re: Gas types

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I guess it all depends on what kind of beer you like drinking. Since yeast naturally produces CO2 and most people start out bottling then the natural transition is to go for CO2 in your kegs. And since the only kind of beers that use "Beer Gas" are Brittish beers so that cuts down the choice down even further. I love Brit beers but I couldnt drink them all the time. Plus there are cheaper options to Nitro.

If you wanted to only have Brit beers then fair enough but here in Australia I would have to make a special trip to BOC or whoever and get the gas bottle filled, apart from all the trips I have to make to the LHBS which is a 35 min drive. A royal PITA if you ask me plus more money. I was lucky enough (maybe) to get some 2nd hand Brit pub taps (Celli). 2 of them have a thread on the end for a sparkler so Im going to try out the low PSI with a sparkler option.

I have also read on the interwebs that nitro beer gas is only a very rescent invention (20 or 30 years) when they tried to get rid of Real Ale. It was an attempt to mimick the Real Ale pour. I may have my info wrong but you get the idea. Apparently before the invention of the widget Guinness cans came with a syringe to get a nice foamy head. If you havnt tried the syringe method then you should. It takes a bit of practice to get the beer in glass to beer in syringe ratio but it works. Nitro is not really an authentic way to serve beer but then I guess CO2 isnt either.

Instead of frigin around with beer gas I would rather use a syringe with my brit ales on a low PSI than frig around with all other expensive gear. For that matter I would rather make a DIY beer engine. Actually I would love to make a DIY beer engine. My next winter beer project.

But if you are able to get a beer gas and CO2 setup happening then I would be extremly jealous

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Interesting read Josh.

I was curious, as pubs here in Australia do use the co2/nitrogen mixes for mass produced lagers etc. So it's not just an English ale/Guinness thing, the difference being the ratio between the 2 gases.


I think the bulk of it can be ascribed to the distances involved in a pub from the keg to the tap, the Nitrogen being under a higher pressure can do a better job of pushing beer, the CO2 component is there to do what we expect CO2 to do.

Therefore, not particularly relevant to homebrewing. (unless you were doing Guinness clones)

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Taking up PP's challenge... I'm no physict or chemist, I've had to sift through a lot of contradictory information. So please be easy on me for the bits where I'm wrong

I'll start this by unravelling the mystical Irish Stout and why Nitrogen is used.

Not Nitrogenated... like beer is carbonated. Nitrogen is relatively insoluble compared to CO2. These beers are carbonated, but dispensed under higher pressure with a Nitrogen/Co2 mix (beer gas) and using a special beer tap. Nitrogen fills up the headspace in the keg with enough pressure to dispense the beer through a restrictor plate, it's purpose is not to dissolve into the beer.

Restrictor plate... Beer is poured through the taps via a restrictor plate with small holes in it. By forcing the beer through these small holes, CO2 is forced to come out of suspension in tiny bubbles which is what you see in the foam. By comparison to an ordinary carbonated system, CO2 comes out of suspension in a glass of beer when it nucleates on imperfections in the glass. An ordinary glass of beer (not flat variety) has bubbles that are much bigger and find it much easier and quicker to pop on the surface of the beer.

Carbonated... Kegs in these systems are carbonated, with Beer gas used to pump it out. The beer gas used is 30% CO2 to 70% Nitrogen. The nitrogen is to push beer under pressure, the 30% CO2 is roughly the right amount to keep the dissolved CO2 in the beer in equilibrium with the head space (e.g. so it doesn't come out of the beer into the kegs headspace and vice versa so that CO2 doesnt go into the beer and overcarbonate). If CO2 alone were used to pump this beer, over time the amount of dissolved CO2 would increase and it would be overcarbonated for it's special style.

Not Sour... CO2 and water form carbonic acid, we perceive this as sour. There is a lower concentration of CO2 dissolved in a keg than in an ordinary draught beer, so it is only mildly carbonated. The amount of CO2 in the headspace is less than if it were a straight CO2 system, even though the total pressure is higher it is only 30% CO2 in the beergas mix, so the CO2 in the headspace will not increase the amount of dissolved CO2 in the beer.


