Pressure gauge mounted in bottle cap

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I saw someone else do this on here (a very long informative thread, couldn't find it). I was just bottling an octoberfest and I thought I'd give it a try. Anyone else do this?

I mounted the gauge into the cap with a rubber washer and nut. It's tight as hell, I'm pretty sure it'll hold pressure. I did it to know when the other bottles were carbed. Just for fun I guess, since I won't be drinking them anytime soon.

 

wyzazz

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Why not just put a tire valve stem in the cap? Then you could use a tire gauge to read the pressure whenever you want.
 

Catt22

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Why not just put a tire valve stem in the cap? Then you could use a tire gauge to read the pressure whenever you want.
Because it would be very difficult to take a reading without relieving some or all of the pressure using a tire gauge. I'm not convinced that there would be an advantage to using this method. The pressure in the head space will build up relatively quickly, but it takes some additional time for the gas to diffuse throughout the beer. My point is that a pressure reading alone may not accurately reflect the carb level of the beer. I do agree that it would be interesting to try just for fun.
 

horseinmay

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Because it would be very difficult to take a reading without relieving some or all of the pressure using a tire gauge. I'm not convinced that there would be an advantage to using this method. The pressure in the head space will build up relatively quickly, but it takes some additional time for the gas to diffuse throughout the beer. My point is that a pressure reading alone may not accurately reflect the carb level of the beer. I do agree that it would be interesting to try just for fun.

Actually, the pressure inside would be consistent throughout. The pressure would build up slowly by fermentation, and would diffuse in the beer as well as build up in the headspace. I dig this idea, and look forward to seeing how it turns out. Did you use teflon tape on the threads?
 

Catt22

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Actually, the pressure inside would be consistent throughout. The pressure would build up slowly by fermentation, and would diffuse in the beer as well as build up in the headspace. I dig this idea, and look forward to seeing how it turns out. Did you use teflon tape on the threads?
How long do you think it takes the yeast to consume the small amount of priming sugar at room temperature? I would think that would happen relatively fast.
 

wyzazz

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How long do you think it takes the yeast to consume the small amount of priming sugar at room temperature? I would think that would happen relatively fast.
Under pressure & in an alcoholic environment, it really depends on the beer, the temp & the state of the yeast. I've had some done in 5 days, others took 4 weeks.
 

horseinmay

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Under pressure & in an alcoholic environment, it really depends on the beer, the temp & the state of the yeast. I've had some done in 5 days, others took 4 weeks.
Sounds about right. It doesn't matter, as far as pressure is concerned. There is equilibrium inside the bottle. The headspace is exerting pressure on the top of the fluid, keeping the bubbles in solution. The pressure is equal in the headspace and within the fluid itself. Just make sure to chill the bottle before opening it, so you don't get a geyser.
 
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I bottled using about half teaspoon of sugar in that 16.9oz bottle.

The ocfest was at 32F when I bottled. Probably 40-50 by the time I got the cap on.

Within a couple of hours it was reading 5 psi (see pic above).

This morning it was at 10 psi.
 

Catt22

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Sounds about right. It doesn't matter, as far as pressure is concerned. There is equilibrium inside the bottle. The headspace is exerting pressure on the top of the fluid, keeping the bubbles in solution. The pressure is equal in the headspace and within the fluid itself. Just make sure to chill the bottle before opening it, so you don't get a geyser.
Passedpawn reported that the gauge is up to 23 psi already after only about two days or so. If what you say regarding the instant equilibrium is accurate, the beer is now carbonated with about 2 volumes of CO2 in solution. Two volumes would be an acceptable level for a Porter or Stout. Should be nearly ready to drink by the end of the day. Looks like many of us have been wasting a lot of time waiting 2 or 3 weeks to bottle condition our beers. That's nearly as fast as force carbing a keg. Amazing!
 

