# Poll: What's Your Evaporation Rate?



## ozpowell (7/5/08)

Surprisingly, I haven't managed to find a previous poll on this topic. I consider mine to be quite high (around the 20% mark), that's why I'm interested....


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## NickB (7/5/08)

Mines pretty high as well. In 90 mins I boil down from 37L to around 25-26L in the kettle. I voted 20%+. But hey, it works for me! Vigorous boil in a 50L SS 'vessel'.

Cheers


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## AndrewQLD (7/5/08)

I can't reply to your poll because I don't know what my % loss is.

I do however know that I lose 6 lt per hour regardless of the size of my boil volume.

But I don't really think we need to go there :lol: 

Andrew


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## Cortez The Killer (7/5/08)

I've set promash to 3L per hour 

I don't find that a % is consistent with changes in volume

There was a thread on point and I think that it was resolved (or argued anyway) that litres per hour was more pertitent

Cheers


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## Julez (7/5/08)

NickB said:


> Mines pretty high as well. In 90 mins I boil down from 37L to around 25-26L in the kettle. I voted 20%+. But hey, it works for me! Vigorous boil in a 50L SS 'vessel'.
> 
> Cheers



I reckon for the purposes of the poll, the measurement should be standardised!! The % loss is the hourly loss in relation to the vessel size, *not* the qty of wort in it. 

e.g. lose 5L in one hour, kettle is 50L = 10% evap. 

This is a consistent (not diminishing) rate of loss that applies almost irrespective of wort volume. 

In the case of Nickb, your rate of loss would be 8L/hr (12L/90mins), divided by kettle volume of 50L = 16%. 

It took me a while to figure this out a few months back, as I totally bollocksed up my anticipated evap qty in my first AG by misinterpreting this rate calculation  .


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## Julez (7/5/08)

Cortez The Killer said:


> I've set promash to 3L per hour
> 
> I don't find that a % is consistent with changes in volume
> 
> ...



Hey Cortez, the % rate is consistent in relation to the vessel size. So long as you work it out as a % of vessel size, not wort volume, as I explain in my previous post. But yeah different way of saying same thing. 

Cheers :icon_cheers:


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## Guest Lurker (7/5/08)

AndrewQLD said:


> But I don't really think we need to go there :lol:
> 
> Andrew



Anyone feeling dizzy?


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## Prawned (7/5/08)

I think mine is around 8lts/hour.. i like watching it boil like crazy  not so great on the gas bill though


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## peas_and_corn (7/5/08)

A little over 20%- Promash is normally set to 20% but I think I should boost it by a bit, probably only a couple %.


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## Stuster (7/5/08)

AndrewQLD said:


> I can't reply to your poll because I don't know what my % loss is.
> 
> I do however know that I lose 6 lt per hour regardless of the size of my boil volume.
> 
> ...



+1 to all this. Evaporation between 5L and 7L depending on how hard I boil, but usually 6L.


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## the_fuzz (7/5/08)

go from 27L down to 23L in 60mins - I use a lid with small holes in it to help prevent boil overs


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## Tony M (7/5/08)

AndrewQLD said:


> I can't reply to your poll because I don't know what my % loss is.
> 
> I do however know that I lose 6 lt per hour regardless of the size of my boil volume.
> 
> ...


Lets go there. The evap rate can only be measured in litres/hr. When you know this, you add this to your finish volume, so if you evap 6 litres and want 24 to run to the fermenter, you start with 30 litres. If you want 48 litres, you start with 44 litres. If you start thinking in percentages, you'll end up in trouble.


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## Julez (7/5/08)

Tony M said:


> Lets go there. The evap rate can only be measured in litres/hr. When you know this, you add this to your finish volume, so if you evap 6 litres and want 24 to run to the fermenter, you start with 30 litres. If you want 48 litres, you start with 44 litres. If you start thinking in percentages, you'll end up in trouble.



This can be expressed as a percentage of the kettle volume, but there really isn't any point to it. As you say, it's always a consistent number of L/hr. However, your kettle size doesn't change during a boil either, so if you always lose 5L and your kettle is 50L capacity, you always lose 10%/hr, irrespective of batch size. 

