Excessive Kettle Evaporation Loss

[bradsbrew]

Flame suit is well and truely on BUT would you lose less to evaporation using water as opposed to wort?

 

[Thirsty Boy]

I'm just not that sure that "float a takeaway container on the surface" is a great answer.

Well, that's our actual difference then - I am sure its a good answer, its the solution I effectually use to solve exactly the same issue.

As equally I am sure you believe that your proposed solution of turning the heat down so you get less than a rolling boil is an effectual solution. - I don't actually just believe it, I know that what you propose will in fact work to reduce evaporation, I just think that it has other potential issues attached that make it a less than ideal solution.

What you seem to have been doing though, is telling me that I am imagining or misinterpreting an effect that I can both clearly see and in fact measure (I have) ... I will object to this quite strongly and tell you that you're wrong. If on the other hand you were to say something along the lines of "OK, that obviously works, but I think its a bad idea anyway because......" then its a different story. You put your case, I put my case - everyone including the OP can decide for themselves which (if either) of us is right and with any luck at all, someone learns something about brewing on the way.

This is the point is it not?

 

[bum]

I'm just not that sure that "float a takeaway container on the surface" is a great answer.

Dude, you're a cock but you're only a moron when you will it - why are you deliberately misrepresenting his well reasoned position? It only undermines your point when you try to reduce his stance to a small statement when he has gone to great lengths to explain and present many options in regards to the issue. You're making a caricature when everyone else can see real life.

 

[MHB]

Flame suit is well and truely on BUT would you lose less to evaporation using water as opposed to wort?

Actually no - the higher the concentration of dissolved matter the lower the rate of steam loss, given all the other variables stay the same. Quick intro in Wiki

Honestly I can't believe this thread has dragged on to its third page, once you get a liquid to its boiling point it can't get any hotter. Any energy not lots in other directions is available to change liquid to vapour (heat of vaporisation), more heat means more evaporation.

If you want to lower the rate of evaporation turn the heat down.

MHB

 

[PistolPatch]

Morning Mark ,

One thing I don't understand is what are the main problems with having a high evaporation rate apart from needing more water and maybe a bit more gas? I think a lot of new brewers using pots with wide surface areas can get hung up on evaporation rate figures and try and "fix" them by simmering their wort etc instead of boiling it which is a mistake.

As I mentioned above, my evaporation rate for double batches is 9.5% and %19 for singles. The beer tastes the same to me though I am not claiming to have a super advanced palate.

So, are there any differences in the quality of wort produced in large surface area pots i.e. those with high evaporation rates? If not, shouldn't we just concentrate on maintaining the good old rolling boil and put up with needing a bit more water and possibly gas?

Cheers to you,
Pat

 

[MHB]

Morning Pat

The only thing I can say about brewing, with any confidence is that there is rarely a "Right" answer, there are lots of wrong ones, good ones and even better ones.

Wort boiling is a very complex process, we aim to do lots of things all at the same time, the list usually includes - Killing unwanted bugs, reducing the amount protein, ending all enzyme reactions, bittering the beer and removing unwanted volatiles (from both hops and malt) and another half dozen other minor jobs.

To do all of these and to do them properly we need to get a certain amount of energy into the wort that amount of energy will cause about 8-10% of the wort to evaporate.

There are obvious downsides to not putting in enough energy, namely that the above aren't achieved, and problems caused by putting in too much, principally wort darkening and precipitating too much protein (reducing head) stripping of desirable volatiles (good smells) - Oh and your burning $ for no gain.

If you can get the optimum ("Right" ) amount of heat into the kettle (and no more) you will get the best outcome, you know you have the right amount by measuring the evaporation and getting that 8-10% evaporation rate. I know it's hard to tell while the boil is in progress, but that's part of getting to know your system. Simmering isn't the bogey people make out, if you're getting the desired evaporation rate mission accomplished.

Good starting read from the IBD View attachment 02___The_function_of_wort_boiling1_1_.pdf
MHB


PS
Lid's off, the first things to condense are the higher boiling point compounds, putting a lid on encourages these to fall back into the kettle unwanted volatiles need to be carried away by the steam so don't block the escaping vapour.
M

 

[PistolPatch]

Hey, thanks for the above Mark - a good read as usual .

So, for my 45cm diameter pot, my double batches are spot on. When I single batch though even when I have tried simmering, the evaporation rate has still been way above this 8-10% and I did end up with wort clarity problems which I never get with my good rolling boil.

So, the way I am reading all this I should leave my double batches as is and give Thirsty's floatie a try on my single batches. Hopefully I have got this right? (Mind you I am not really worried as the beer tastes fine to me )

From reading the article, one further thing that maybe we could do given the poor shape of home brew kettles, is to perhaps slow the boil down to a simmer for the flavour and aroma additions so as to "preserve the more late hop characteristics"???

Thanks again mate,
Pat

 

[Nick JD]

Any energy not lots in other directions is available to change liquid to vapour (heat of vaporisation), more heat means more evaporation.

If you want to lower the rate of evaporation turn the heat down.

Well said.

