Keggle Evap

[hughyg]

Hi Guys
I calculated my last boil evapouration rate at 30%. Is my boil to vigorous, next time should i just turn it down a little bit? I have made a new keggle and struggled to see the boil through the steam. My sg was spot on, however that was after I added 2L at the 60 min mark of the 90 min boil as i had already reached my target volume.
Chhers
Hugh

 

[razz]

Hi Hugh, 30% is just a waste of gas/power. Perhaps 10-15 % is better to aim for. If the keggle is new then you will take a couple of brews to get your numbers dialled in. I find Beersmith is great for this. And you obviously know how to make up for a short fall in the final volume. Keep at it!

 

[sav]

Mine is set at 12% its pretty close,just a good rolling boil is all ya need.
sav

 

[hughyg]

Hi Hugh, 30% is just a waste of gas/power. Perhaps 10-15 % is better to aim for. If the keggle is new then you will take a couple of brews to get your numbers dialled in. I find Beersmith is great for this. And you obviously know how to make up for a short fall in the final volume. Keep at it!

Thanks
Yep, I was annoyed with 30%. Is it alright to top up the kettle from time to time if need to?
Cheers

 

[schooey]

Not trying to be a smart arse....

I don't know how many times this has popped up, and I'm sure it will again, but like I have said before;

If you are working out your boil off rate in a percentage, you are screwed unless you intend to make exactly the same size batches all the time. Work it out in litres lost per hour, and adjust your brewing software to suit that number. Doing it this way save you bashing your head against a wall later working out what happened with your volumes.

 

[hughyg]

Not trying to be a smart arse....

I don't know how many times this has popped up, and I'm sure it will again, but like I have said before;

If you are working out your boil off rate in a percentage, you are screwed unless you intend to make exactly the same size batches all the time. Work it out in litres lost per hour, and adjust your brewing software to suit that number. Doing it this way save you bashing your head against a wall later working out what happened with your volumes.

So how many L/hr should I use for a 24L batch and a 90min boil? I thought 4 L/hr would be about right??

 

[jayse]

4-5 litres per hour is about right, start at about 31 litres for 90 mins and 24l. You can add more water as you like, I like the three ring burner and standard reg for this as you don't need to adjust it at all.
See how much you lose in the first 30mins and you can tell by the level it is at that you have 60mins left, You can almost do it without a timer when you know what the boil should look like and where the level is at. I don't time the first 30 mins really just wait till its at the right level then start the 60min addition.
The only adjustment I do is place and shroud around the burner if I want a touch more heat if it gets windy outside.

 

[Thirsty Boy]

you need to work it out in % to work out whether your boil is doing the job properly, or whether you are going to hard and wasting gas etc. You want 8-15% of your starting volume... Once you know that's what you have, then its a hell of a lot easier to think in litres per hour.

If you can get it into the 11-12% range for your standard volume, then you can transfer to litre/hour figure and know that even with your volumes up or down a few litres either way... then you are still nicely in the good zone.

 

[Frag_Dog]

I had around 30% boil loss with my 32jet Mongolian with Med. Pressure Reg. I plugged up 18 of the jets with bolts and now I get a nice moderate boil, without using a bottle of gas per boil!!!! My loss now is around 10-15%...

 

[smudge]

I go the opposite way from TB. I like to LOOK at my boil and say "yep, that's what I want" and then work out the %

Regardless of my volume (I do anywhere between 30-90 litre boils) all I want is a moderately rolling boil. Not jumping out
of the boiler, not throwing a few bubbles here and there.......just moving the wort from the bottom to the top "moderately".

I know this topic has had more beatings than a Warnambool Cup winner, but it still plays with my brain that it is such a
perennial topic.

The only way I can explain my theory (and I'm happy to be corrected!) is as follows -

My boiler is cylindrical and can boil 90 litres comfortably. Lets say, when I boil 30 litres with my "moderate" boil I lose 15%
and end up with a one hour boil (forget other losses) into the fermenter of 25.5 litres.

So everyone says "that's 15% boil off, it's where you want to be!"

My "moderate" boil works out in this case at 4.5 litres per hour.

From what I've read, it's the vigour of the boil (not the % boil off) that determines the hot break benefits etc.