ACESFULL

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Passedpawn reported that the gauge is up to 23 psi already after only about two days or so. If what you say regarding the instant equilibrium is accurate, the beer is now carbonated with about 2 volumes of CO2 in solution. Two volumes would be an acceptable level for a Porter or Stout. Should be nearly ready to drink by the end of the day. Looks like many of us have been wasting a lot of time waiting 2 or 3 weeks to bottle condition our beers. That's nearly as fast as force carbing a keg. Amazing!
I would be curious to see what the beer tastes and pours like that. I am guessing that the potential of extra sugar might have caused the pressure to build quicker. Not only that but the head space maybe 23 psi but has that CO2 been forced back into the solution?? That is the question. If so this is an ingenious idea.
 

wyzazz

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Passedpawn reported that the gauge is up to 23 psi already after only about two days or so. If what you say regarding the instant equilibrium is accurate, the beer is now carbonated with about 2 volumes of CO2 in solution. Two volumes would be an acceptable level for a Porter or Stout. Should be nearly ready to drink by the end of the day. Looks like many of us have been wasting a lot of time waiting 2 or 3 weeks to bottle condition our beers. That's nearly as fast as force carbing a keg. Amazing!
Just because the pressure is at equilibrium throughout the bottle doesn't mean that the CO2 has been forced in to the liquid just yet. That process is called diffusion (sometimes confused with osmosis) and takes some time at higher temperatures.
 

lincoln

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ummm, didn't the co2 start out in the liquid? how much yeast is in your head space? :drunk:


*edit* Would shaking a couple at that psi have the same effect as shaking a keg to force carbonate it?
 

ChandlerBang

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*edit* Would shaking a couple at that psi have the same effect as shaking a keg to force carbonate it?
When you force carb a keg you either leave it hooked up to the gas or hook it back up as soon as you are done rolling it on the floor. Thereby replacing the CO2 that left the headspace and entered the solution during agitation. So, short answer is I don't think so? Then again I'm in the set it and forget it camp.
 

Cazamodo

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I'd like to see this how this all works out. I pasteurise my ciders that I bottle, and it would be great to try and work out a way of checking carbonation without having to open a new bottle each time. Especially in my experiment 1 Gal batches. Then I would know when I'm at my carb level to kill the yeast off.
 

AnOldUR

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Just because the pressure is at equilibrium throughout the bottle doesn't mean that the CO2 has been forced in to the liquid just yet. That process is called diffusion (sometimes confused with osmosis) and takes some time at higher temperatures.
It doesn't matter, as far as pressure is concerned. There is equilibrium inside the bottle. The headspace is exerting pressure on the top of the fluid, keeping the bubbles in solution. The pressure is equal in the headspace and within the fluid itself.
Pretty sure that wyzazz is the correct one here. Someone else did an experiment similar to this. The pressure in the head space went up and then settled as the CO2 was absorbed into the beer. Something about the fermentation producing CO2, but it takes time to diffuse into the liquid. When it's first produced it moves up into the head space, but doesn't instantly get absorbed.

If you've ever used Carbonator Caps, you'd know that you can put 30psi into a PET bottle and the bottle is rock hard. Shake it up and that CO2 in the head space absorbs and the bottle softens. You do the shake thing to get quick results, but the same thing would happen if you let it sit. It would just take longer. Higher pressure at first, then lower as the CO2 goes into solution.
 

Atl300zx

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also what effect does the fact that it is room temp versus chilled have the pressure?
 

wyzazz

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ummm, didn't the co2 start out in the liquid? how much yeast is in your head space? :drunk:
It was created in the liquid but it's also lighter than the liquid, gravity works faster than diffusion so it rises in to the headspace, over time the CO2 will try and find it's "happy place" and become evenly distributed throughout the liquid and the headspace. The liquid can more readily accept CO2 (or any gas for that matter) when it's colder, that's why it's recommended to chill your beer for at least 24 hours before consuming. It makes for a better carbonated beer when all is said and done.
 

