Pressure gauge mounted in bottle cap

[dbsmith]

I don't know why you would suggest that shaking in a closed system disrupts equilibrium. Le Châtelier's Principle requires that you change something like temperature, pressure or concentration. Shaking does none of this.

Pressure is changing when the bottle is shaken. It is obvious because the walls of the container become harder to move, because there are more molecules of gas in the headspace colliding against the container's walls. I don't see what more evidence you need. Given time, equilibrium will become reestablished and the container will return to the original hardness.

I think that your assumption of a closed system is a false premise. Closing something off in a bottle doesn't shut the system off from the universe, as I can shake it, heat it, pass light through it, make gas come out of solution, etc. As CO2 leaves solution, the concentration has changed, and thus the equilibrium shifts.

Look at the graphs above. See the dip off in pressure? That indicates that at some point in time the pressure was higher than the pressure at equilibrium. That is because initially the yeast were producing CO2 in solution (reactants). This causes the reaction to shift to create more products. After the yeast have ceased making reactants, the reaction shifts back towards creation of the reactants (because of the excess products that were made earlier..indicated by the beginning of the 'dip'), and eventually equilibrium is reached (meaning that the creation of reactants and products is happening at the same rate).

 

[Hex23]

Pressure is changing when the bottle is shaken. It is obvious because the walls of the container become harder to move, because there are more molecules of gas in the headspace colliding against the container's walls. I don't see what more evidence you need. Given time, equilibrium will become reestablished and the container will return to the original hardness. I think that your assumption of a closed system is a false premise. Closing something off in a bottle doesn't shut the system off from the universe, as I can shake it, heat it, pass light through it, make gas come out of solution, etc. As CO2 leaves solution, the concentration has changed, and thus the equilibrium shifts.

When I first saw this discussion, I tried this out, and I have to say that I did not notice any change in pressure by feel in a 16 oz pop bottle. It wouldn't be too hard to use measurement system like this to see if there is any pressure change from shaking.

 

[Bobby_M]

OK, trial 3 is finally done. It turned out to be a pretty tasty beer too! (afterall, this really is still about making beer) It started as a Goose Island Mild Winter clone, but I decided to add a little more rye than normally recommended. I tastes nice, but I know I wouldn't add any more rye than I did.

Anyway about the experiment. I built an entirely new cap/bulkhead to try to eliminate the leak issue:

View attachment 97711

I pressure tested it to 49 PSI for about 2 days and it didn't appear to leak at all:

View attachment 97707

The priming was carried out in my fermentation chamber at around 70 F for 3 weeks. It does look like the pressure built to a plateau of 39 PSI and then diminished to settle at 35 PSI. The priming sugar amount should have put this at 2 volumes. At 72 F (as measured) that should have make a pressure of about 23 PSI at equilibrium. This is obviously well above that.

View attachment 97708

View attachment 97709

This is an excellent effort. Did you ever explain where the temp probe was? I still think that the spike may be influenced by temperature or some other anomaly. I was searching for the thread that showed anoldUR's similar experiment and he didn't get the spike. It would be nice to figure out they the results vary.

 

[Bobby_M]

Pressure is changing when the bottle is shaken. It is obvious because the walls of the container become harder to move, because there are more molecules of gas in the headspace colliding against the container's walls. I don't see what more evidence you need. Given time, equilibrium will become reestablished and the container will return to the original hardness.

It is not obvious to me because I do not feel the walls of a soda bottle get firmer when I shake. What makes you think the CO2 molecules are coming out of solution faster than they are reentering? What would convince me is to measure pressure at stasis, shake and measure again.

 

[Hex23]

This is an excellent effort. Did you ever explain where the temp probe was? I still think that the spike may be influenced by temperature or some other anomaly. I was searching for the thread that showed anoldUR's similar experiment and he didn't get the spike. It would be nice to figure out they the results vary.

Thank you.

You've probably sensed that I'm not ready to draw any conclusions just yet.