People keep making the mistake of calculating the evap in L as a % of the wort volume, rather than their kettle volume, but that is totally unreliable as it will continue to vary with batch size. 

So for the purposes of this thread, if you really want to compare your losses to someone else's, the only way to do it is to compare your % loss, calculated as evap in L, divided by kettle volume - NOT wort volume!!

For the purposes of your own water calcs though, the L/hr figure is far more practical to work with. 

'nuff said


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## newguy (7/5/08)

I lose 8.7l in 90 minutes. All of my boils are at least 90 minutes, sometimes more for styles that require it. This is for double batches - I end up with ~43l in the kettle when I'm done, and usually leave behind about 1l with the trub. That's about 17% for 1.5 hours, or about 11% in 60 min, assuming things are linear, but they're not. Close enough.


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## TasChris (8/5/08)

I lose 7l/hr out of a keg shaped kettle using a NASA burner.
This result is fairly consistent.
The hole in the kettle is fairly large and I don't cover it at all

Chris


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## RobW (8/5/08)

Stuster said:


> +1 to all this. Evaporation between 5L and 7L depending on how hard I boil, but usually 6L.



+2


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## Cracka (8/5/08)

RobW said:


> +2






+3 But don't tell anyone I've only done one AG h34r:


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## Adzmax (8/5/08)

I think mines about 15%. I reckon the evap rate of water might be different to wort though and I also think the volume of water migth play part so I need to do some more reasearch here 

What I need to do is buy some dowel, fill my boiler 1ltr at a time and put markings on it so I can just use the dip stick to measure. I have the wood, just waiting for the next brew day then I can work it out more acuratly.


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## Pumpy (8/5/08)

Interesting Poll I am in the 13% band which appears to be average 

Pumpy


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## Thirsty Boy (8/5/08)

I aim for 15% per hour of my pre-boil volume and will manipulate my system to make sure that I get it.

I'd love to go there again ... but it been done so many times in the last year or two that I think we are all over it


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## mikem108 (9/5/08)

about 6 litres /hour depending on the weather


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## floppinab (9/5/08)

Depends a lot you kettle setup this one. I've got a relatively short/ squat (just trying to remember the diameter, around 80 odd cm I think) kettle that'll fit around 100L. When I first started full boils I didn't realise just how much water I was losing and how short my post boils were. In terms of the poll I'm well over 20%, probably sitting at around 8L/hour.
No doubt your thinner taller kettles will have significantly lower evap. rates.


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## mark_m (9/5/08)

I use a cut down 80L keg on a 3 ring burner with variable reg.
Having little surface area, evaporation is only 6-7%/hour (5-6L over an 80min boil - double batch).
I would describe th boil as "gentle rolling" rather than "vigorous".
Generally use a little koppafloc toward the end & have been producing clean, clear beers.
Mark


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## Steve Lacey (9/5/08)

> I have the wood, just waiting for the next brew day



Happens to me sometimes too. Just the thought of getting out all that gleaming stainless.


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## mckenry (12/4/09)

Would someone mind helping me with beersmith please? It's drivimg me mad.

Here are the statistics for yesterdays brewday.

I collected 45.2L from my mash tun. There was 0.5L liquid in the mash tun at end of day
So pre boil is 45.2L @ 1.045 - 1 hour boil and I'm left with 36.2L @ 1.058 in my 80L kettle. 
So 9L boiloff in 80L = 11.25%
There was 2.6L lost to trub & deadspace.

If you see below, it doesnt make sense to me. Why does it say only 4.74L boiloff?? and that the boil volume is only 41.94L ?? I no chill, so I put the chill loss at 0.

Somebody please point out why or where I am going wrong before I bash someone. Only me & the mrs here right now - and it wont be me... :lol: :lol:


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## mckenry (13/4/09)

mckenry said:


> Would someone mind helping me with beersmith please? It's drivimg me mad.
> 
> Here are the statistics for yesterdays brewday.
> 
> ...



