what's a good boil volume?

[wheatgerm]

I've been shooting for 5.25 gallons in the kettle post-boil on my batches so far. That means around 6.75 gallons pre-boil. My kettle is 7.5 gallons. When I got Brewing Classic Styles, all the recipes are set up for 6 gallons post-boil, which would mean about 8 gallons in the kettle pre-boil for a 90 minute boil. Is there a standard desired post-boil volume for 5 gallon batches? What do others use?

 

[Yooper]

There's no standard. It really depends on your system. A wider pot on a bigger burner will boil off more liquid than a tall pot on a smaller burner. In my old system, I started with 6.25 gallons to end up with 5.25 in the fermenter (1 gallon boil off per hour). But in my new system, I boil off much more. Today I started with 7.25 gallons and finished with 5 gallons! It also depends on the humidity where you live. I would bet the guys in Arizonia boil off far more than the Florida guys do!

If you want to finish with 5.25 gallons, a good place to start is 6.5. If you boil off more than you expected, you can add water to top off. And then add whatever you topped off with into your beginning volume for next time.

 

[Codemunki]

It also depends on the gravity of the boiling wort. Higher gravity wort will boil off more water than lower gravity wort because the temperature will be slightly higher.

 

[Yooper]

It also depends on the gravity of the boiling wort. Higher gravity wort will boil off more water than lower gravity wort because the temperature will be slightly higher.

Really? I've never heard that before. My temp gauge reads about the same whenever I'm boiling.

 

[Codemunki]

Yeah. It works for the same reason that salt makes ice/snow melt. Dissolving anything in water lowers the freezing temperature and raises the boiling temperature. I'm not sure how boil temperature scales with specific gravity, but there is a measurable difference.

This article explains it pretty well.

 

[wheatgerm]

Yeah. It works for the same reason that salt makes ice/snow melt. Dissolving anything in water lowers the freezing temperature and raises the boiling temperature. I'm not sure how boil temperature scales with specific gravity, but there is a measurable difference.

This article explains it pretty well.

I guess 212 is 212 no matter what, but a higher gravity may start boiling at 209 or 210, thus making 212 a more vigorous boil than it would be at a lower gravity. Kind of like if you are on the top of Mt. Everest, the boiling temp is so low that you can actually stick your hand in boiling water and not get hurt. It won't cook noodles though.

 

[Malticulous]

I swear it changes with the weather.

 

[Wellshooter]

I swear it changes with the weather.

Makes sense, atmospheric pressure changes, altitude, humidity are all factors in boil off.

 

[ajf]

I've been shooting for 5.25 gallons in the kettle post-boil on my batches so far. That means around 6.75 gallons pre-boil. My kettle is 7.5 gallons. When I got Brewing Classic Styles, all the recipes are set up for 6 gallons post-boil, which would mean about 8 gallons in the kettle pre-boil for a 90 minute boil. Is there a standard desired post-boil volume for 5 gallon batches? What do others use?

I can guarantee that 8g in a 7.5g kettle is going to make a big mess.
I go for 5.25g in the fermenter, prior to pitching the starter (which brings it up to about 5.5g).

-a.

 

[humann_brewing]

Makes sense, atmospheric pressure changes, altitude, humidity are all factors in boil off.

yep, who would thought that boiling in denver is like at 202 F

 

[Yooper]

I guess 212 is 212 no matter what, but a higher gravity may start boiling at 209 or 210, thus making 212 a more vigorous boil than it would be at a lower gravity. Kind of like if you are on the top of Mt. Everest, the boiling temp is so low that you can actually stick your hand in boiling water and not get hurt. It won't cook noodles though.

Well, yes, I knew that. I just didn't think that a boil of 6.5 gallons of 1.050 wort would be markedly different than 6.5 gallons of 1.065 wort. Well, in fact, I still don't think that it makes a bit of difference actually!

Sure, you may boil at 210.9 instead of 210.4 with a higher gravity wort at my elevation but it definitely won't change the % of boil off measurably. The weather and flame strength do matter- on a humid day you'll boil off less than on a bone dry day- but the OG's effect would be negligble in my opinion. I do notice quite a bit of variation between summer and winter brewing in my location. We have very cold dry winters, and the boil off is greater.

 

[wheatgerm]

Well, yes, I knew that. I just didn't think that a boil of 6.5 gallons of 1.050 wort would be markedly different than 6.5 gallons of 1.065 wort. Well, in fact, I still don't think that it makes a bit of difference actually!

Yeah. Too many variables. I guess there's no substitute for having a measurement stick calibrated to your kettle.

 

[IrregularPulse]

It may in theory boil off more with a larger gravity (don't know if it's true or not), but nothing you'll notice at a home brew scale.

 

[Bizoune]

I usually go with 7.25 gallons down to 6 which leaves me with 5.5 clean wort in the fermenter.

 

[beerman1957]

Here in South-Eastern Arizona I can reach boil at about 203-204 depending on the type of beer. Higher altitude also consumes more fuel due to lack of oxygen, so it all works out in the end.
I use a "Calibrated Dipstick" that I made from a piece of aluminum that I just stick in the kettle and I usually try to end up with close to 5.5 gallons of liquid in the final conical ferment. I will lose some volume when I dump the trub, but I usually end up with just a hair under 5 gallons for the Corny Kegs.