When I started brewing Belgian beers I really wanted to be able to carbonate above what 12oz bottles take. I don't have the cash for a floor corker and I don't believe any HBS around me have them for rent. I remember reading a lot of sources that said those plastic champagne corks would and
would not work. I do want to clarify that plastic corks do work for both Belgian bottles and of course champagne bottles.
Here's your proof:
I have these bottles of saison carbonated at about 5.5 vol. They come out delicious and nicely carbed.
What I will say is that it is an imperfect solution. It looks nowhere as nice as an actual cork. More importantly, as you can tell between these two pictures, the corks do not sit flush on the lip in all cases. If you look on the second picture you can see that the cork is pressed up. The problem I accidentally discovered is that if you press on the cork it releases the pressure and beer starts to foam out the sides. I assume a bottle where that happened will go flat. The one time I had this happen, I went ahead and opened the bottle and drank it.
I looked at some champagne bottles of sparkling agave mead I recently bottled and I see the corks are starting to push up against the cage and away from the glass as well. I have turned both the champagne and Belgian bottles upside down, shook them, moved them, etc. and even the bottles with the cork pushed up do not leak. It is only when the cork is pressed down. So anybody who gives this a go needs to be careful with the bottles. I'm not sure if that pressing up is a product of inexperience working with the cages and not tightening them enough but it seems like the plastic corks just aren't tall enough for the bottom of the cage to sit up against the bottom of the lip.
I will also say that they fit better in some Belgian bottles than others. Some are very tight but most are easy to slide in and out. When I empty a Belgian bottle from the store I clean it and test it to see if a cork will fit. So far I have only found one bottle that was too big, which was a bottle of Unibroue Quelque Chose. I have plenty of Chimay bottles and they seem to work very well. The corks go in by hand and are fairly easily pulled out. I know some people have said they had to use pliers or vice grips to get them out, but I haven't had that problem. If I found bottles that were that difficult to empty, I wouldn't use the plastic corks on them a second time.
In spite of those very minor problems, there is a lot of upside to their use.
It takes about a minute to cork a bottle. I starsan the long part of the cork that goes in the bottle, press it in by hand until it is flush with the lip of the bottle. I drop the cage over, pull the bottom ring tight and then twist it closed with a pen. It's actually much, much easier than capping 12oz. bottles and of course using bigger bottles means fewer bottles to fill and less corks to use.
I bought 100 corks and 100 cages for about $25 total at my LHBS. Considering that both can be reused (over and over) it's also incredibly cheap. I'm sure the cages will eventually break down. The seals on the corks might go out, too, but I'm sure I will get a lot of use out of them. You can actually save the cages from Belgian bottles you buy and reuse them. Just be careful about untwisting them. You may need to remove the cap on the top of the cage. I'm not sure if they will prevent getting a good tight cage. They easily pop out with a gentle push from the top.
They do hold up to pressure. As I said I have saison carbed up to 5.5 vol. in the Belgian bottles. I also have the sparkling agave mead in the champagne bottles carbed to 7 vol. without a problem. I haven't experienced any plastic taste or infection from the corks.
So there you go, proof you can use those plastic corks successfully on Belgian bottles. Just test the bottles before bottling them and be careful about pressing on the cork.