After much freaking around & reading here - I have decided I need to leave my evap @ 20% per hour. This way beersmith spits out the right water for me. It may be that my _real _ boiler efficiency is around 11% when done per kettle size, but beersnith definitely works it out as (pre boil volume - post boil volume) / pre boil volume. 
exerp from beersmith.com - see here - efficiencies

Evaporation Rate - Enter the percent of wort that boils off in an hour with your system. You can start with 9-10% to get you in the ball park. If you do not know your rate, you can run a test next time you brew - just record the volume at the start of boil and record it again after an hour of boiling. The evaporation rate is: 
Evap_rate = 100 * (volume_at_start - volume_at_end)/ (volume_at_end)

So, with all the debate, I will leave it as beersmith intends and it will be all good as long as I keep doing similar sized batches. 
If I go a bit under or a bit over - so what? It'll be good enough for the home environment. :beer:


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## Stuster (13/4/09)

mckenry said:


> So pre boil is 45.2L @ 1.045 - 1 hour boil and I'm left with 36.2L @ 1.058 in my 80L kettle.
> So 9L boiloff in 80L = 11.25%



It seems like you've worked it out, but really the 80L is the volume of the kettle , not the volume of liquid you have in it which is what you are evaporating from.  So 9L out of 45L is 20%. Set that as your evaporation rate. Also, you can set your final volume there to 36L.

In fact, the evaporation won't really change even if you do a bigger/smaller batch as it's dependent on the surface area rather than the volume underneath it, but as you say it'll do for the homebrew level. Once you know your system you know yourself how much you will boil off and can calculate water additions based on that rather than on what Beersmith says.


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## mckenry (13/4/09)

Stuster said:


> It seems like you've worked it out, but really the 80L is the volume of the kettle , not the volume of liquid you have in it which is what you are evaporating from.  So 9L out of 45L is 20%. Set that as your evaporation rate. Also, you can set your final volume there to 36L.
> 
> In fact, the evaporation won't really change even if you do a bigger/smaller batch as it's dependent on the surface area rather than the volume underneath it, but as you say it'll do for the homebrew level. Once you know your system you know yourself how much you will boil off and can calculate water additions based on that rather than on what Beersmith says.



Yeah, I only posted this up as most experienced guys say that evap rate can only properly be expressed as a L/hour figure, not a %. Most will boil off (for e.g.) 9L/hour regardless of whether the start volume is 40L or 60L. Therefore the evap rate will be different depending on different start volumes (doing it the way beersmith likes it). BUT, if you always boil off 9L reagrdless of batch size, the 9L/hour per boiler size remains constant. Hope I've explained this well enough :huh:


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## buttersd70 (13/4/09)

Mckenry
even though you No Chill, you would still have loss to chilling...it's just that it takes overnight instead of 20min  The chill loss is due to the liquid contracting as it cools....

Just to complicate things further.....

As far as the loss to trub setting, there has been a bit of discussion about that setting for a long time....if you enter the loss there, beersmith has a glitch that throws the hopping out. It doesn't recognise that the 2.6L (or whatever amount) left in the kettle is _hopped_. (ie it somehow imagines that all of the isomorised alphas make it _out _of the kettle, instead of being distributed between what goes _out _of the kettle, and what stays _in _the kettle, if you know what I mean...)...so, many people get around this by setting this loss to 0, and increasing the batch size by the relevant amount.


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## flattop (13/4/09)

Around 2L an hour in a narrow urn which is under 10% but i haven't yet achieved the kind of boil i want.


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## mckenry (13/4/09)

buttersd70 said:


> Mckenry
> even though you No Chill, you would still have loss to chilling...it's just that it takes overnight instead of 20min  The chill loss is due to the liquid contracting as it cools....
> 
> Just to complicate things further.....
> ...



ahh butters... geez man, I thought I had it nailed... Yeah, thought about the chill loss, but decided it wasnt a big enough loss to bother with.
As for the trub loss - thanks for the info and will adjust accordingly.
Out of interest, how much IBU are we talking when beersmith ignores the trub volume when calculating IBU? If I have designed a recipe at 25IBU then in reality I'll get ???? My guess is this - 2.6L out of 36L is roughly 7.5% so is beersmith underestimating by 7.5% ? or giving me +7.5% in those 36L collected?
cheers butters
mckenry