For one, the shape of the decay doesn't look like what I might expect. I suppose to really rule out leaking, I'd have to run a big study to establish how likely it is to leak (gasket placement, screw torque, etc) or get a CO2 detector. Neither of those is going to happen
Based on the results of the leak test I'm fairly confident in the capability to avoid leaks.

The temperature measurements came from an RTD with very small thermal mass (Auber Instruments) which was tucked behind that spounge you see in the picture. I decided against a true thermowell because of how complicated (with my skills anyway) it would have been to construct.

While I was getting ready to run the experiment, I thought about the physics behind the problem and I was convinced that the "rise to a peak, then fall" phenomena could happen, given one assumption. If the yeast generated CO2 faster than the surrounding liquid could absorb it, given the current equilibrium conditions), then it would evolve (not bubble) off and pressurize the headspace, then go back to equilibrium. But honestly I didn't study the absorption/evolution rate vs yeast CO2 production rate rate enough to know whether this was possible.

Absorption is a pretty slow process (as seen by common kegging practice) and evolution is a relatively fast process (as seen by the small amount of time it takes a beer/pop to go flat).

Your point about the other graphs people have drawn is a good one, which I had considered before I ran the experiment the third time. Up until 1/26, I just figured that my experiment was saying the same thing as theirs. But once the pressure started going down the question opened back up.

 

[Bobby_M]

Well, I love a good mystery so thanks for that.

 

[dbsmith]

It is not obvious to me because I do not feel the walls of a soda bottle get firmer when I shake. What makes you think the CO2 molecules are coming out of solution faster than they are reentering? What would convince me is to measure pressure at stasis, shake and measure again.

I went to the store today and bought a soda bottle, just to be sure about this. Cracked it open and closed it back up tightly. The bottle was very easy to squeeze. I shook it up and now it is incredibly firm. The only explanation is that shaking caused gas to come out of solution. I don't think that there is any other explanation as to why the container is firm.

 

[passedpawn]

I went to the store today and bought a soda bottle, just to be sure about this. Cracked it open and closed it back up tightly. The bottle was very easy to squeeze. I shook it up and now it is incredibly firm. The only explanation is that shaking caused gas to come out of solution. I don't think that there is any other explanation as to why the container is firm.

Did it get warmer?

 

[passedpawn]

I could do this test really quickly buy just filling my bottle w/gauge (see post #1 ), capping, shaking, and watching the needle.

 

[dbsmith]

Did it get warmer?

On a molecular level, molecules are colliding with each other and transferring kinetic energy to each other. Some have higher amounts than others. The heat is proportional to the average of the kinetic energy of all of the molecules in the solution. So the shaking may have increased the overall kinetic energy, but I doubt that a typical thermometer would show any difference in temperature. But who knows? Maybe it would..sounds like another experiment

 

[dbsmith]

I could do this test really quickly buy just filling my bottle w/gauge (see post #1 ), capping, shaking, and watching the needle.

Please do, as your cool device using numbers would probably be more convincing than my 'container feels much harder' evidence.

 

[passedpawn]

Please do, as your cool device using numbers would probably be more convincing than my 'container feels much harder' evidence.

Alright, I'll get some video too. Stay tuned...

 

[passedpawn]

Damn, had to fix a leak. Now I've got to drink the beer before I can attempt the test again. Might have to wait till tomorrow.

 

[shelly_belly]

I went to the store today and bought a soda bottle, just to be sure about this. Cracked it open and closed it back up tightly. The bottle was very easy to squeeze. I shook it up and now it is incredibly firm. The only explanation is that shaking caused gas to come out of solution. I don't think that there is any other explanation as to why the container is firm.

When you opened the cap you released the pressure in the headspace and altered the system. To restore equilibrium some of the CO2 would have to migrate from the solution to replace the loss of pressure in the headspace. This would be accelerated by shaking.

 

[dbsmith]

When you opened the cap you released the pressure in the headspace and altered the system. To restore equilibrium some of the CO2 would have to migrate from the solution to replace the loss of pressure in the headspace. This would be accelerated by shaking.

