Next Question 19L Recipes in 25L Carboy

First thanks for being patient and answering all my questions. It's been immensely helpful.

My question is, I’m thinking about getting some pre-made extract kits from Alternative Beverage and I’m guessing they’re for 5 US Gal. (19 Litres). Also most recipes on the net are for 5 US Gal. I’ve got two 5 Imp. Gal (23 Litre) Glass Carboys (that I use as secondary’s) . My LBS guy said I had to make sure the liquid was up to a couple of inches of the neck of the Carboy. But I’ve seen lots of pictures here where there is lots of room in the Carboy. Some only half full. Is it important to leave as little air space in the secondary. Specifically is there any detriment to putting 19 Litres in a 23 Litre carboy.

Thanks

Rudeboy

The amount of airspace is inconsequential.

Any minor fermentation will produce CO2 and expel the air.

if fermentation is completed and the beer is not expelling a large amount of co2, increased amount of space in the carboy will increase the risk of contamination. however, with proper sanitation and an airlock, it is unlikely that you will get contamination with even a tiny bit of co2 being pushed up (which it does for quite some time after fermentation is "complete."

that being said with 19L in 23L, you have nothing to worry about anyway.

The concern that some people have with not filling your carboy (secondary) is that there may be a lot of O2 in all that headspace, and it may stale your beer. However, this concern is highly exaggerated. As Bill mentions above, much of that O2 will get driven out of the airlock by your beer and it can't get back in. Also, what does remain in the carboy is going to get forced to the top (CO2 is heavier than O2, so it will form a protective blanket just above your beer). Finally, if any O2 does happen to diffuse through that CO2 into your beer, not to fear -- you have lots of very active yeast in there and they will VERY quickly scavenge that O2 and metabolize it.

This beer thing is just amazing!

Somebody oughta bottle this stuff, oh wait.....
Norm

Thanks all. I've been brewing with Brew House kits and initially I was paranoid about taking any of the trub and was leaving lots of liquid in the bottom. So I had a good 4 inches headspace in the secondary. My LBS guy was adamant that I had to have it filled up to within an inch of the top or I would get oxidization. Good to know that's not really the case.

Rudeboy

P.S. It's probably it's an academic question as the bug as bitten hard and I think I'll be getting a 19 L carboy soon anyway. Still good to know.