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## buttersd70 (13/4/09)

the difference it makes is that if you have 2.5L trub loss, and 25L to the fermenter (for easier amounts, for the sake of discussion), the IBU needs to be calculated with 27.5L in mind (25L hopped wort to fermenter, 2.5L hopped wort, trub and crap left behind)....but beersmith doesn't, it ignores the trub amount, and works it out as 25L volume only, so it would be.......under. Underestimating the IBU is the magic direction. (had a few, and needed to vocalise it to remember which way it was. :lol: )


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## mckenry (13/4/09)

buttersd70 said:


> had a few, and needed to vocalise it to remember which way it was. :lol:



yeah me too :lol: thought it would be under estimating. So I need to go for a 38.6L batch when I want to collect 36L, leave losses to trub at 0 and I will get the right IBU for the collected amount.

Is this a problem when converting other peoples recipes? As I said, had a few :lol: and its getting hard to think this out


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## mckenry (13/4/09)

By the way, does Promash have these problems?


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## Screwtop (13/4/09)

Evaporation percentage rates don't work. Boiloff rate for my system is usually 6L per hour.

Screwy


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## buttersd70 (13/4/09)

mckenry said:


> By the way, does Promash have these problems?



I don't believe so....

Conversion of other peoples recipes is always a bit of an issue; certain assumptions need to be made. Although, even if the same brewing software is used (and to take it one step further, even if the same equipment is used) there will be a certain amount of difference from one brewers technique to another. I know that, for example, DrSmurtos Golden Ale varies from brewer to brewer, even if they remain faithfull to the recipe and don't tweak it. I've had a few of these, brewed by several different people, and all are subtley different. The main point is to get consistency with your own gear, and make any adjustments from there....

On a slightly more dificult conversion, is taking someones promash recipe and converting into beersmith (or vice verca). There are quite a few differences in the programming, the main one being, imo, in relation to the baseline calculation for the hopping.....promash uses whole hops as it's default, and makes adjustment for pellets; beersmith does it in the opposite direction, uses pellets as it's defaults, and adjusts for flowers. You wouldn't think that this makes much of a difference; but it does. Having crunched th numbers over a range of recipes, I've found that the overall utilisation in beersmith needs to be set to 111% hop utilisation factor, in order for the IBU to match point for point in identical recipes...(in other words, instead of 90% utilisation for flowers, you increase it to achieve an equivilency of 100%, ie 90% x111%). In the course of most "general" recipes, it doesn't make a hell of a lot of difference. What's a couple of IBU between friends when it's an APA with 40IBU to begin with? It's a small fraction......but when I went AG, I set myself a hard task, to force myself to conform to a certain degree of precision....that is, brewing Milds. The tolerences are much lower in a 1035/17IBU mild than they are in a 1050/40IBU APA. The small, seemingly insignificant differences, stick out like a third wossit on a dog....But, as said, the most important thing really is to get consistency on your own rig. The numbers themselves then become somewhat meaningless, because you are then aiming for the range that you want based on your own calculations, to your own experiences, on your own equipment. 

(actually, a good example of the IBU issue in beersmith can be seen in the recipe database, which afaik gives a result closer to that of promash. If you have a look at DrSmurtos recipes, it has the IBU that was calculated with the database software; in the notes, he has been kind enough to state what Beersmith gives as the IBU.......do a quick bit of math, and you see it's very close to 111% varience.)

Whoops....marginally OT. Sorry. B)


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## mckenry (13/4/09)

Screwtop said:


> Evaporation percentage rates don't work. Boiloff rate for my system is usually 6L per hour.
> 
> Screwy



Hey Screwy. See post #29, (mine above). I know they dont really work properly, but as far as beersmith goes, how else will I get my water volumes right? Do you think %s are OK if I always aim for the same post boil volume?
Thanks,
mckenry


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## flattop (13/4/09)

Oops i didn't include the trub in mine but i estimate the trub to be around 1/2 a litre, i whirlpooled the urn and the crown has an element cover in the center that all the trub material seemed to cling to, i was able to tilt and drain almost all the wort out.