Catt22

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I would be curious to see what the beer tastes and pours like that. I am guessing that the potential of extra sugar might have caused the pressure to build quicker. Not only that but the head space maybe 23 psi but has that CO2 been forced back into the solution?? That is the question. If so this is an ingenious idea.
Actually, that was precisely my entire point. The yeast will consume the priming sugar relatively quickly and the bulk of the CO2 will accumulate in the head space. It will take some time for the gas to dissolve into the beer. This is why we typically anticipate a 2-3 week wait before chilling and pouring. My point is that monitoring the head space pressure won't tell you a whole lot other than that the yeast is still active or not. You would still need to wait the two or three weeks before the beer would be considered fully carbonated even though the yeast finished their job very early on.
 

wyzazz

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also what effect does the fact that it is room temp versus chilled have the pressure?
Pressure drops as the temperature drops, likewise it will increase as the temperature increases. But the pressure will remain constant relative to the temperature.
 

wyzazz

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Actually, that was precisely my entire point. The yeast will consume the priming sugar relatively quickly and the bulk of the CO2 will accumulate in the head space. It will take some time for the gas to dissolve into the beer. This is why we typically anticipate a 2-3 week wait before chilling and pouring. My point is that monitoring the head space pressure won't tell you a whole lot other than that the yeast is still active or not. You would still need to wait the two or three weeks before the beer would be considered fully carbonated even though the yeast finished their job very early on.
Still, I find it an interesting little experiment/observation. You get to see how quickly (at a given temp) the yeast will consume all the priming sugar.
 

Catt22

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also what effect does the fact that it is room temp versus chilled have the pressure?
Google "beer carbonation chart". The beer will absorb a specific volume of CO2 at a specific temperature. This is the reason we typically maintain a constant serving pressure and temperature for kegged beer. Varying the temp or pressure will alter the carbonation level. It doesn't happen instantly, but can take some time to reach the new equilibrium state.
 

Catt22

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Still, I find it an interesting little experiment/observation. You get to see how quickly (at a given temp) the yeast will consume all the priming sugar.
Yeah, I think I already said that as well.
 
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It'll be interesting to watch the needle drop when I put it in the fridge (maybe this upcoming wkend).

I'll take before / after pics. It'll just confirm what the carb charts show, but interesting nonetheless.
 

AnOldUR

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My point is that monitoring the head space pressure won't tell you a whole lot other than that the yeast is still active or not.
My thought is that it will tell you that the yeast was active, not that it is "still" active. Also, the gauge should give you an idea when the beer is done carbonating. After peaking, the reading should drop. When this dropping stops and stabilizes the beer should be fully carbed. No?
 

wyzazz

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I think I'm just jealous that I don't have a gauge on any of my bottle caps. ;)
 

Catt22

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My thought is that it will tell you that the yeast was active, not that it is "still" active. Also, the gauge should give you an idea when the beer is done carbonating. After peaking, the reading should drop. When this dropping stops and stabilizes the beer should be fully carbed. No?
Yes, active as in present and alive. Yep, I would say that when the pressure stops dropping the beer should be fully carbed which should take about 2-3 weeks under normal circumstances. I've never had a beer fail to carbonate in the bottle and only rarely has any been fully carbonated in less than two weeks. Again, putting a gauge on a bottle would be interesting to observe, but that's about all it would be for me.
 

RDWHAHB

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Just because the pressure is at equilibrium throughout the bottle doesn't mean that the CO2 has been forced in to the liquid just yet. That process is called diffusion (sometimes confused with osmosis) and takes some time at higher temperatures.
Equilibrium is the result of diffusion.
 
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Alright, I put it back into the fridge, chilled, and served.

It was not fully carbonated. The body did have some moderate carbonation, but there was not enough there to lift a head on the pour.

The good news is that my octoberfest is EXCELLENT! I'm pretty happy about this because I donated a keg of it to a local festival on Saturday.

This has been an interesting experiment in understanding the way CO2 is created and absorbed by the yeast & beer. I intend on doing this with every batch I bottle. I'll be more patient with the next batch.

Cheers! :mug:
 

kenc_zymurgy

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Very interesting.

If I understand this correctly, it seems that in some cases yeast can produce CO2 faster than the beer will absorb it. Many of us bottle a sample in a PET bottle to monitor carbonation - so this can tell us that the yeast is working, but it could take a bit longer for that CO2 to fully carbonate the beer. That seems to match my experiences also, when I notice that the bottle gets firm within a few days, but after a week, the carbonation does not seem complete. But a week later it is much better.

