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Hex23 10-25-2012 04:59 AM

1 Attachment(s)

Here is the data from this batch. One procedural differences to highlight ... This time I switched to a wider bottling wand which left more headspace than last time (probably double the headspace as last time, about 2"). I'll probably go back to the narrower bottling wand b/c I don't like that much headspace.

Now some comments on the data. Near the beginning there is about 12 hours of missing data where the monitor crapped out. Think I know what happened and how to avoid it next time.

The initial pressure rise was really fast.

I don't really know why, but the pressures never really reached where I would have expected. I doubt it can be attributed to the increased head space. If the data is right then the CO2 in this bottle is about 1.5 volumes. I'll say that other bottles from this batch are properly carb'ed - definitely more than 1.5 volumes. I haven't cracked the monitoring bottle yet.

I do see some similar artifacts as last time (besides the 24 hour cycle) - looks like overshoot, then oscillations settling to a mean.

I'll also mention that today we did not have the AC on and local outdoor temps reached 80. That's the probable reason for the last spike.

Any thoughts on what I should do differently next time? I may have to put the bottle in my fermentation chamber to keep the temp more constant. This water bath was not a temp controlled bath - just more thermal mass to try to slow the swings and apparently wasn't very effective. I'll also see if I can get a temp recording. Would be cool to have a gravity reading too, but I can't imagine how to do that.


Hex23 10-31-2012 04:21 AM

1 Attachment(s)
Quote:
Originally Posted by Hex23 View Post
I did go on weather underground to get external temps for my area from that timeframe, but my recollection is that when I graphed them together with pressure there wasn't any obvious correlation. However, I agree that other phenomena (drafts, etc) could have contributed. Ultimately I need to measure ambient temps - and maybe do a better job controlling them.
I guess I'm not really sure what I did back then ... but, I went back and graphed average outdoor temps vs pressure and there does appear to be some correlation. I still want to run the experiment with more temp control and recording just to see if this is all due to temps. I also filtered out the signal with 24 hr period in this data.

dbsmith 11-14-2012 02:40 AM

1 Attachment(s)
Quote:
Originally Posted by Bobby_M View Post
Disagree. A bottle of sealed soda has co2 at equilibrium. Shaking does not pull co2 out of solution because it can't. The partial pressure in the headspace and the newly formed bubbles already matches that of the dissolved co2. The reason it gushes after shaking is that the bubbles create nucleation point similar to mentos in diet coke.
Shaking can pull it out of solution because nucleation (from energy input spent shaking) IS causing CO2 to escape from the liquid (evidenced by the bottle hardening) and it is not being replaced back into solution at the same rate, and therefore it is no longer in a state of equilibrium. Equilibrium doesn't imply that two things are equal, it just means that reactions going both directions are happening at the same rate. After shaking the bottle and causing CO2 to escape from solution, there is excess CO2 in the headspace above the liquid due to the energy put into shaking the bottle, and according to Le Chatelier's Principle, after the shaking has stopped (no more energy input on reactant's side), excess products on one side will cause the reaction to shift so that more reactants are created. Basically, CO2 will begin dissolving faster than it is escaping the liquid. But it still takes time for equilibrium to be established again. CO2 is CONSTANTLY seeping out of the liquid and being absorbed. In equilibrium, these rates are the same. When you put in energy (such as shaking), you are disrupting the equilibrium. This principle also explains the effect of temperature, because the K value changes with it.

EDIT: here's a picture

Hex23 01-31-2013 04:05 AM

4 Attachment(s)

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:

Attachment 97711

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

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.

Attachment 97708

Attachment 97709


Hex23 01-31-2013 04:05 AM

4 Attachment(s)

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:

Attachment 97711

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

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.

Attachment 97708

Attachment 97709


Hex23 01-31-2013 04:05 AM

4 Attachment(s)

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:

Attachment 97711

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

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.

Attachment 97708

Attachment 97709


Hex23 01-31-2013 04:05 AM

4 Attachment(s)

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:

Attachment 97711

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

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.

Attachment 97708

Attachment 97709



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