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## crundle (14/4/09)

I lose around 7.6% per hour in my Crown urn with the lid off for the boil outside in Autumn. Not sure how it will change with the seasons but seem to think that it will. Probably aournd the same loss to trub as flattop at around 0.5-1 litre.

Crundle


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## raven19 (14/4/09)

Second AG, we lost 5L or 7% of preboil volume in a 60min boil.
Trub losses depend on amount of hops we use, as we tip the kettle to capture maximum wort possible without break/hops.


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## Fourstar (14/4/09)

approx 15% p/hour with around 1-1.5L of loss of trub in the kettle.. higher loss for flowers/plugs or a highly hopped beer 150g+ in 23L.


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## rich_lamb (14/4/09)

I'm still trying to figure out how using a % of kettle volume can possibly give me a relevant number (that can be used as a basis of comparison). I use a 50L kettle and consistently get evap loss of 4.5L/hr.
So that would be about 9%, which is kindof a pointless number since I typically boil about 24-27L or wort (closer to 20%).

I'd be far more interested in the absolute value; and it seems most people have been good enough to publish that. It might also be worth listing the kettle type to see if that affects the evap rate. Mine is a SS keggle, which I feel boils quite poorly, and I've often thought a big Ali pot would do a better job.


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## Thirsty Boy (15/4/09)

Screwtop said:


> Evaporation percentage rates don't work. Boiloff rate for my system is usually 6L per hour.
> 
> Screwy



Of course they do - they just aren't for what people think they are for.

The boil off rate in % is to let you know a bit about your level of boil vigor and to let you know whether you have atually evaporated enough to carry away all the volatiles etc that need to be gotten rid of.

Say I do a 25L batch and I boil off 2.7L per hour. Thats 11% of my starting volume and thats right in the middle of the rates that are accepted as being acceptable in order to ensure the quality of your beer.

Great - so now I want to make a batch starting with 45L - my kettle is a 50L keg - so it will fit. And I boil off 2.7L per hour. So I can do all my calculations and know I will get 42.3 at the end of the boil.

sweet - right?? So who the hell needs the % figures for boil off. They are obviously of no use to anyone and should be ignored

Except that now - if I do look at the % figure - I am only boiling off 6% of my starting volume - and there is a goodly chance that I will not have evaporated all the bad out of the beer. Its also possible that there wasn't enough heat in the system to give me a good hot break, or utilise my hops fully etc etc.

Now if I turned my burner up a bit higher - got the wort jumping around a bit more (which effectively increases the surface area) and managed to up that figure by a litre or so (up to 8%) - then I am back into the comfort zone of the generally accepted figures. Anyone who says you cant do it is full of the proverbial. A strong, very active boil will evaporate more than a gentler boil. Pot surface area is the _most_ important factor, but its not the only one.

So - different figures for different purposes. L/hr lets you do your numbers. Its about starting and finishing volumes.

% of starting volume per hour is about whether you L/hr figure is high enough in the first place (or maybe too high) - and whether you should consider changing something about your system to get your boil to a point where you know its doing everything it should be doing.


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## KHB (15/4/09)

I lose 5lt in boil off whether im doing a single or a double batch consistently.

Scotsman06


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## mckenry (15/4/09)

Thirsty Boy said:


> Of course they do - they just aren't for what people think they are for.
> 
> The boil off rate in % is to let you know a bit about your level of boil vigor and to let you know whether you have atually evaporated enough to carry away all the volatiles etc that need to be gotten rid of.
> 
> ...