 

[Nick JD]

Dude, you're a cock but you're only a moron when you will it - why are you deliberately misrepresenting his well reasoned position? It only undermines your point when you try to reduce his stance to a small statement when he has gone to great lengths to explain and present many options in regards to the issue. You're making a caricature when everyone else can see real life.

Because I know that if one turns their heat down and then covers half the surface the uncovered half will appear to boil twice as strongly - all the vapour is forced to leave the kettle in only half the area. This is not a more vigourous boil, it's a bottleneck in the release of vapour. The same net vigour and evaporation will happen without the floating object at the same temperature ... it's just simple physics.

 

[Thirsty Boy]

Morning Mark ,

One thing I don't understand is what are the main problems with having a high evaporation rate apart from needing more water and maybe a bit more gas? I think a lot of new brewers using pots with wide surface areas can get hung up on evaporation rate figures and try and "fix" them by simmering their wort etc instead of boiling it which is a mistake.

As I mentioned above, my evaporation rate for double batches is 9.5% and %19 for singles. The beer tastes the same to me though I am not claiming to have a super advanced palate.

So, are there any differences in the quality of wort produced in large surface area pots i.e. those with high evaporation rates? If not, shouldn't we just concentrate on maintaining the good old rolling boil and put up with needing a bit more water and possibly gas?

Cheers to you,
Pat

Pat,

Go back a page or two, I explained some of the potential issues with high heat loading on worts. And I repeat, yet again... That high evaporation is not the issue... It is an indicator of an issue. So as mark says, it just tells you whether you are in safe territory, or whether there could be issues.

And yes, if you believe that heat load is a factor in wort/beer quality, then high surface area pots, which require a higher heat load to maintain a given level of boil vigor, can effect the quality of the beer. Of course if you don't think that's true, then it's not particularly important.

I absolutely disagree with Mark on the simmering thing... IMO it is a bugbear, the 8% thing is only part of the picture in a boil, the physical agitation and bubble formation in an active rolling boil, both play important parts in the chemical changes that take place in the kettle... You don't get them in a simmering boil. I might bang on about people reducing the heat load on their kettle, but thats only because people generally aren't aware that too much heat can be an issue, at the end of the day...i'd much rather see any brewer shoving a bit too much heat through their kettle than see them with an insipid boil.

Your 19% boil is only a little outside what most people would consider the "acceptable" parameters, it's high but not insane. You've said previously that you can't tell the difference between your double and single batches, so to you it's obviously not a problem.... Why worry about it?

 

[MHB]

Maybe I phrased it badly enough energy to get ~10% evaporation isn't going to be a simmer, nor is the wort going to be jumping out of the kettle but I think if your evaporation is close to target your getting enough of a boil to achieve all the goals.

Agreed a simmer isn't usually adequate, but I do like Pilsner Urquell, it's reportedly boiled at what could be called a very low boil for 2 hours. So I sort of suspect that Shorter/Harder Longer/Softer boils achieve the same thing.

You know you're getting an adequate boil by measuring your evaporation as a percentage and adjusting you brewing process to hit the targets, just like in crushing grain, mashing or sparging the experience gained in one brew feeds into improving the nest.

MHB

 

[Thirsty Boy]

Because I know that if one turns their heat down and then covers half the surface the uncovered half will appear to boil twice as strongly - all the vapour is forced to leave the kettle in only half the area. This is not a more vigourous boil, it's a bottleneck in the release of vapour. The same net vigour and evaporation will happen without the floating object at the same temperature ... it's just simple physics.

Not simple physics... Your overly simple interpretation of a complex physical system.

But you know best... I must be wrong - after all, I only do it, have measured the results, have formally studied wort boiling and am experienced in observing the phenomenon in question. Stupid of me to think for even an instant that could lead to a valid conclusion.

I'll on deluding myself into thinking that things I can see, measure and understand are real.. Everyone else should listen to you.

 

[Thirsty Boy]

Maybe I phrased it badly enough energy to get ~10% evaporation isn't going to be a simmer, nor is the wort going to be jumping out of the kettle but I think if your evaporation is close to target your getting enough of a boil to achieve all the goals.

Agreed a simmer isn't usually adequate, but I do like Pilsner Urquell, it's reportedly boiled at what could be called a very low boil for 2 hours. So I sort of suspect that Shorter/Harder Longer/Softer boils achieve the same thing.

You know you're getting an adequate boil by measuring your evaporation as a percentage and adjusting you brewing process to hit the targets, just like in crushing grain, mashing or sparging the experience gained in one brew feeds into improving the nest.

