I just racked my cyser to a 3 gallon secondary and the rubber stopper that is supposed to fit doesn't want to stay put in the carboy neck. The last time I tried to age something long-term, it oxidized. Let's not repeat that. So I guess I need to buy one of these: http://www.midwestsupplies.com/carboy-cap-3-5-6-gallon-carboys.html Before I make a special order (no home brew shop nearby) just for a stupid carboy cap*, would someone please tell me if these are effective, or if there is a better way to cap a carboy? They say they are good for a range of sizes. Is that really true? In the short term, the carboy neck is triple wrapped in plastic wrap, but that is not a long term solution. *OK. I probably will not order just a carboy cap. I'll probably use it as an excuse to buy a couple hundred dollars worth of other equipment and ingredients. I always kill myself with my own bait and switch. Damn this expensive hobby.
Just remember I bought a universal bung to try after messing up the other beer I referenced. Seems to fit well. A good solution for 3-5 months of aging?
I use carboy caps on 3 and 6 gallons glass carboys. I use hose clamps around the outer edge of the cap to secure them. Once secured, they appears to be able to keep pressure. They are easy to switch between blow off tube and airlock. I don't rack through the racking port, instead I used it when purging with co2. I cannot vouch for oxygen migration through the material thought. That or any other material for that matter.
I don't like the caps. I prefer the bung style stoppers. Just use a bit of tape to secure them if they want to pop out. I wouldn't be worried about ruining a beer using a cap, as I used them in the past and never had issues, I just like the bung style stoppers better. The carboy cap is of poor design in my opinion.
My carboy cap leaks on my 6g better bottle so I put a hose clamp I bought from home depot on it to tighten it up.
I used to use carboy caps and found that I had to put a rubber band or two around the lower lip to maintain an airtight seal. With the rubber band in place they work well for blow off tubes and can work well for siphoning too. But generally I either use rubber stoppers with air locks or low budget tin foil over the carboy top.
