Rate of Boil? What's best?

I know this isn't specific to all grain, but that's the type of brewing I'm doing so I'm putting it in this forum. Feel free to move if appropriate.

So I'm having a heck of a time with boil-off. After having some issues on previous brews, I ran a test yesterday. Boiled 9 gallons of water for 30 minutes. My final volume after cooling - 7 gallons!!!!!

I thought I was boiling at a "rolling boil" but I'm thinking it was way to vigorous or something because that seems like a crazy boil-off rate.

The problems all started when I switched from a keggle to a 15gal megapot. The megapots are 19" in diameter so there's a significant increase in surface area there.

I looked up online and the best description for levels of boil I could find was from wikipedia and was as follows:

Levels of boiling
In Chinese cuisine, particularly tea brewing, one distinguishes five stages of boiling: shrimp eyes, the first tiny bubbles that start to appear on the surface of the kettle water, crab eyes, the secondary, larger bubbles, then fish eyes, followed by rope of pearls, and finally raging torrent [rolling boil].

In detail:
- shrimp eyes
about 70-80 °C (155–175 °F) – separate bubbles, rising to top

- crab eyes
about 80 °C (175 °F) – streams of bubbles

- fish eyes
about 80-90 °C (175–195 °F) – larger bubbles

- rope of pearls
about 90-95 °C (195–205 °F) – steady streams of large bubbles

- raging torrent
rolling boil, swirling and roiling

Click to expand...

so what's the right level of boil? i had two weak of a boil (i think) a couple brews back and ended up with crazy chill haze, so i'm trying to find the sweet spot on these kettles so i don't lose 4 gallons an hour!!!

thanks folks for the help.

the problem with those definitions is... a rolling boil can be just that.. a rolling boil or a vigorous rolling boil or a VERY vigorous rolling boil. they'll all be 212 (unless adjusted for altitude) but they'll boil off a different amount. You also have to look at the atmospheric conditions. cooler air and dryer air will allow a faster boil off due to evaporation. A pot with a larger surface area also contributes to greater boil off. For MY kettle I adjust the flame to just maintain a steady rolling boil. With that I boil off approximately 1.5 gallons per hour. If I increase the flame to have a very violent rolling boil, I can easily boil off 2-2.5 gallons per hour. The key is, to learn how much you do boil off and adjust the boil volume for your equipment. if it means boiling off 3-4 gallons per hour, then you'll know what to expect

Good question. Picture's worth a thousand words so here's mine. 0.75/gal hr and I'd consider it a vigorous boil:

What Jkarp posted is indeed a very vigorous boil. All you really need is a rolling boil, which means the surface of the liquid is moving. Not just little bubbles popping up, which is a simmer,but actual turnover of the wort.

okay... i'll run another test and see what i can come up with. i went with 15 gallon pots in the hopes of doing 10 gallon batches... if i can't get my boil off under control, i'll have to stick to 5 gallons max!!! LOL

thanks for the info.

This particular subject drives me nuts. There is no right answer. I can easily have a one gal. difference in boil off depending on the weather and on how high the flame happens to look to me on any given day. The best I have been able to do is to monitor the wort leve in the boil and make small adjustments depending how it looks throughout.

ya... i guess my main concern isn't controlling the boil off itself - i can and have done that. the thing that worries me is that in doing so, i didn't have a vigorous enough boil on one of my brews a few weeks back and ended up with an IPA that looked like a Hefe!!

so now i'm paranoid about going to easy on the boil and not precipitating the proteins out of the wort.

i guess it'll just be trial and error. wish there was a way to quantify the boil rate though!!

One guys super vigorous 60 minute boil probably accomplishes the same as another 90 minute slow boil. Trial and error is correct imo and you develop your methods over time. My last brew indoors was one of the more vigorous boils I've done and the damn floor was soaking wet from all the condensation in the room. Need a better exhaust or go back to a slower boil.