Physics Question

[yankeessuck888]

I have beer fermenting, with a blow-hose out of the top of the carboy, submerged in a cup of vodka. I know this happens fairly frequently, but I'm curious as to why - why does some of the vodka get sucked INTO the carboy? Something is providing enough suction to get some the sweet, sweet vodka all the way to the apex of the tube, starting a brief siphon. What is it?

 

[DuckAssassin]

A decrease in temperature inside of your carboy would cause the pressure inside of the carboy to drop. Since there is then more pressure on the vodka on the outside of the blowoff tube than the insde, the vodka rises up. I can't imagine enough of a temp change to suck vodka all of the way into your beer, unless the highest point of the blowoff tube is only slightly higher then your vodka. There would be additional reasons if you are using a plastic carboy (better bottle).

 

[uwjester]

It happens to me when I try to move the bucket for one reason or another, usually in the first day or two so I can see the thermometer. I apply pressure to the sides of the bucket, pushing the CO2 out the airlock. When I remove pressure, sweet sweet vodka gets pulled into the bucket.

 

[VTBrewer]

Does it happen once fermentation is going? If so i don't know. If not, what was the temp when you put in primary? If the air in the headspace cools...and contracts...it would suck up a little i suppose.

 

[Parker36]

Changing temperature or the beer (cooling of the beer can cause it to draw in from the blow off hose) or an increase in ambient atmospheric pressure can both cause this. Also, not exactly passive, but if you push down on the lid of a bucket, then allow it to reform to original shape, it will draw in.

 

[notwoohoo]

I'd suggest a big bore blowoff tube is you are using a carboy. There won't be any problem with 1" ID tubing (1.25" OD)

 

[NewBrew75]

Good question, heck if I know.

Maybe this will help:

E=mc^2
Acceleration rate of gravity: 9.8m/s/s
Relativistic momentum: p=ymv

 

[r2eng]

Actually, PV=nRT, where

P=pressure
V=volume
T=temp

To achieve equilibrium, as T decreases, either the pressure or volume needs to decrease. As stated above, it's most likely temperature. The temperature will drop a bit as fermentation ceases.

 

[Fingers]

The beer is sucking in air. Think of it like the beer is taking a big, deep breath. After you drink the beer, it exhales. Some of the exhale comes out of your mouth and some comes out the other end. The stuff that comes out the other end is heavier because it has more of the bad, smelly beer stuff in it. That's why beer burps don't stink.

 

[notwoohoo]

The beer is sucking in air. Think of it like the beer is taking a big, deep breath. After you drink the beer, it exhales. Some of the exhale comes out of your mouth and some comes out the other end. The stuff that comes out the other end is heavier because it has more of the bad, smelly beer stuff in it. That's why beer burps don't stink.

I don't know whether to take this seriously or not :cross:

 

[Kungpaodog]

The beer is sucking in air. Think of it like the beer is taking a big, deep breath. After you drink the beer, it exhales. Some of the exhale comes out of your mouth and some comes out the other end. The stuff that comes out the other end is heavier because it has more of the bad, smelly beer stuff in it. That's why beer burps don't stink.

You should take this very seriously. Because if you were to stand on your head after drinking a beer, all kinds of awful things could happen.:cross:

 

[Fingers]

You should take this very seriously. Because if you were to stand on your head after drinking a beer, all kinds of awful things could happen.:cross:

Especially if you were two girls drinking out of the same cup!

 

[yankeessuck888]

Good answers, thanks guys. It wouldn't be a post about physics if it didn't end with a mention of 2 girls 1 cup.

 

[ColoradoXJ13]

Actually, PV=nRT, where

P=pressure
V=volume
T=temp

To achieve equilibrium, as T decreases, either the pressure or volume needs to decrease. As stated above, it's most likely temperature. The temperature will drop a bit as fermentation ceases.

I was gonna respond with

"PV=nRT *******!"

but mostly I just want to have my avatar in a thread by an ignorant Sox fan

 

[EoinMag]

When I'm moving my beers, I tend to bend the blow off tube in two, then tape the kink with electrical tape so nothing is going through there either direction. I then move the fermentor and remove the tape straighten the kink out of the elbow I've made then pop it back in the jar with the sanitiser in it. I'd not use sweet sweet vodka in those quantities myself in the blow off, I tend to only use sweet sweet vodka in the bubblers. In fact this time I committed pretty much a crime and put grasowska in there as it was the only sweet sweet vodka that I had at the time, but it's ok I got it cheap from Germany.

 

[uglygoat]

You should take this very seriously. Because if you were to stand on your head after drinking a beer, all kinds of awful things could happen.:cross:

reminds me of the south park episode where cartman proves you can reverse the direction of the digestive system.

 

[Mr. Nice Guy]

Yeah don't believe that guy, the beer sucks in vodka because it is thirsty, I mean come on...