Mystical Irish Stout at it's simplest.
1. Smaller bubbles of CO2 on pouring (from forcing beer through small holes in a disc) resulting in a smoother mouthfeel and longer lasting head
2. Carbonated rather than flat, but modestly (and therefore not sour)


But this isn't the only use of Nitrogen (i.e. 1 to form small CO2 bubbles and 2 to prevent overcarbonation). It also is useful for pumping beer in modern pub environments.


Liquid vs Gas... There is a fundamental difference between bottled nitrogen and CO2 at pub temperatures. CO2 is in liquid state in a bottle of CO2 - but nature abhors a vaccum, so an amount of Gas is in the headspace. As we keep using the gas tank, by emptying the gas in the headspace, gas comes out of liquid suspension to prevent a vaccum. Eventually, there will be no more liquid CO2 - in which case your tank will now start to run out of pressure quickly as you empty out what is now just all gaseous CO2 with no liquid reserve.

By comparison, Nitrogen at the temperature and pressure it's stored at in tanks in pubs will only be a gas.

To have a useable amount of Nitrogen, it's only in decent sized tanks and is in a much thicker steel bottle and requires a different regulator to withstand the pressure,

This is an advantage in modern pubs where they can have a lot of distance between the beer taps and the storage area for the kegs. The pressure of nitrogen gas can better push over the distance, but with a CO2 component to maintain a presence in the headspace of the kegs so that CO2 stays dissolved.

Depending on how much pressure is needed to push the beer, there are a range of beergas mixes with different ratios of the 2 gases.

Just a note: Liquid takes up a lot less space than gas,

There is more CO2 is in a tank of CO2 than is in a tank of Nitrogen due to the CO2 being liquid. There are 14 x 50L kegs from a 10kg bottle of straight CO2 compared to 6 kegs from a beergas mix in an equivalent sized tank that's 30% CO2 to 70% Nitrogen (more kegs where there is a higher CO2 component ratio).


Application to homebrew...

For normal beers, there is no reason to use bargas. You get less gas per tank and it is therefore more expensive. Maybe if you pushed beer further than a regular kegerator system you might start to consider it.

But if you want to create a small bubble beer... Please, this is hypothesis, someone who has done it - or will do it can feedback.

The simplest thing is to get a tap suited for nitrogen beers. They are low carbonated. To keep it as a CO2 system, crank the pressure up higher than you would for a normal brew to dispense it to overcome the resistance of the narrowed openings from the restrictor plate. Burp the keg when finished as leaving it with the higher pressure will result in the beer gradually overcarbonating. Just leaving it burped though, CO2 will come out of solution, so you will need to put a little pressure back into your keg.

Or... Buy a beergas cylinder/fittings. You can keep the pressure up, but with less CO2 present in the gasmix, you won't have the same issue of overcarbonating.

And a final word on it. Mystical Irish Stout is carbonated, but at a low level of carbonation. The 25% CO2/75% Nitrogen is the right proportion to keep the beer at the right level of carbonation. With a higher CO2 mix, a proportion will dissolve into the beer to keep the CO2 in the headspace and the CO2 in the beer in equilibrium, so it will overcarbonate for the style of beer. The reverse is also true, a regular beer on a 25% CO2 /75% Nitrogen mix will lose carbonation from the beer and it will become undercarbonated, you would want it in the range of 60% to 90% CO2 if using Bargas for a regularly carbonated beer. http://www.draughtquality.org/wp-conten" onclick="window.open(this.href);return false; ... 5-Gas1.pdf

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Great read that DanIam, will definately subscribe to any more info you can add.

Jayb240 - I'm not sure what you mean. Is this to carbonate with C02 to try and improve its diffusion, or to try and emulate the smaller bubbles seen with nitro?

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Fantastic info Dan .

I hope you are having fun researching it all. When you do tie it all up, please send me a PM and I'll make sure it doesn't get lost.

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Jayb240 wrote:Had an idea I'd like to float here........
What if I connected some silicon tubing to the Co2 Port on my corny keg and hung a airation stone to the other end?

I was thinking along the same lines, but just to a disk that I perforated a few times. Now take it with a grain of salt, this entire exercise is a thought exercise as I will be brewing and drinking Hashies spectacular old speckled hen clone for the next few months viewtopic.php?f=7&t=820

The first thing to come to mind is pressure of gas.