Right, this is exactly what I was trying to prove. Equilibration takes time, and that shaking can induce gas to come out of solution. You know, crap, I should have left the bottle alone after shaking it to see if CO2 would be reabsorbed and the container would go back to being less firm. But, I drank it Though, I think we all know what happens when you shake someones can/bottle of soda. You have to let sit for several minutes so that equilibrium can be reestablished.

 

[passedpawn]

I should have left the bottle alone after shaking it to see if CO2 would be reabsorbed and the container would go back to how it was before shaking. But, I drank it

Great scientific method. Eat the experiment before all the data is collected.

 

[dbsmith]

You know after thinking about it, the little soda bottle experiment did prove that you can shake gas out of solution, but it didn't answer the question if shaking will bring it out of solution for a system that is already in stasis...The reason I cracked it open was because upon purchasing the bottle was ridiculously hard already and I wouldn't be able to tell if there was a difference just by feeling it. One of you guys with the pressure gauges, maybe you should let a filled bottle of soda sit until the pressure gauge doesn't change anymore, and then shake the bottle and see if there is a change.

 

[dbsmith]

Great scientific method. Eat the experiment before all the data is collected.

Haha, that's how I roll.

 

[surferjoe]

No carbonated beverage increases in pressure when shaken, not even Champagne, but the increase of nucleation sites allows the gas to rush out more quickly and with more liquid in foamy tow: http://www.phys.csuchico.edu/kagan/professional/papers/soda.pdf, http://tinyurl.com/serwayjewett
After opening the container, closing and shaking it helps the bottle reach a new equilibrium.

Yeast farts on the molecular level, producing 2CO2 at a time, each about 0.3 nanometers long. As they are produced throughout the beer they are absorbed into it, and the headspace, in equilibrium. CO2 absorption is very slow as it occurs through diffusion (http://en.wikipedia.org/wiki/File:Chemical_surface_diffusion_slow.gif). The data in this thread suggests that at peak fermentation CO2 could form faster than the beer can absorb it, disrupting equilibrium and collecting in the headspace. I can't find studies on CO2 formation vs absorption in beer, but it would definitely vary with yeast strain, alcohol %, and temperature.

 

[dbsmith]

No carbonated beverage increases in pressure when shaken, not even Champagne, but the increase of nucleation sites allows the gas to rush out more quickly and with more liquid in foamy tow: http://www.phys.csuchico.edu/kagan/professional/papers/soda.pdf, http://tinyurl.com/serwayjewett
After opening the container, closing and shaking it helps the bottle reach a new equilibrium.

Yeast farts on the molecular level, producing 2CO2 at a time, each about 0.3 nanometers long. As they are produced throughout the beer they are absorbed into it, and the headspace, in equilibrium. CO2 absorption is very slow as it occurs through diffusion (http://en.wikipedia.org/wiki/File:Chemical_surface_diffusion_slow.gif). The data in this thread suggests that at peak fermentation CO2 could form faster than the beer can absorb it, disrupting equilibrium and collecting in the headspace. I can't find studies on CO2 formation vs absorption in beer, but it would definitely vary with yeast strain, alcohol %, and temperature.

Well damn. It looks like I was wrong about the shaking of a liquid in equilibrium bringing out gas. I'd still like to see one of you guys with a pressure gauge cap shake a carbonated liquid in equilibrium just for fun though to validate it

The data does however seem to show that the headspace can have more CO2 than it would normally have at equilibrium while it is carbing up though.

If yeast are producing CO2 and releasing it one molecule at a time, it seems that it would be dissolved pretty easily, and that for any gas to build up into the headspace, it would first have to 'un-dissolve'. If this were true, then there would never be more gas in the headspace...but the data shows otherwise.

It makes me curious about the underlying assumption. While CO2 is made in quantified amounts during metabolism, is it actually released from the cell the same way? I know gas can diffuse through a cell membrane freely, but does that imply that it is one CO2 molecule at a time? A quick google search didn't turn up anything for the mechanism of CO2 exiting a yeast cell.

 

[Brewbuzzard]

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.

The Germans have used this method for years to know when their Hefe Weizen is finished bottle conditioning.