Headspace?

[Rice_Guy]

Time is the big variable in this, I would have no issue on a week, the head is more than I like and another trick might be to float synthetic corks filling the void. ,,, however it was rather easy to bottle and stop the issue.

 

[David Violante]

There is no such thing as a blanket of any gas. You can use the nitrogen to purge the headspace, that is, expel the O2-containing air out of the headspace. Then you put an airlock on it. (At this point, the diffusion of O2 through your airlock is the relevant rate to consider, but experience seems to indicate that this diffusion is not enough to ruin your wine.)

As far as N2 diffusing into your wine, this is not a concern. First of all, air is ~3/4 N2. Second, N2 is inert.

Thank you, that makes a lot of sense~ I’ve been using nitrogen for about a year now and had always thought it created a bit of a blanket when settled since it was heavier than other gasses. Of course I suppose now thinking about it there would have to be a lot of other gasses in there too. Not sure where I read all that. I appreciate your experience, thank you again~ this is definitely such a great place to learn.

 

[sour_grapes]

Thank you, that makes a lot of sense~ I’ve been using nitrogen for about a year now and had always thought it created a bit of a blanket when settled since it was heavier than other gasses. Of course I suppose now thinking about it there would have to be a lot of other gasses in there too. Not sure where I read all that. I appreciate your experience, thank you again~ this is definitely such a great place to learn.

I understand that you got the point, and not to beat a dead horse, but N2 is the LIGHTEST of the gases under consideration, not the heaviest. Not by much, and it does not matter one whit anyway. Gases don't "settle." Their thermal motion keeps them completely mixed (to about 1 part in 10,000) regardless of their weight.

 

[David Violante]

I think this is fantastic information... and very much appreciated.

I was under a mis-conception of how this all works. I love the science behind things and so looked it up to better understand. Oxygen has an individual molecular mass of 15.99 g/mol and since it is diatomic the total mass (weight) of [O2] is 32 g/mol (rounded). Nitrogen behaves similarly and is at 28 g/mol, and Carbon Dioxide comes in at 44 g/mol. [Illinois University Department of Chemistry, 2020; Engineering ToolBox, (2009). Molecular Weight - Common Substances.]

I can see very clearly now that by adding Nitrogen to the headspace, it is displacing other gasses and not creating a cozy blanket under which no oxygen would float (at that specific moment and until other gasses are potentially introduced by either CO2 coming out of solution / being created by active yeast, or anything coming in from a poor airlock).

Thank you again... this changes my outlook and practice by really knowing what's going on. Fascinating...

 

[Bill Pet]

I've mentioned this before in another area. I use a harbor freight brake hand vacuum pump to pump a 20 inch vacuum for degassing. Once it is degassed I continue to leave the carboy with a 15 to 20 inch vacuum. I'm pretty sure that the partial 02 pressure at that vacuum will prevent any further 02 from entering the wine and so don't worry about headspace. Am I wrong?

 

[sour_grapes]

I've mentioned this before in another area. I use a harbor freight brake hand vacuum pump to pump a 20 inch vacuum for degassing. Once it is degassed I continue to leave the carboy with a 15 to 20 inch vacuum. I'm pretty sure that the partial 02 pressure at that vacuum will prevent any further 02 from entering the wine and so don't worry about headspace. Am I wrong?

I think you are on a good track, but I don't fully understand your description, and you may be a bit off-base.

I don't know what you mean by the reduced partial pressure "will prevent any further O2 from entering the wine." Any O2 left in the headspace has complete access to your wine.

If you pump to 20 inHg, you remove about 2/3 of the air. (I am assuming you don't live at high altitudes.) Naively speaking, you could assume that you have removed about 2/3 of the oxygen. So, if you had 3 liters of headspace, then your pumped headspace would (naively speaking) leave the chemical equivalent of about 1 liter of headspace at atmospheric pressure. Personally, that is not an amount that I would be comfortable with, but it is your wine.

I keep saying "naively," because I think your situation will be more favorable than the one I cite. I suspect that when you pump on your headspace, you are causing CO2 to evolve from the wine. That probably means that your remaining atmosphere after pumping is more dilute in O2 than air is. So, in the situation described above, you might have the chemical equivalent of, say, 1/2 liter of headspace. (I am totally making up that last figure as an example.) But any O2 that is left in the headspace is fully free to chemically react with (oxidize) your wine.

 

[Rice_Guy]

Paul, he should have pretty good dilution if he pulls the vacuum, waits 12 hours and pulls the vacuum a second time, waits 12 hours and repeats a third time.

One of the wineries up north has a nitrogen cylinder on their racking tanks and just keeps half a pound over pressure in the system as a slow flush.