Pressure gauge mounted in bottle cap

passedpawn · Sep 11, 2011

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.

Chuckabrewski · Sep 11, 2011

I would like to see how this turns out keep me updated

strumke · Sep 11, 2011

You may be reading a little lower than what you want to know since the bottle will stretch a bit. May not be significant, but just a thought.

wyzazz · Sep 12, 2011

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.

passedpawn · Sep 12, 2011

wyzazz said:
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.

I considered that. The gauge above is just easier though.

Catt22 · Sep 12, 2011

wyzazz said:
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 · Sep 12, 2011

Catt22 said:
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 · Sep 12, 2011

horseinmay said:
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 · Sep 12, 2011

Catt22 said:
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 · Sep 12, 2011

wyzazz said:
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.

passedpawn · Sep 12, 2011

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.

passedpawn · Sep 12, 2011

horseinmay said:
Did you use teflon tape on the threads?

yes.

passedpawn · Sep 13, 2011

Up to 23 psi this morning. Maybe I put closer to a full tsp of sugar in there :drunk:

Catt22 · Sep 13, 2011

horseinmay said:
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 · Sep 13, 2011

Catt22 said:
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 · Sep 13, 2011

Catt22 said:
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 · Sep 13, 2011

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 · Sep 13, 2011

lincoln said:
*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 · Sep 13, 2011

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 · Sep 13, 2011

wyzazz said:
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.

horseinmay said:
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 · Sep 13, 2011

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

wyzazz · Sep 13, 2011

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

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 · Sep 13, 2011

ACESFULL said:
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 · Sep 13, 2011

Atl300zx said:
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 · Sep 13, 2011

Catt22 said:
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 · Sep 13, 2011

Atl300zx said:
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 · Sep 13, 2011

wyzazz said:
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.

passedpawn · Sep 13, 2011

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 · Sep 13, 2011

Catt22 said:
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 · Sep 13, 2011

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

Pressure gauge mounted in bottle cap

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