You will require more pressure to dispense and I haven't got a clue to the psi. So make sure that you burp the keg when you have finished your session, then maybe bring the pressure back up to a low level. If you fail to do so you will progressively overcarbonate your beer over time. Just burping the keg without bringing a little pressure up will lower the level of carbonation.

Maybe an aeration stone is just too fine and will require silly gas pressure? Possibly also just give you all foam even if you can get beer through it? (just guesses) But, without trying, it won't be known.

This is an example of a restrictor plate.
http://www.keystonehomebrew.com/shop/me" onclick="window.open(this.href);return false; ... rpns_1.jpg

Someone has to be first If you undertake this, maybe you can report back on how the airation stone went (if you go that method) and the pressures that worked for you.

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I don't know if the following helps with the thread, but this is an excerpt from a book I am currently reading (Bamforth - A Quality perspective, 2007).

Palliative options: of gas composition, widgets and other devices
Nitrogen vs. CO 2
While most beers are naturally and conventionally carbonated, the use of a portion of nitrogen gas has been shown to substantially improve foam stability. In part the benefit of nitrogen is that it has a lower partial pressure compared to CO2 , which results in the production of smaller bubbles (Carroll, 1979 ; Fisher et al., 1999 ). However, this physical characteristic of nitrogen makes the formation of bubbles less likely than with CO2 . Therefore nitrogen is typically used in conjunction with widgets (see next section) or as “bar gas” (typically 25% nitrogen, 75% CO2) for the draught dispense of beer via the delivery orifice that ensures the proper level of bubble formation. The smaller nitrogenated bubbles are also more stable because nitrogen has a lower aqueous solubility compared to CO2, leading to less gas diffusion and an inhibition of disproportionation ( Carroll, 1979 ; Mitani et al., 2002 ; Bamforth, 2004a ). The addition of nitrogen into the beer also changes the foam’s mouthfeel to a “creamy” texture, however the lower CO2 content leads to beer with less “prickle” (acidic and bubble collapse) on the palate ( Carroll, 1979 ) making the beer taste flat and watery. Other investigators have found that in comparing blind-folded with sighted judging of conventionally carbonated beers the visual impact of the foam head on a glass of beer is more important than the tactile impact on beer flavour and mouthfeel ( Langstaff and Lewis, 1993 ). Consequently, the acceptability of nitrogen as a palliative option will depend on the beer style and consumer preferences.


##EDIT##

I am still struggling to visualise the "airstone" scenario is this in the keg? outside for dispense? what is connected where?

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]

mally wrote: I am still struggling to visualise the "airstone" scenario is this in the keg? outside for dispense? what is connected where?

Outside the keg at the end of the beer line is what I presume. On/off valve somewhere? Will it spurt in all directions? The joys of scientific investigation

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re: Guinness cans and the widget.

This is from wiki.

"When the can is opened, the pressure in the can quickly drops, causing the pressurised gas and beer inside the widget to jet out from the hole. This agitation on the surrounding beer causes a chain reaction of bubble formation throughout the beer. The result, when the can is then poured out, is a surging mixture in the glass of very small gas bubbles and liquid."

Note that it is not saying that you get very small nitrogen bubbles as such, the Guinness cans are carbonated, the chain reaction of bubble formation is primarily the CO2.

I bring this up as there is a lot of reference to nitrogen bubbles throughout the quagmire of misinformation that is the internet. Of course, if I'm wrong, I'm adding to the misinformation

But I think it's just people taking a conclusion that nitrogen is pumped in and it therefore is nitrogen bubbles that is the effect, whereas the nitrogen is the cause (coupled with the restrictor plate) and not the effect.

I'll also note that the Guinness site itself mentions Nitrogen bubbles as if it's nitrogen that forms the head etc. So I'm putting myself right out there on this when I say it's all about small CO2 and that the Nitrogen is just for pressure. So, take everything I have said with a grain of salt and get proving one way or another.

My conclusions are based on internet reports of people doing this with straight CO2 to dispense and getting the head and cascade via a stout faucet and higher pressure to dispense, along with logic (which may be faulty). I'll put my money where my mouth is, but that won't be until I exhaust my current supplies of grain, before I get a stout faucet along with new grain due to zero available funds.

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