Head at the end of the keg

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Yob

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Why is it better right at the end? The extra age? The extra pressure on a small volume?

I dont have head issues, always happy with retention and general foam quality, I just notice that as a keg is ending, its always fantastic.. and an indicator that the bastard is about to blow ... just wondering if there is a science behind why and if anyone has noticed this too.. never seen it posted so.. ideas?

also.. not happy that my Pliny is starting to display these characteristics...

waaaaa
 

OneEye

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Complete thread disrail, sorry, but did you NC your Pliny Yob?
 

Yob

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it was a swap brew.. I NC'd the arse off it.. I think it was the last to be fermented of all of them.. I saved most of the dry hopping to the keg too.. but faark did I keg hop it... :icon_drool2:
 

Jerry

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Noticed it as well Yob.

The last schooner or two always seem to be the best; both taste and appearance.

Sometimes you just know when it's imminent.

Never noticed the retention side but wouldn't surprise me.

Scott
 

Yob

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Pity a few of the more scientific posters are not on here these days..

Ive listened/read lots of things relating to foam/head retention in the actual beer itself, most of all of my beers contain a wheat component, I step mash as a matter of course.. Im not at all dissapointed with my general head from my beers, great lacing etc.. I just notice that toward the end of the keg its.. you know.. better.. there must be a reason..

Im going to get me some Bamforth books for my library but in all Ive listened to/read Ive not heard/read this aspect discussed..


also.. whats a schooner ;)
 

Jerry

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Yob said:
Pity a few of the more scientific posters are not on here these days..

Ive listened/read lots of things relating to foam/head retention in the actual beer itself, most of all of my beers contain a wheat component, I step mash as a matter of course.. Im not at all dissapointed with my general head from my beers, great lacing etc.. I just notice that toward the end of the keg its.. you know.. better.. there must be a reason..

Im going to get me some Bamforth books for my library but in all Ive listened to/read Ive not heard/read this aspect discussed..


also.. whats a schooner ;)
Sorry, science aint me strong point.

Schooner?

425ml. Part way between a thimble (pot) and a bucket (pint)

A happy medium.

Less thinking, more drinking. :)
 

MastersBrewery

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It may well be that by the end of the keg the beer is more carbonated from having been under pressure longer
 

Yob

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considered that.. doesnt seem to fit the bill with kegs that have sat there while Im demolishing ones like Pliny though.. it's a characteristic that fits all ending kegs..

Im almost certain it has something to do with liquid volume and the pressure differential or some such bullshit..

Smurto? MHB? Thirsty? ...
 

Jerry

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MastersBrewery said:
It may well be that by the end of the keg the beer is more carbonated from having been under pressure longer
Over carbonation tends to hamper retention though. Big head but no retention.

Yob's probably right, there will be a science reason.

It's after 1.00am, I aint science focused, and I'm a little pissed.

Just enjoy the last schooner....... or whatever you drink.....
 

Maheel

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i got a keg about to blow i reckon
it's the last keg in the fridge...
it's looking, pouring and tasting great....
i know it must be nearly empty.. only 1 or 2 pints left...
and i am dreading the rush of gas at the end :(

best thing to do is to have nice 6 pack in the fridge so when it blows you can crack a beer and toast the empty keg gods
thats my plan for later today :)
 

Coalminer

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I have also noticed that Yob - the last 1/4 of a keg

I have always assumed that it might be to do with the extra ageing or being carbonated longer
 

Edak

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I too have noticed this phenomenon, though I am sorry I can't contribute to the reason it happens. I have two kegs doing this at the moment and don't want then to blow!
 

TSMill

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Maybe try only 1/4 filling a keg and see how it goes from day 1.
 

yum beer

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I think the answer is not science...its spiritual/universal, your inner self 'knows' the keg is coming to an end and tricks your mind into believing that said remaining liquid is somehow turning into a mystical liquid gold....everything a beer should be, all the good things, for a final run of enjoyment before that unavoidable sinking feeling of despair when it blows. God giveth and God taketh away.

Or there could be a logical scientific reason.
 

Tropico

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1. It may be the beer draws faster into the dip tube, but normally through line and tap, as there is less beer from the bottom of the dip tube to the top of the beer.

2. Greater height from top of beer in keg to tap.

or most likely

3. The great disappoint in holding that last beer and knowing the keg is empty. Edit: see previous post by "yum beer"
 

verysupple

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It might have something to do with the balance of the system changing, but I don't know much about that as I don't keg.

