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Boil Evaporation

Mashing
#1

if posted elsewhere, I apologize

This past weekend I brewed my standard IPA (All Grain) I collected about 7 gallons of wort with an OG of 1.055. My boil kettle is 8 gallons (I know I need to up that bad bear, but I digress) and I brought my wort to a boil, added my boil hops and had very little, as in less than a cup, boil over. However, after my cold break (roughly 70 degrees f) I only had about 4.5 gallons of wort to ferment.

The outside temp was roughly 72 degrees and the boil was a standard 60 minutes.

Is there a way around this? Typically I do not have that amount evaporate. Would a larger boil kettle, say 15 gallons, with the lid partially on reduce this level of evaporation?

Typically, I like to ferment 6 gallons, so when all is said and done (primary/secondary) I can collect 5 gallons for my keg. By this rate, I will probably have 3-3.5 to keg. Normally, I wouldn’t care if this were a porter or a stout (the not so popular among my MBC friends), but the IPA tends to go fast.

Thanks for the input NB Community.

PROST!!!

#2

You can try to reduce the vigor of your boil a bit, might help a touch. Yes it’d help to start with a larger volume of wort so that your end volume comes out to the desired amount so a bigger boil kettle would help. Boil off isn’t a big deal as long as you account for it though. With the size pot you have I’d just check your volume at 15 minutes remaining in the boil and if you’re on a trajectory to come up short add more water at that point.

Also big wide pots tend to have more boil off that a taller pot of the same volume (surface area of wort exposed to air is a factor in boil off rate).

#3

Thank you Flip. That makes a lot of sense. I am in the process of looking for a larger kettle, so I will look for the taller ones if available.

For now, I’ll cut the flame back as you have mentioned.

Thanks for the help.

:cheers:

#4

A bigger kettle will generally boil off more. Advantage is that you can start with more wort in the pot.

I boil off just over 2 gallons in 60 minutes with a very moderate boil. I start with 7.5 gallons to end up with 5.3 in the fermentor.

#5

Also, don’t forget that the wort shrinks as it cools.

#6

If your money tree isn’t blooming at the moment and a larger kettle is not an option, another thought might be to plan for a slightly higher OG knowing that you would top up your volume with another half gallon or so at the end of the boil.

#7

I just ordered a 10 gallon Tall Boy to compensate for a higher wort volume.

Thank you all for your input.

:cheers:

#8

Having a kettle with headroom is quite nice, you’ll like having the 10 gallon kettle for 5 gallon batches. I use a 20 gallon for my 10 gallon batches which works great, never have a boil over. :cheers:

You may want to eventually look at doing a ball valve on that kettle, way easier than picking up all that work and pouring.

#9

I am sure there is a thread here that gives instruction on how to do it, but from your experience is it rather easy?

I definitely would like to add a 1/2" ball valve to save my back some unnecessary stress :slight_smile:

#10

Little scary drilling through your perfectly good kettle but it is a actually quite easy. Problem is finding a decent step bit that doesn’t cost a ton or a metal hole punch. I used one like this successfully on the couple pots I put valves on. http://www.amazon.com/Neiko-Titanium-St … B000FZ2UOY Here is the an option for a no weld valve. http://www.northernbrewer.com/shop/s-s- … e-kit.html

#11

If you started with 7 gallons at 1.055 and boiled down to 4.5 gallons, then topped up to 5.5 gallons you would get an OG of 1.077. At 4.5 gallons you at 1.086. Did you measure your OG?
This just happened to me where I had to top off with a gallon of water and I hit the OG as expected.

#12

[quote=“mvsawyer”]If you started with 7 gallons at 1.055 and boiled down to 4.5 gallons, then topped up to 5.5 gallons you would get an OG of 1.077. At 4.5 gallons you at 1.086. Did you measure your OG?
This just happened to me where I had to top off with a gallon of water and I hit the OG as expected.[/quote]

Prior to my boil, I had an OG of 1.056 (converted for temp being that my hydrometer is calibrated for 68 deg F). I did not take a reading after my boil though.

Recently, I switched to a Blichmann floor burner; which has about 40k more BTU than my last burner. In addition, I was attempting to do this in an 8 gallon kettle. I did lose a little wort, but not too much or a gallons worth.

I was always under the impression that I would loose 5 points off my SG per each 1/2 gal of H2O. Is this off?

#13

[quote=“andymag”]
I was always under the impression that I would loose 5 points off my SG per each 1/2 gal of H2O. Is this off?[/quote]

Wouldn’t this be percentage based, rather than a fixed number? You certainly would not lose 5 points irregardless of the OG - pre boil.

#14

[quote=“560sdl”][quote=“andymag”]
I was always under the impression that I would loose 5 points off my SG per each 1/2 gal of H2O. Is this off?[/quote]

Wouldn’t this be percentage based, rather than a fixed number? You certainly would not lose 5 points irregardless of the OG - pre boil.[/quote] :lol:

That’s definitely off. Think of it in terms of sugar points. Given a specific volume and a specific gravity you can determine your sugar points. These points never change and you can put them into any volume and predict the SG. You had 1.056 with 7 gallons so you take 56 * 7 to get sugar points of 392. Now irregardless of volume you will always be able to determine gravity by dividing by the volume. In 4.5 gal you get 87 or 1.087, in 5.5 gal you get 71 or 1.071. Even if you boiled down to 1 gallon added back up to 10 gallons and boiled again down to 5 gallons, you would still always have 392 sugar points in the batch.

Clear as mud?

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