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Desired Boiling Loss

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gryphonkd

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Hi All,

This might be a bit of a fundamental question; but how vigorously should one boil? and what is the reason?
I ask this because, I usually get the kettle up to the boil, and then use an 'analogue' power control to the element to keep the kettle on a gentle rolling boil for the hour. I only lose about 1 litre (approx 35L batch)
In fact even if i run it with the lid off and the element driving a furious boil, i barely lose much more than that - but the initial boil up cakes my hops all over the sides of the kettle - which i figure is somewhat of a waste, as they are no longer in solution.

What's the consensus - are people driving furious boils many to reduce the wort down to desired volume and OG?
If i'm happy with the pre-boil OG, surely I want to conserve as much wort as possible?
I am noticing most people boil off 4-8litres! seems excessive -- or is there another reason? does the boil process need to be vigorous for some other reason I am not aware of?

Thanks.
 

Truman42

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If your only losing 1 litre over your entire 60 min boil then my guess is that you have it on a simmer rather than a boil. Because I (Like many) will easily lose 4-6 litres over a 90 minute boil and I would consider my boil to be a gentle rolling boil.
I think NickJD decribed it well in his 20 litre stovetop BIAb thread that it should look like Rotarua. A gentle rolling of the wort bubbling at the surface and turning the wort over. Not bubbles popping at the suface like a vigoruous kettle boiling water.
But also not where the bubbles just reach the surface and barely move the surface of the wort.

I use a 40 litre crown urn with concelead element and set it at 100 and it gives me what I consider to be a sutiable boil vigour.

Were not trying to boil off 6 litres over the boil length on purpose, its just what happens to evaporate off over a 90 min boil like it or not.

Your not covering your boil kettle with a lid by any chance are you? Because you shouldnt be and thats the only other way I could see a loss of only 1 litre.
 

gryphonkd

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I do have the lid covered most of the time - i take it this is a 'no-no' ?
 

Crusty

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gryphonkd said:
Hi All,

This might be a bit of a fundamental question; but how vigorously should one boil? and what is the reason?
I ask this because, I usually get the kettle up to the boil, and then use an 'analogue' power control to the element to keep the kettle on a gentle rolling boil for the hour. I only lose about 1 litre (approx 35L batch)
In fact even if i run it with the lid off and the element driving a furious boil, i barely lose much more than that - but the initial boil up cakes my hops all over the sides of the kettle - which i figure is somewhat of a waste, as they are no longer in solution.

What's the consensus - are people driving furious boils many to reduce the wort down to desired volume and OG?
If i'm happy with the pre-boil OG, surely I want to conserve as much wort as possible?
I am noticing most people boil off 4-8litres! seems excessive -- or is there another reason? does the boil process need to be vigorous for some other reason I am not aware of?

Thanks.
Something not right there.
I use a Crown exposed element urn & I lose 10% to boil off, approx 3 litres. The urn boil is quite gentle compared to the raging lava boil I used to do with my 32jet Mongolian burner. There's really no need to boil off any more than 10% of your starting boil volume. Your boil is not vigorous enough if you are only losing 1 litre.
It seems that you are not using enough strike water or sparge water to get you to your starting boil volume after grain absorption etc.
Get that lid off.
 

Truman42

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gryphonkd said:
I do have the lid covered most of the time - i take it this is a 'no-no' ?
A definite no no and that explains why your only losing 1 litre during the boil. You need to keep the lid off so off flavours and compounds can evaporate out.
 

Nick JD

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Your boil vigor depends on the heat you apply to a large extent, but it also depends on the ratio of your kettle's width to height - and most importantly, your kettle's volume.

I boil reasonably sedately, yet my starting volume is 14L and my end volume is 10-11L. This is a HUGE boil loss and affects the final colour of the beer, the development of malty flavours (for the better IMO) and the ejection of DMS (creamed corn flavours more prevalent in light pilsner malts).

It's all about surface to volume ratios. In the same way it's much, much quicker to peel large potatoes, and the reason why bacteria are not 1 foot across, surface to volume ratios control a lot.