Related questions:

If a sealed beer has stabilized at room temperature and high pressure (say 68F, 28PSI = 2.5 volumes), and it is quickly chilled to 36F, should we expect to see the pressure (still sealed - no external CO2 feed) reduce to 10 PSI (the same 2.5 volumes @ 36F)? And does it take any time for this to settle in (assuming the temperature has stabilized)? I don't think there is any CO2 moving between the head space and the beer - in each case the pressure/volumes are stable, right? So I don't think it should take any time. And I don't think the amount of head space should affect this either. But I don't know for sure.

My experience with mini-kegs with a tap set-up (where I can easily measure the pressure) seems to follow this, the pressure drop from room (naturally or force carbed) to chilled follows the charts.

-kenc
 

venquessa

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Interesting thread.

Found this:
http://www.deep-six.com/page70.htm

Strangely it's written for scuba divers, but answers a lot of questions about pressure, temp and transfer of gas to and from liquids.

In particular:
""Henry's law: A gas over a liquid will flow into the liquid until the pressure is equal. If you covered a lake with neon, the atoms of that gas would pass though the surface of the water until the neon in the water had the same pressure as what is left in the air. ""
 

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Sorry for bringing this thread back to life but I think it's worth talking about more. It seems that quite a few people think that a yeast-initiated carbonation in the bottle causes the headspace to pressurize with more CO2 molecules than are initially dissolved in the beer from the metabolism of the sugars. I think this is an issue of mixing concepts we learn from the application of external CO2 in a force carbonation situation.

First, keep in mind that in a closed system of liquid and co2, the concentration of CO2 will always seek equilibrium. The transfer from an area of higher concentration to lower is a result of diffusion. Yes, I do agree that the process can take a little time (dependent on a couple different factors).

In a force carb situation, the concentration of CO2 in the beer is generally low (it depends on what temperature the beer was fermented at as well as what temperature it was subsequently warmed to while still in an open container (airlocks count since gas can escape).

Think of it this way: The beer is essentially generating CO2 in the carboy and it has to push against the ambient atmosphere to escape through the airlock. At sea level, that's about 14psi. If you fermented the beer at a rock solid 70F, when fermentation is done, the dissolved CO2 is approximately .7 volumes before you do anything else. In other words, as it was fermenting, the beer AND the headspace were sitting at 14psi or 1ATM and .7 volumes of CO2 cannot escape from the beer. In reality, the concentration in the beer will be a bit higher than the headspace because it's actively being generated and that's why a bubble forms and rises to the surface. When fermentation is over, eventually all the excess CO2 in the beer will equalized to the headspace resulting in .7 volumes dissolved.

Now you take that beer, transfer it to a bottle, add sugar, and seal the cap. Now the ambient 1ATM of pressure is irrelevant. We're in a closed system. As yeast metabolize the sugar and create CO2, the concentration of CO2 in the beer is immediately higher than that of the headspace, let's say .8 volumes... diffusion is about to make the headpace equal and so on. In no way would the headspace ever have a higher concentration of CO2 than the beer in which it originated. The yeast don't swim to the surface to fart.

One last side note that isn't really on topic, but perhaps interesting anyway. If you have a beer in a carboy that is done actively fermenting, the CO2 concentration in the beer and in the headspace will eventually equilibrate to the concentration of CO2 in the area it's sitting in. For all intents and purposes, it's the concentration of earth's atmosphere (.0387% by volume). This sort of blows people's minds because you think, how can CO2 get past the water in the airlock? It diffuses into the water, then it diffuses out on the other side. Oxygen and nitrogen do the same thing in the opposite direction. The water just slows it down.
 

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Ever since I switched to 1/2 liter swing-top bottles, I've been having trouble with over carbonation and gushering, even after 2months in the bottle.I'm beginning to think I'm not leaving enough head space. With 12 oz. bottles, I would just use the displacement of the bottling wand to set the correct headspace. Does that work with larger bottles or should I leave a bit more?
 
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