MHB

Absolutely. But dependent on an assumption about kettle architecture. In breweries, where kettles are designed for the purpose.... 10% or so evaporation is an indicator that your boil will have been vigorous enough. And that's why we all use the 8-15% range... But home brewers aren't using vessels designed for purpose... They are frequently using vessels that are a serious compromise between volume, cost and flexibility. And that invalidates the assumption about kettle architecture. My brewery for instance is primarily designed for single batches. With my heat source and my normal pre-boil volume, an ideal pot would be about 40L, I would get a great rolling boil and about 12% boil off. BUT - I want to be able to do the odd double batch, so I have a 60L pot instead, and its too big (in diameter). If I put enough energy into it to get a decent boil vigor, I get around 18-20% boil off, and if I try to go with an "acceptable" boil off, I get a truly insipid simmer instead of a boil. So in order for that safe range to apply, I change my kettle architecture. So that's why, in raw terms of driving off volatiles, 8% is enough no matter the shape or size of your kettle.... But it's only an effective indicator of boil vigor in a pot that is close to ideal. Poor old home brewers are left to try and judge what is an adequate boil vigor in the pot they have... And how many threads, including this one, go into that question?

I'm in your camp anyway I reckon.... Most boils I see in other home brewers systems are far more than adequate, mine is a chunk more gentle and I suspect there is many a home brewer who would classify it as too much like a "simmer"

 

[Kieren]

Not simple physics... Your overly simple interpretation of a complex physical system.

But you know best... I must be wrong - after all, I only do it, have measured the results, have formally studied wort boiling and am experienced in observing the phenomenon in question. Stupid of me to think for even an instant that could lead to a valid conclusion.

I'll on deluding myself into thinking that things I can see, measure and understand are real.. Everyone else should listen to you.

:lol:

 

[Nick JD]

I'll on deluding myself into thinking that things I can see, measure and understand are real.. Everyone else should listen to you.

No - I think they should listen to you, Thirsty - but I also think they shouldn't have a lid on their kettle, I think they should just turn down their boil a little.

SMM-->DMS happens at 100C and DMS has a boiling point of 37C. You simply don't need a magama pit to get rid of the unwanted volitiles.

Lidding pots because you say it's a good idea might encourage other brewers to do it, when they don't need to. It's bad practice. I can get the required evaporation from my kettle with the lid almost completely on and the heat turned waaay down. There's a shitload of refluxed DMS getting back into the wort though. I stopped doing this because it was bad practice.

 

[bum]

[Doing 'X'] because you say it's a good idea might encourage other brewers to do it, when they don't need to. It's bad practice.

Is anyone else lolling/raging pretty hard right now?

The irony is delicious/infuriating.

But in terms of your specific frame of reference, TB has specified it is best practice to set it up so that the condensation does not drip back into the wort. Assuming a brewer achieves this where is the harm? Serious question, btw, not stirring the pot. I'm asking because what TB has said seems reasonable and in practical terms the only thing you've present against the idea is "I think you are wrong".

 

[Thirsty Boy]

No - I think they should listen to you, Thirsty - but I also think they shouldn't have a lid on their kettle, I think they should just turn down their boil a little.

SMM-->DMS happens at 100C and DMS has a boiling point of 37C. You simply don't need a magama pit to get rid of the unwanted volitiles.

Lidding pots because you say it's a good idea might encourage other brewers to do it, when they don't need to. It's bad practice.

Have you actually read any of my previous posts in this thread? Seriously... I have repeatedly suggested that what you really want to do is turn your heat down... That the whole point of trying to reduce evaporation is not to reduce evaporation, but to reduce the heat load on your wort... By turning the heat down. that in general... Your heat should always be as low as it can be whilst actually doing the things that need to be done in a boil

But, boils are about more than driving off dms, first there are a host of other unwanted volatiles in a wort, and second volatiles are far from the whole picture. Turning the heat down to a simmer, also effects the way the other parts of the boil happen... It has bugger all to do with DMS. DMS you can fix with a simmer and the appropriate amount of time.

Once again, you interpret over simply, something which is complex.

You put a lid on a simmering boil, and it's bad practice from two perspectives.... If you were to put a lid partially on an over evaporative boil in a kettle that has too much surface area in the first place - so that you are able to turn the heat down and maintain both your active boil and a sufficient boil off rate?? that might be a slightly different thing perhaps?

Anyway, everything reasonable that needs to be said has already been said. More than enough for people who actually read all the words to come to a sensible conclusion. I'm out of this thread. All yours if you want unopposed right of reply mate.

 

[yardy]

http://www.homebrewdownunder.com/index.php?topic=609.0

some info here on this as well

Dave

 

[Peter Wadey]

Sorry,
I could not be bothered reading page after page of this stuff, but as far as not putting your lid on because of the condensate dripping back in,
surely that's a minor hurdle to conserving a little energy (lid partially on, so heat can be turned down a little) ?
I made a little clip years ago that I use to prop the lid up a little bit on the down side so that the condensate drips outside the kettle.
Somebody might find the pics useful.




This last one just to show the whole picture....the lid is usually off a bit more than this during the boil.


Rgds,
Wad

 

[Nick JD]

Sorry,
I could not be bothered reading page after page of this stuff, but as far as not putting your lid on because of the condensate dripping back in,
surely that's a minor hurdle to conserving a little energy (lid partially on, so heat can be turned down a little) ?
I made a little clip years ago that I use to prop the lid up a little bit on the down side so that the condensate drips outside the kettle.
Somebody might find the pics useful.

Rgds,
Wad

That's a great idea - Thirsty, you could do this instead of refluxing all your DMS.