Thanks Thirsty, That all makes good sense
But herein lies the problem for us new to Beersmith.
I know I boil off 9L per hour. I have a recipe for final volume of 35L. I know at my 21% figure I need to have a pre boil volume of 44L. Beersmith also works this out using my 21% figure.
As has been stated - 9L/h is constant.
As a test, I halved my final volume to 17.5L. I would want to have a preboil vol of 26.5L but beersmith works it out for me as 23.4L (roughly) based on 21%. So whats a beersmith newbie to do? Every time I change volumes do I need to untick the 'Set boil volume based on equipment' box and add 9L to the batch size and let beersmith work out the new sparge water volume for me? Is this the go? Or is there a way of setting 9L/h as the constant for beersmith formulations instead of the evap rate?
cheers for your help.
mckenry


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## Screwtop (15/4/09)

mckenry said:


> Thanks Thirsty, That all makes good sense
> But herein lies the problem for us new to Beersmith.
> I know I boil off 9L per hour. I have a recipe for final volume of 35L. I know at my 21% figure I need to have a pre boil volume of 44L. Beersmith also works this out using my 21% figure.
> As has been stated - 9L/h is constant.
> ...


mckenry, depends on which school you belong too, some don't advocate anything more than 5% boiloff rate so don't sweat this issue. Anyway my workaround in beersmith is to simply work with whatever pre-boil volume and adjust the percentage in Beersmith until the loss equals the known rate for my system.

Hope this helps,

Screwy


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## mckenry (15/4/09)

Screwtop said:


> mckenry, depends on which school you belong too, some don't advocate anything more than 5% boiloff rate so don't sweat this issue. Anyway my workaround in beersmith is to simply work with whatever pre-boil volume and adjust the percentage in Beersmith until the loss equals the known rate for my system.
> 
> Hope this helps,
> 
> Screwy



OK. Pity there isnt a section that you can check or uncheck the L/h or % evap for beersmith to work with to give you required water volumes.
Guess your way or my suggested way are just different ways of skinning the same cat.


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## peas_and_corn (7/5/10)

Bumping this thread instead of starting a new one.

In the most recent issue of BYO, Mr Wizard says that an evaporation rate of 20% is somewhat excessive. His reasoning is that it can make a beer darker than it should (if you're aiming at making something pale it can be an issue) and that it "is likely lending some flavours that would be good to not have".

So, do you agree with this claim? If so, what sort of flavours would be added in with an excessively high evaporation rate? What would I look for when drinking one of my beers that would indicate that the boil has a too high evaporation rate?


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## MarkBastard (7/5/10)

I wouldn't have a clue to be honest. I just now know what I need to start with to get 20L of wort in a cube.


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## Thirsty Boy (8/5/10)

Once again - its not the rate which is all that important in that argument - its the vigor of the boil. Mr wizard assumes that to get the 20% mentioned you are simply shoving in too much heat and so your boil is _too active_. You would be looking at darker beer, perhaps more malt and caramel type flavours. All OK in a robust type ale, not so much if you are looking for a delicate light lager type beer.

You can also potentially damage head formation, clarity and stability of your beer by boiling too hard - not to mention simply wasting a crapload of gas.

But thats all about boiling too hard - not about evaporation rate. Because as the rest of this thread mentions, the biggest influence on evaporation rate is pot surface area. So if you happen to have a low wide pot, or to be boiling your 20L batch in your 100L pot... then you _are_ probably getting a giant boil off rate, but you aren't _necessarily_ shoving in too much heat or boiling too hard. You probably are - but not necessarily. 

All the figures people quote (me included) generally assume you have a brew kettle _somewhere around_ the rough ideal of twice as wide as your wort will be deep. So for example - if your starting volume is 25L, then a brew pot with 40cm diameter is perfect. In a 40cm diameter pot the depth of wort for 25L is 20cm. So you have the 2:1 ratio. In that case, or close(ish) to it - the % boil off rates recommended, will match reasonable L/hr figures, will match good boil vigor.

So when people talk about boil off and evaporation - you need to keep that assumption in the back of your mind. It might not apply to you. Of course.. if it doesn't, you need to ask yourself if you have an appropriately sized pot?


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## Nick JD (8/5/10)

Depends a lot of whether I suddenly sit up off the couch and say, "SHIT! The homebrew."

And in the bottom of the pot is about 8 liters (started with twice that of 1.065) of really dark, half caramelised wort with a hop bag half-dangling off the side that's been boiling for about two and three quarter hours. 

Damn it if it didn't turn out to be an exceptional beer...


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