Adding CO2 To Secondary

My glass secondary's are 2 or 3 litres to big and therefore I can never get them full. If I were to attach a piece of plastic tubing onto the "in" side of my corny keg using a tie strap and then run the tubing into my secondary and then give it a shot of CO2......would that work to create a protective layer and therefore put me in the same position as if my secondary were full with no airspace?
If this makes sense would it be better to run the gas into the liquid or into the air on top or would it make no difference?
Thanks for any positive input.

I do that all the time. You don't want to bubble it through the beer. Just gently place some in the head space to displace the oxygen.

Is it needed? I was told before that the headspace in the secondary is fine, some continued fermentation will naturally expell the oxygen and the contact patch is minimal. Have I been instructed incorrectly?

I often purge head space in secondaries with CO2 directly from the CO2 tank. During secondary/conditioning not much yeast activity is taking place so not much CO2 produced.

I do this particularly with meads as they age since we may consume some samples along the way...thus introducing air and potentially contamination.

I set my regulator to a low pressure (less than 10psi). Remove the gas quick disconnect from the end of the low pressure hose. Insert into the secondary, open valve, and let it flow until I think enough volume has flowed.

I also find this will kill off potential infections on the surface. Many of the bacterial strains which grow on the surface need some O2. I've purged secondaries which showed some growth and cleared it right up.

Fermentation should not be occuring in the secondary. After the first 7-10 days in the primary, your beer has pretty much completed fermentation. You typically want to avoid headspace in the secondary at all costs. But that is not to say that some headspace in the secondary (without flooding it with C02) will ALWAYS ruin your beer. It depends on how much headspace you're talking about, if that space is being taken up by a bunch of leaf dryhops, how carefully you racked, etc. To limit oxygenation, I would recommend that you only rack to secondary when needed. And if you do, be sure to fill it up with as much beer as you can, leaving as little headspace possible.

Thanks for the replies. This was easier to do then I would have thought and no tie strap needed. Wasn't sure how long to let gas run. Hoping 30 sec was long enough to put a layer over the beer.

MustGoFast said:

Is it needed? I was told before that the headspace in the secondary is fine, some continued fermentation will naturally expell the oxygen and the contact patch is minimal. Have I been instructed incorrectly?

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Wouldn't say it is necessary. But, it can only help. For me, it seems to help my hoppy beers stay fresh longer. Course......it very well could be just in my head.