So for a given boiler and a given "moderate" boil the the 4.5 litres boiled off per hour will be constant. Sure, I may have to
use more energy with the larger volume to keep my "moderate" boil. But when I do my % boil off in this case it will be
the same 4.5 litres but as a % of 90 litres = 5%.

Long way of saying I agree with Schooey. If you vary your batch sizes use litres per hour and then work out the %.

Cheers,
smudge

 

[Thirsty Boy]

that would be sort of true - if it was only hot break you are talking about. But it isn't. You need to get adequate hot break, drive off volatiles, drop the pH, develop colour, sterilise the wort, isomerise alpha acids and a few other things as well.

The point of what I am saying - is that if your moderate boil is not giving you at least 8% evaporation, then it is not vigorous enough. You are possibly just not evaporating enough liquid to carry away all the volatiles that should be carried away, nor have added enough heat to the system as a whole to complete the other chemical changes. Remember that the vigor you see is only at the surface - but the vigor that counts is spread out through the entire vessel. To put it into a very rough numerical form. You see X amount of wobbles/bubbles which you can see at the surface, which make their way up through Y litres of liquid. so you have a vigor of X/Y wobbles per litre. Double the amount of liquid and you get a vigor of X/2Y or half as much. So your boil "looks" the same but is in fact half as vigorous. Now of course its not anything like that simple, or that linear... i get that. But it does happen a "little bit" like that. You actually want more visible vigor, you are trying to make twice as much stuff happen, through a surface area window whose size has remained the same.

That is the whole point of measuring boil off in % figures. You don't have to guess or rely completely on eyeball & experience. You have a number as well. So you eyeball the boil to make sure its at a rolling boil, but isn't going to go over the top either - then you take a measurement and make sure your evap is in the 8-15% safe zone. The you know its all good.

I am by no means saying you personally should change your process, you obviously have enough experience to tell whether you are having a problem or not. But if people are asking these evaporation questions looking for advice.... then I think the advice that keeps them most surely in good brewing practice territory - is to tell them to keep their kettle at a solid rolling boil that boils off between 8 & 15% of their starting volume.

The % evaporation figure is a measure of boil vigor. That is all it is. You want to work out your volumes, then its a pain in the arse.

TB

 

[hughyg]

that would be sort of true - if it was only hot break you are talking about. But it isn't. You need to get adequate hot break, drive off volatiles, drop the pH, develop colour, sterilise the wort, isomerise alpha acids and a few other things as well.

The point of what I am saying - is that if your moderate boil is not giving you at least 8% evaporation, then it is not vigorous enough. You are possibly just not evaporating enough liquid to carry away all the volatiles that should be carried away, nor have added enough heat to the system as a whole to complete the other chemical changes. Remember that the vigor you see is only at the surface - but the vigor that counts is spread out through the entire vessel. To put it into a very rough numerical form. You see X amount of wobbles/bubbles which you can see at the surface, which make their way up through Y litres of liquid. so you have a vigor of X/Y wobbles per litre. Double the amount of liquid and you get a vigor of X/2Y or half as much. So your boil "looks" the same but is in fact half as vigorous. Now of course its not anything like that simple, or that linear... i get that. But it does happen a "little bit" like that. You actually want more visible vigor, you are trying to make twice as much stuff happen, through a surface area window whose size has remained the same.

That is the whole point of measuring boil off in % figures. You don't have to guess or rely completely on eyeball & experience. You have a number as well. So you eyeball the boil to make sure its at a rolling boil, but isn't going to go over the top either - then you take a measurement and make sure your evap is in the 8-15% safe zone. The you know its all good.

I am by no means saying you personally should change your process, you obviously have enough experience to tell whether you are having a problem or not. But if people are asking these evaporation questions looking for advice.... then I think the advice that keeps them most surely in good brewing practice territory - is to tell them to keep their kettle at a solid rolling boil that boils off between 8 & 15% of their starting volume.

The % evaporation figure is a measure of boil vigor. That is all it is. You want to work out your volumes, then its a pain in the arse.

TB

I dont quiet understand the concept of hot break. Is it the material that sinks to the kettle? Also what sort of pH should I have post boil?