Cold crash suck-back volume estimate?

[Vale71]

The keyword here is dissolved oxygen, as in it's already there and will instantly mix with the beer. Atmospheric oxygen takes time to dissolve and in any case the discussion here is about ways to effectively prevent oxygen ingress in the first place, particularly vis-a-vis the barbaric practice of cold-crashing. Saying "but air contains oxygen anyway so why bother?" really makes little sense in this context...
So you're saying you actually dump boiling water in your fermented beer? Must make for a very nice foam display.

 

[d40dave]

I wouldn't say it's boiling but still pretty hot. Probably about as hot as when I dump 2 cups of water with priming sugar in my bottling bucket. What foam display are you referring to?

 

[Vale71]

If you pour boiling water in even partially carbonated beer CO2 will be released and with no headspace to speak of that foam is bound to overflow. I'm guessing your water is much colder than that and therefore has a significant amount of dissolved O2, not counting what your beer has already picked up during transfer, making your process quite ineffective as far as preventing oxygen ingress is concerned compared to the alternative discussed here, i.e. no transfer with suck-back prevention.

 

[d40dave]

I thought you said it takes time for atmospheric oxygen to dissolve. I realize some people do not like secondaries for various reasons. But if one is used the problem of suck-back becomes less of an issue if the secondary has little headspace.

 

[The_Bishop]

You will still have suck-back, as the negative pressure is caused by the colder liquid absorbing more gasses, not just CO2. You also have the volume of the liquid itself shrinking due to the temperature change.

 

[d40dave]

You will still have suck-back, as the negative pressure is caused by the colder liquid absorbing more gasses, not just CO2. You also have the volume of the liquid itself shrinking due to the temperature change.

I would think that since I have less than 10 square inches exposed to gas versus 250 square inches that the rate of absorption will would be proportional but certainly less. But that is just speculation. Anyway, it's finally getting warmer around here so I'm done with cold crashing until next Winter.

I agree that all the little things add up. It's a learning process. Time, expense and other factors make for determining what's best in ones situation.