Boil off relative to volume

[Ged]

Guys..Some of the CChurch boys did a wee brew today - James and Dylan ( thanks for your company and help) and discovered that our boil off was ridiculously high..Out of 21.75 wort we boiled off approx 7 litres during the process. Started from cold ( took about 30 minutes to get to boiling) ( and then a further 60 minutes on a rolling boil) - a total of approx 90 minutes from sticking the lautered wort onto the burner to flame out.

Temps seemed stable at around 97.5 to 98.5c according to my thermometer and the wort was definitely boiling away...This kind of screwed up a few calcs but the question that's bugging me is why was it so high - around 30 odd percent boil off...I tried it again with water and from cold to flame out - approx 95 mins again i lost approx 8 litres to boil off on a starter of 21.75...

It it only down to the amount of gas I'm sticking through the burner i.e would we still maintain a boil with a lot less gas? I'm using a 3 burner campmaster ring and they are all on full for the entire period.

Thanks for any opinions...Suffice to say we had to do a fair bit of 'topping up' but everything else looks like it worked.

Thanks

Ged (and the boys)

[Mike Neilson]

When I get to the boil stage I know I allways boil of 8 litres during the boil and adjust the mash water accordingly. But if I get to 1.010 during lautering I just add the remaining water in the HLT to my wort and proceed to boil. I allways have 31 litres at the start off boil to get me to 23 litres.

[Danimal]

You should consider turning your heat down once you get a boil going. The goal is to apply just enough heat to observe a rolling boil: you dont need it "jumping out the pot", it only needs to be moving around the pot with small bubbles rapidly rising to the surface. I have attached a photo of a 12% evaporation boil. It is said that you should be shooting for 10-15% evaporation per hour. When I brew, normally - I start with 27L and boil down to 23, then I lose about 2L with hops and break. Also - dont worry about the temp on your thermometer while boiling: when it's boiling, it boiling. I've also read somewhere that if you boil too hard, you can redisolve the proteins you are trying to coagulate during the boil back into the wort. So to answer your last question - yes, you can maintain a boil wjile using a lot lss gas! P.S - this is JoKing writing on Danimals Realbeer account! (woops - damn cookies).

[Stu McKinlay]

Agree with Danimal/JoKing... you want a rolling boil, not a Rotorua mudpool boil, but you don't need go over board with it...
I've got a 4 ring burner and, as long as it isn't windy, I only need two rings going once I've reached the boil.

Where is the Brendon - the boil expert - when we need him?

[denimglen]

I've got a four-ring burner too but haven't started using it yet. What sort of pot are you using and how much are you boiling off? Just wondering what to expect, thanks :-)

[Stu McKinlay]

14gal, as seen here. I boil off just over 10% per hour (as I've said here before, I'm not bothered about being off on OG by a point or two, so I'm not that bothered if it is 11% or 12%).

Usually 60min boils but I might go a 90min one today. I don't usually have the gass bottle up there... that was an error due to some poor planning (gas line wouldn't reach under the table and the kettle was to heavy to move by the time I realised).

I leave the lid on until it is boiling and then it's off until the boil finishes. I'd call it a bubbling boil rather than an aggressive rolling boil. If I brew a big malty beer, and only half fill the kettle, then I sometimes give it an extra blast for some caramelisation effect... not sure if it works or not... I've not really had a chance to compare.

[denimglen]

Awesome, thanks. I think I'll have to modify the burners so the bottom of the keggle isn't a mile away from the heat. Nice pot by the way. Here's my little work in progress.

[MrC]

How about a partially covered boil making sure that any condensation on the lid doesn't get into the pot? I think I read that somewhere but never tried it.

My boil only just rolls with the kitchem gas hobs on full. Just enough to suffice.

[Ged]

Cheers lads...I suspect the issue is my 'rolling' boil is a tad more vigorous than what is being discussed above!

Will amend for next time and see what happens. Thanks again for the feedback and if the beer tastes bogging then it was Dylan who was in charge :) He had the most books with him for reference!

[James P]

Given we have the same keggle gear I does concern me a little that you lost 8 litres. I checked my last brew, and a BIAB started with 33 litres of water and after absorption, trub loss, evaporation I was down to 22 litres post boil.

By my calculation I lost approx 4 litres to grain (5.5 kg), 2 litres to trub and 5 to boil.

Oh well I will use your calculations for my next brew and see what BeerSmith tell's me!

[Rusty Chch]

Another question we bandied about was whether the volume lost was a linear thing or whether Ged could expect to lose 8l out of every boil regradless of the starting volume?

[Rusty Chch]

Also, cheers to Ged and his family for having us today.

I'm green with envy after seeing Ged's setup. After having witnessed his mashtun in operation, I think I'll be flogging my Visa soon enough

[Kempicus]

Hey Ged how about some photo's of your set up?