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Cold crashing fast or slow

Should I drop the temp gradually down or drop it quickly? Do I need to worry about my airlock freezing? Should I replace star san solution with vodka? Getting ready to cold condition my Kolsch. Cold condition is the correct term since its an ale correct?

If fermentation is complete, go ahead and drop the temps right away. Remove the airlock and replace with a solid stopper or foil as it will suck air in.
It’s cold crashing whether it be an ale or lager. Lager is cold storage which to me is at least a month.

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I’ve had good luck with using an S type airlock using vodka. I ferment in a chest freezer with a dual stage temp controller. I just drop the temp down to the low to mid 30’s for a couple days. Also, some are concerned with using an S type for this because of the outside air passing through the airlock. With vodka you should never have a problem and also assuming your Carboy is inside of a unit similar to a fridge or freezer, there’s no real outside air to worry about anyways because the unit is sealed.

Not saying that blocking it off completely is bad, but I personally get nervous watching my plastic big mouth bubbler cave inward. S type airlocks will prevent this from happening.

But now that we’re on this topic, I’ll ask this to loopie_beer… Do you think that an Stype airlock would possibly allow oxygen into the carboy and more than likely oxygenate the beer?

I certainly didn’t seal it tightly. I folded some foil over the opening and made sure it lightly slide up and down with some room under lip of the neck. I’m not worried about an infection at this stage. I’m sure there is a small blanket of C02 over the beer since its heavier than air.

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As @mhall2013 said, there’s a blanket of CO2 over the beer which will help prevent O2 uptake. In addition, the beer will actually start reabsorbing any CO2 in the headspace further preventing O2 uptake.

Without even using a spundling valve, I’ve had lagers come out almost carbed because of the cooler ferment temps, less violent fermentation, and cold crashing/lagering.

I’ve never cold crashed before and normally use the current beer temp in the priming sugar calculator. So with the beer this cold it will hold more C02 in suspension so it should adjust for it in the calculator? Do you let temp rise before bottling?

Use the warmest temperature the beer rested at after the fermentation ended. The end of fermentation means no additional CO2 was produced and CO2 in solution would begin off gassing. You can bottle the beer cold immediately after the cold crash or let it warm to room temperature.

I don’t know much about brewing beer, but the idea that CO2 will form a protective layer over the beer while the air (20% Oxygen) will float above the CO2 really doesn’t work. Gasses mix even if left undisturbed. If gasses didn’t mix, those of us living at sea level would suffocate in a layer of CO2, folks at higher elevations would be subject to sudden, catastrophic fires due to a pure O2 atmosphere, and higher still everyone would suffocate on nitrogen.

A sealed fermentation chamber or CO2 flushing is the only way I’m aware of to keep oxygen away from the beer.

All that raises the question: How did our ancestors make good beer? Maybe it doesn’t matter much at all.

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I’m not doubting you @old_dawg… But this makes sense as to why some people at sea level aren’t as bright and those in the mountains seem to have their heads in the clouds!

All joking aside I assume you are correct as I think I read another post of yours in regards to gases. I know you know more about them than I!

I do disagree though in that it doesn’t provide any protection. There’s a lot of other factors that could cause CO2 and O2 to mix in the environment (say wind for example) that may not be present in a fermenter. As I said, I’m not saying the 2 gases don’t mix but maybe not as much (??).

And I would also agree with you that it’s probably not as big of a deal as one would think. They’ve made beers for years. Sure they may have improved over what was once made but look even at sanitization; although important it’s not something to worry sick about.

I had a lid off the other day on a beer that wasn’t completely fermented. Took a sniff. Oops there may have been some O2 not enough to sustain life though. I believe it would take a little time to diffuse enough in to damage the beer. The little pulled in from cold crashing probably isn’t enough to make a difference IMO.

I agree with Loopie and Cat. If the headspace is full of CO2, the little bit of air that gets mixed in when some air enters through the airlock or even from opening the fermenter will contain so little oxygen that it gets diluted to insignificance.

If I didn’t live at 35 feet above sea level, I’d probably have thought of that!


You can’t compare the Earth to a fementer with respect to fluid dynamics. Gasses will settle into layers in a fermenter with the CO2 settling on top of the beer, displacing the other gases because of the fact that there is no atmospheric action to mix the gasses. On earth we do not have this issue because we have dynamics that cause movement of air. The atmosphere is always in motion on earth, while in a sealed fermenter there is nothing to cause mixing. It’s just like putting vinegar and oil into a salad dressing container. Left alone to sit still it will separate into layers, while if you were to add energy in the form of motion it would mix into a homogeneous liquid. On Earth, we receive energy from the sun, and that causes wind. Wind mixes the gasses. In a fermenter at a fixed temperature in a refrigerator that will not happen, and just like the vinegar and oil, the gasses will settle into layers.


But when you cold crash you drop the temp causing air to suck in (wind) and mix with the co2 correct? Also when taking off the lid your creating movment. I still think its not enought to worry about but i feel like if your opening up your fermentors too much for sampling ect… then you may cause some oxidation.

I’m going with In The Basement’s theory, also I ferment in the keg now… there will be no turbulence, well except when cooling…. I’m going to have to ponder that… Sneezles61

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