Too much headspace in secondary

[philosofool]

I racked a czech amber lager to secondary about 15 minutes ago and then realized there's way too much headspace. I only got about 4.5 gallons, so there's over half a gallon of space in the carboy. That's going to oxidize the beer during lagering, which I obviously don't want.

My options:
(1) top off with distilled water. The beer is pretty strong with a highish finishing gravity (1.060 OG, 1.017FG) so it will still be an ample beer even if diluted.
(2) top with some wort made form DME
(3) ferment some DME wort and transfer it into the beer.

(3) would be very quick, since I still have the yeast cake from the beer in the fermenter. I sthere any reason to prefer 1 or 2? My concern with 2 is that I could generate some off-flavors since most of the yeast was left behind at racking and that it will take along time.



I

 

[Boomer]

Do you keg?

 

[philosofool]

Yes, I keg. I think I see where this is going.

 

[Boomer]

I’d just purge the secondary with CO2 and carry on.

 

[gunhaus]

Why not just transfer it to a keg, purge the headspace and lager in that?

 

[RM-MN]

Top is off with some DME in water and you have a true secondary fermentation. That will cause the yeast to ferment some more and they will scrub the oxygen from the remaining headspace and replace it with the CO2 that you lost when you transferred to secondary. The CO2 on top of the beer helps protect it from infections as most bacteria cannot reproduce in a CO2 atmosphere.

 

[Yooper]

Keg it, purge with co2 before and after filling, and lager it.

You don't want to add anything to the beer, especially water, and purging is at best temporary in a carboy. A keg is the perfect lagering vessel.