where does the CO2 go if you use a vacuum?

[BernardSmith]

A naive question perhaps: I am using a Mityvac (automotive) vacuum to degas my wine. I can create a vacuum of about 20 inches. I am unable to maintain this vacuum for more than a few seconds. Is the loss of the vacuum what prevents the CO2 from being re-absorbed into the wine? If you are able to create and maintain a good vacuum for say 20 minutes, where would the CO2 that is released from the wine go? It cannot escape the carboy. Why isn't it reabsorbed into the wine? Should I be trying to find a way to maintain the vacuum for a significant amount of time or should I be thankful that I need to keep on pumping to create the the vacuum

 

[rjb222]

The vacuum is created only because there is nothing being pumped out. The 20 inches pf vacuum you create pumps out while you are pumping the handles. When there is no more co2 coming out to fill the void you get your 20 inches of vacuum. So basically you pump the co2 out.

 

[vacuumpumpman]

If I understand this question correctly – when you apply vacuum to your carboy and co2 is realized the vacuum goes down- that is normal as the co2 is being separated from the wine (liquid). At times when you vacuum rack you will notice that even a vacuum pump will sometime have a hard time keeping the vacuum up – due to all the co2 being realized.

 

[BernardSmith]

I think I understand: the carboy plus vacuum pump is not a relatively sealed unit but a unit that is continuously pumping out gases (CO2 etc) to the environment outside and beyond the carboy. I guess I kind of assumed that the carboy and pump were a sealed unit (much like the way a bicycle pump pumps air into a tire - except in reverse) and that the continual drop in vacuum was because of imperfections in the bung or pump (to use the analogy of the bicycle pump - any air escaping from from the tire as I pump would be because of either damage to the tire or to the air pump).

 

[DoctorCAD]

It IS exactly like a bicycle pump only in reverse.

Where do you think the air that gets compresses into the bicycle tire comes from?

It is pulled into the pump body when you pull the handle up and then pressed into the tire when you push down on the handle. The vacuum pump does exactly the same thing, but in reverse. As you lift up on the pump handle (or squeeze it in) the pump sucks air plus any CO2 out of the carboy, and when you push down (or let go of) the pump handle it expels that air into the surrounding air. The vacuum pump does have a check valve built in to keep the vacuum in the carboy.

The CO2 coming out of suspension is what causes the vacuum in the carboy to deplete, and that is what you want!

 

[BernardSmith]

Aha.. Thank you all. Now it is clear. I actually feel much better about using the Mityvac than I did yesterday! I was concerned that a great deal of the CO2 was simply being re-absorbed into the wine and so like Sisyphus who was condemned to spend eternity rolling a rock up hill only to have the rock roll back down to the foot of the hill when it reached the top, I imagined that I would be degassing from now until hell froze over if the CO2 was being re-absorbed back into the wine. But it is now clear that the system is quite "open" and all the gases in the carboy are being expelled into the room .. but like I wrote at the beginning I was aware that my question might be very naive. Thanks for your patience and your explanations.

 

[rslayback]

Does that mean if a wine saver is used to degas, an individual must release the pressure to get rid of the C02?

 

[vacuumpumpman]

I am assuming you are referring to vacuum when you mentioned pressure - correct ?
That answer would be no - creating a vacuum or a negative pressure will pull out the CO2 and cause the vacuum to stabilize after awhile. Lets say it takes 20'' of vacuum to remove CO2 - and 15'' of vacuum it will not remove CO2. Once the CO2 is released from your wine the vacuum will also causing no more removal of CO2.
That is why alot of people went with a vacuum pump over a wine saver due to time and hand strength, and a vacuum pump will definitely remove more CO2 also.