My bet is that it's just a time thing. I'm guessing you don't filter? If that's the case, then even though a beer looks crystal clear at the start of the keg there are still small particles dropping to the bottom (the bigger heavier ones drop faster, obviously). By the end of the keg there are far fewer of these tiny particles in suspension so there are fewer, and smaller, nucleation points for the bubbles to form on. This means the CO2 is released from the beer slower and more consistently and helps keep the head intact.

Although I'd be inclined to try TSMill's idea to find out if it is a pressure/balance thing.
 

QldKev

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verysupple said:
It might have something to do with the balance of the system changing, but I don't know much about that as I don't keg.

My bet is that it's just a time thing. I'm guessing you don't filter? If that's the case, then even though a beer looks crystal clear at the start of the keg there are still small particles dropping to the bottom (the bigger heavier ones drop faster, obviously). By the end of the keg there are far fewer of these tiny particles in suspension so there are fewer, and smaller, nucleation points for the bubbles to form on. This means the CO2 is released from the beer slower and more consistently and helps keep the head intact.

Although I'd be inclined to try TSMill's idea to find out if it is a pressure/balance thing.
I've always thought it to be related back to clarification as you mentioned. Less nucleation points means less of a foam up and more residual CO2 in solution to aid in the head retention.
 

MHB

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Ok as it would appear that (sadly) Thirsty and the good doctor aren’t posting any more
There are two major factors at play, Condition and Maturation
Maturation takes time; it’s different for every style of beer and varies according to the storage conditions.
The science of maturation is very complex but can be broken down into a couple of rules of thumb that might help, these are generalisations and there will be exceptions. Most notably Hefeweizen, the banana flavour is very unstable and drops off rapidly so they tend to be best young. American style hop bombs, where the main focus is the hops, again they drop off fairly fast and you aren’t really drinking them for their malt or yeast flavours so they tend to peak fairly early.
Rules of thumb: -
Beer matures better in larger volumes. Not faster
Beer matures better colder, but it takes longer
The bigger the beer (higher O.G.) and the darker, the more it benefits from longer maturation.

Fully mature beer can (and will) taste very different if the condition (amount of dissolved CO2) is wrong for the style.
To understand condition you need to understand equilibrium put simply; at any given temperature and pressure there will be an exact amount of dissolved CO2.
Increasing amounts of carbonation will make the beer more acidic, increase the prickle on the tongue (this changes your perception of flavours), lift more aromas out of the beer; reduce the apparent malt flavours and body of the beer.
As a general rule the bigger and darker a beer the lower the desired carbonation, again with exceptions notably some Belgian styles.
If you visit Braukaiser you can find the equation and at the foot of the tables a rough guide to ideal levels of dissolved CO2 for common styles. This can vary from 3 to 9g/L of dissolved CO2 at a serving temperature of 4oC this is a pressure range of roughly 10-225kPa. The idea that one pressure suits all beer styles is to say the least misguided.
From a practical point of view where it gets very interesting is in a domestic fridge there can be (due to thermal layering) a 5oC difference between the top and the bottom of a keg, if you were serving at 70kPa and the bottom of the fridge was at 2oC the top of the keg could be at 7oC the amount of dissolved CO2 could vary by 0.8g/L, more than enough to make a significant difference to the taste of the beer.
The answer is to put a small fan (old computer fan) into the fridge to break up the thermal layering, so that the temperature is the same throughout, which of coarse doesn’t address the question of maturity, and to serve the beer at the appropriate temperature and pressure for the style.
It is important to have a good quality stable regulator, there are lots of cheap ones on the market that I wouldn’t trust my beer with.
What is probably happening is, as the keg gets lower the temperature of the beer is falling and the dissolved CO2 is increasing, and odds on the beer is actually maturing and it is in fact ready to drink. If the last glass tasted best, you probably started drinking the beer too soon.

Mark
For some reason I can’t insert hyperlinks so for the carbonation tables http://braukaiser.com/wiki/index.php?title=Carbonation_Tables
PS – for those unable/unwilling to embrace metric 1 Vol is about 2g/L of dissolved CO2, 100kPa is roughly 1 Bar or 14PSI. g/L is a better way to look at dissolved CO2.
 

Yob

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Nice, thanks Mark..

I'll generally aim for 3 weeks conditioning time... Unless I've run low, but I like the point you've made on the thermal layering, time to get that fan in place.

Cheers
 

Kiwimike

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Interesting to read Mark's obviously well informed post, I had been told that one of the benefits of kegging was that the beer stayed the same throughout - as opposed to a bottle maturing over time through secondary. It would appear that what I was told was incorrect.

I have also noticed the same extra head near the end of the keg and sometimes disconnect the gasline to compensate, but not sure about the taste difference.
 
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