMS either way?

I just did some Googling and found arguments both ways, but also found people doing 30-minute boils with good results.

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Old 04-10-2014, 09:58 PM   #5
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Quote:
Originally Posted by acidrain View Post
You need a 60 minute boil for hop additions.
I did mention that I'd have to adjust my bittering hops due to the shorter boil. You can get just as many IBUs from a 30-minute boil as a 60-minute boil if you are willing to use more hops. Because of my small batches, I typically don't use the full ounce package of hops, so using more won't cost me anything.
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Old 04-10-2014, 10:11 PM   #6
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Remember that the same amount of liquid will boil off in the same pot if boiled for the same amount of time. So figuring it as percentage of volume is immaterial.

What I mean is this- I have a keg for my boil pot. If I make a ten gallon batch I start with 12 gallons. I boil off just about two gallons per hour in the winter. If I make a Five gallon batch I start with 7 gallons. If I make a 2.5 gallon batch, I start with 4.5 gallons. The actual volume that is boiled off is not important but it has no value at all to consider the percentage boiled off as that can vary greatly based on batch size.

If you live in Arizona you'll boil off more than the folks in Florida. That's fine.

You want a nice rolling boil. For many people, one gallon per hour boiled off does that, especially in a humid climate but it could be more in a dry climate. As long as you're not getting excess Maillard reactions, similar to caramelization, then the boil off amount isn't excessive.


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Old 04-11-2014, 01:50 AM   #7
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Very true Yooper, but...
I only recently learned that boil-off rates in percentages have their purpose. I only cared that if I know my boil-off rate in gallons per hour so I can accurately predict my volumes.
Turns out that off (caramel) flavors can be a by product of the boil-off rate (as ratio or a percent) being too high.
This can easily be cured with bigger batches.
As you said, the boil-off in gal/hr will stay the same, but the ratio will change if you make a bigger batch, and the maillard reaction lessened.

As for solving the short boil with more hops... it doesn't work that way. There will be more aroma and less bittering. It will absolutely affect the taste of the beer.

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Old 04-11-2014, 02:48 AM   #8
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What's your elevation. Where I live is hot and dry and I'm at 5500-feet. I set my boil off at 18%/hr.

Edit: never mind. MA isn't high elevation.

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Old 04-11-2014, 01:28 PM   #9
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Quote:
Originally Posted by acidrain View Post
Very true Yooper, but...
I only recently learned that boil-off rates in percentages have their purpose. I only cared that if I know my boil-off rate in gallons per hour so I can accurately predict my volumes.
Turns out that off (caramel) flavors can be a by product of the boil-off rate (as ratio or a percent) being too high.
This can easily be cured with bigger batches.
As you said, the boil-off in gal/hr will stay the same, but the ratio will change if you make a bigger batch, and the maillard reaction lessened.

As for solving the short boil with more hops... it doesn't work that way. There will be more aroma and less bittering. It will absolutely affect the taste of the beer.
Yes, but my point was that 1 gallon an hour wasn't excessive- no matter the size batch. It's actually probably on the low side. You want a rolling boil, but not so much that there are excess maillard reactions created. That won't happen with less than a rolling boil, and slowing the boil is NOT the way to fix this issue.

Actually, there is no issue that I can see. It doesn't appear that there is a problem at all with the finished beer.
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Old 04-11-2014, 02:05 PM   #10
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I always talk about boil-off in gal/hr. In my original post, I brought up % for use as a proxy for the amount of heat I am pushing through the volume of wort. If my boil-off is twice someone else's, then it seems to me I am pushing a lot more heat through my wort than they are. I explained that in my original post, as well as my concerns with this and proposed ways to reduce my boil-off.

I agree that hop flavors in the final beer will be different with hop additions at 30 instead of 60, but AFAIK, I can increase the amount of hops to get the same IBUs in the finished beer with additions at 30 instead of 60. The flavor issue is a good one, though.

It sounds like I'll just have to try the partial cover with lid to see what happens. I realize that I am talking % again, but if I lose 0.5 gallons out of 4 to boiling and someone else loses 1 gallon out of 8 to boiling, I'd say we both boiled off the same amount of DMS from our batches.

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