Boil Off Rate Questions

I live in the desert in Southern California. I brewed a lager this past weekend when the weather was about 100°F and 5% humidity. I boiled for 90 minutes and kept the boil rolling harder that I normally would to help fight DMS. At the end of my boil I had boiled off 4 gallons!! My gravity ended up almost spot on after I topped off back to 5.5G. Anyway, my questions are...

-Am I hurting anything by boiling off at such a high rate?
-Should I continue to boil my wort at a strong rolling boil or should I start turning down the gas and trying to just maintain a simmer?

I'm sure everything will be fine either way, but I'm trying to narrow down my consistency so I can produce a more reliable and delicious brew. I want to enter into a brew contest eventually and as everyone knows, the devil is in the details. Thanks!

Yikes! 4+ gallons of boil off on a 5 gallon batch?!?

Two questions: exactly when did you realize this? And what kind of pot are you using for a BK?

Your hop utilization would surely plummet along with the sight gauge reading, and you probably drove the degree of caramelization way up. Otherwise, if you somehow managed not to scorch the wort on the bottom of the pot, it'll probably be beer you can enjoy.

A strong boil is A Good Thing when using a lot of pilsen malt, you want a good bubbling boil to carry out the DMS. But I think you could turn the gas down a little bit and help save the polar ice caps

Cheers!

Yeah...... I was at the 15 min remaining mark when I stuck my I.C. in when I noticed. I turned down the heat to about a simmer, but it was way too late. It is so difficult to gauge how much evaporation I'm going to get around here. On top of that, after 3 years of brewing I still can't decide what is a good roiling boil. I can never decide whether decide whether is too strong or too weak! I'll get it figure out one of these days...

this is my biggest issue with brewing too. i think i have it pretty well nailed down now, my last 3 brews were within a 1/2 quart. i boil off about 2.25 in 90, hard to believe the humidity would have that much of an effect, but i guess so.

I've considered taking a look at this problem. Boil off per hour as a function of volume, surface area, gravity, humidity, and altitude shouldn't be that difficult to solve. At some point, maybe I'll have the time to actually do this.

It is pretty amazing. I have a 15 gallon Bayou Classic BTW. I just "calibrated" my kettle so I am darn near positive that my volumes are correct. I just can't believe I boiled off so much still. That is a crazy amount!

gmcastil said:

I've considered taking a look at this problem. Boil off per hour as a function of volume, surface area, gravity, humidity, and altitude shouldn't be that difficult to solve. At some point, maybe I'll have the time to actually do this.

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Speaking of altitude... I live at about 2300ft above sea level. Maybe that is having an effect too!?

I think your primary factors are kettle geometry, temp, humidity. A nice wide kettle will have higher boil off than a tall skinny one, leaving all other factors the same...it's the exposed surface area.

Was this an all grain batch using Pilsner malt? There is no DMS threat with extract, Pilsner malt is the primary culprit.

I have a pretty wide kettle. I've just never had such a high rate of loss.

This was an all grain batch. All that Pilsner was the whole reason a kept my boil going so strong.

I top off my 20 BK at Hot Break, 30 Minutes, 60 minutes and 75 minutes with boiling water additions. My current BK is Blickman but it leaks out of the weldless fitting a little as well as boil off. I skip additions if I think it wise, but do not let too much boil off happen as I did once and the beer was not what I was hoping for. I am getting a new 45 gal Stout Conical brew kettle this week so we will have a new process as kettles require different a different timing. I got a very much larger kettle so I am hoping to add the water at the start and not have to monitor the volume as much and there will be no leaks from a welded fitting.

That's not a bad idea. Ill try to remember to keep some extra water on hand so I can too off prior to emptying the BK.

helibrewer said:

I think your primary factors are kettle geometry, temp, humidity. A nice wide kettle will have higher boil off than a tall skinny one, leaving all other factors the same...it's the exposed surface area.

Was this an all grain batch using Pilsner malt? There is no DMS threat with extract, Pilsner malt is the primary culprit.

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I would argue that wort gravity and ambient air pressure both have a significant effect as well.