Is alcohol stratification possible?

[Dland]

I was wondering if alcohol stratification is possible in keg. In this case, there probably is some temperature stratification as well. (am experimenting with new and imperfect external cooling coil while spunding lager).

I got the same gravity reading 5 days after racking from primary as the day I racked(1.018).
The kegs are clearly working, have spunded up past 30PSI and I have let off some CO2.

It is same hydrometer, and have of course read samples at same temperature. Stratification is the one explanation that comes to mind.

To broaden the question, have also wondered if alcohol can stratify after long lagering, even at uniform keg temps. Sometimes it seems to, but may be subjective observation.

 

[Oginme]

Ethanol is completely miscible in water since both are very polar molecules with complementary charges. Ethanol and water bond together so well that they form an azeotrope, a combination which lowers the boiling point of the water/ethanol bonded molecules, which is why it is difficult to attain pure ethanol through straight distillation of the mixture.

 

[yoop89]

If your spunding did you degas your second sample prior to reading? Depending on how much CO2 has dissolved it could throw off your reading. Even when pulling samples from my fermenter I try to make it standard practice to swirl with a long toothpick to try and knock out as much of the CO2 as possible.

 

[Dland]

I usually let my hygrometer samples sit over night and they get a swirl, so I doubt CO2 is holding it up.

Back to the stratification however, if the top of keg is several degrees warmer than bottom of keg due to the cooling coils having slipped down, wondering if the wort at top could work faster than the wort at bottom, and be higher ABV. Would the brew necessarily mix itself in keg?

I understand once it is mixed, the molecular bonding makes separation of alcohol unlikely.

 

[Vale71]

I think the simplest explanation, i.e. a stalled fermentation, is the first thing you should be looking at.
Temperature stratification is possible but very hard to achieve in such small vessels.
Out of curiosity, how do you measure the beer temperature inside a sealed keg?

 

[Dland]

^^^Fermentation not stalled, PSI measured twice daily and vented when gets over 30.

Inkbird 308 temp probes(3 at different levels) attached tight to keg then insulated.

Edit: Add the observation that there is about 2 degrees F between top and bottom temp probes. Since thermal conductivity of keg wall is likely greater than the brew, is an interesting but imperfect data point.

 

[Vale71]

I won't go as far as to say that your measurements are completely unreliable, but without an internal probe you're not really measuring the temperature of the wort and so it's anybody's guess what temperature it's really at.
As for venting, it takes very little sugar to create a large volume of CO2, so unless you're measuring how much CO2 you're actually venting fermentation could very well be proceeding at a really slow pace, as shown by gravity measurements.
Anyway, since it's a small vessel you could just check if there is a stratification issue by shaking it vigorously a few times and then taking a new measurement.

 

[Dland]

10 PSI vented every 12 hours is working yeast, esp at low controlled temps. Not new to spunding.

I realize I can shake the kegs, I asked original question out of curiosity.

 

[Vale71]

10 PSI is not a measure of quantity but of pressure. If your headspace is very small you're not venting much CO2 and as I said it doesn't take much fermentable sugar to create a small amount of CO2 so fermentation might very well be progressing at a much slower pace than you can detect with your measurements.
Anyway, sorry I took your question to heart and tried to give you some more advice, I promise it won't happen again.