So if you have a big kettle, to achieve a desirable eveporation loss you need to apply more energy. Or boil in a wide, shallow kettle. If you make small batches, sometimes you need to reduce your boil vigor right down to a lame simmer and still lose 30% in an hour.

End of the day, DMS is why we boil hard. If you're not using Pilsner malt, and not getting corn flavours, experiment with boil vigour - you might just be wasting energy.
 

gryphonkd

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A very detailed article Truman.
Considering the flavour profile aspect only, looking at Figure 2 in the article, it appears that a boil loss of 2-3% (in my case, 3% would be 1 litre from a 35L batch) is ideal for reducing sulphur and grassy flavours , while preserving fruity flavours. Maybe it's not that simple?

I'm also using a 40L crown electric urn with exposed element. I had been playing with the thermostat but it's all over the place; a 3-5degree oscillation to avoid it being continuously powered, and then fighting boil overs when it is on.
I've solved the problem by putting a power control inline, so i can leave the element on 100% of the time, but finely control the power being delivered to the element. It takes 1400W normally, but once up to boil, i sustain it at about 600W.
This allows for a continuous, gentle boil, without boilovers. And even with the lid off, i'm still only losing about a 1-2 litres at the most. Temp stays at 99-100degrees.

My boilng surface area(m2)/volume(L) would be about 0.01 for a 20L batch and 0.005 for my max 40L batch. -- values I expect would be typical for most home kettles.
It seems that perhaps higher boil loss is either mainly performed to reach desired OG, where there has been an abundance of hot liqor required to get desired extract; Or a consequence of inadequate control over the heat source.
 

Diesel80

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gryphonkd, how full is your urn when you bring it up to the boil?

I would imagine for a normal 20-23L batch it should start somewhere about 26-29L preboil volume.
This would equate to somewhere about 10% boil off rate, which is pretty much in the target ballpark.

If you are boiling 35L i would imagine you would be looking to end up about 30-31L in volume.

I would boil harder mate.

At what point are you battling boil overs and what is the basis of your brewing (extract or AG?).

A squirty bottle of tap water will sort out the boil overs, as it starts rumbling, squirt it with a fine mist. keeps them under control.
OR boil less volume.

Cheers,
D80
 

black_labb

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Without the lid on you will want to be boiling with 1800 watts if not higher. you wont need the power control
 

QldKev

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black_labb said:
Without the lid on you will want to be boiling with 1800 watts if not higher. you wont need the power control
The old rule or thumb is 10-15% boil off, and no lid.
 

Thirsty Boy

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That article is a good simple explanation of the function of wort boiling - I'm not sure how you came up with 3% as an appropriate figure though. Thats to achieve most of the result for some of the criteria. 3% is not enough.

Read further and you'll notice that the article states that modern kettles tend to run at between 5 and 9% - you dont have a modern kettle, you have an electric element at the bottom of a pot. 9 at the lower end and probably ideally a little more is what you should be looking for.

In a simple kettle like the vast majority of homebrewers (including you) use, you want to be boiling off 8-15% of your starting volume, per hour. That is going to put you in the nice safe zone where you can be confident that you have shoved in enough energy to do everything that needs to get done in a boil, bit you aren't jamming in so much energy that you'll notice any of the ill effects that come with boiling too hard.

You are using a very common bit of homebrew equipment - one that if you just use it like everyone else does, will almost certainly give you results nicely inside the desirable range. Lid off - urn on flat out.

Nothing you have described says that you have a unique situation.... so I cant see why you need a unique solution. Just do what demonstrably works for everyone else.
 

KaiTroester

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I want to 2nd Thirsty's comment. Don't take boil-off advice from commercial (especially large commercial) brewers. They want to minimize that boil-off since boiling off water costs energy. They can get away with only 4% or less boil-off since their kettle designs and post boil wort stripping is able to remove enough DMS even with such a low boil-off. With a simple open kettle like ours you need closer to 10%/hr boil-off to remove the DMS. But more than 15%/hr are not needed and if you boil off that much you may actually do some harm due to the higher thermal loading of your wort.

Kai
 

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