I remember seeing a post about this, though I can't remember whether it was here - I couldn't find it, efficiently, nonetheless.
In case anyone has trouble keeping the bung/stopper in the top of glass demijohns/carboys, I made simple muselets out of 16 AWG craft wire.
How-To images follow the 'deployment' images.
Fermentor (apologies for the poor lighting, but you know, fermentation chamber.
![](https://img.fae.ro/d9e2b9.jpeg)
Aging a mead, or any secondary.
![](https://img.fae.ro/5fd140.jpeg)
HOW TO MAKE IT:
1. Cut craft wire, approximately 2 feet, folded in half.
![](https://img.fae.ro/b52fe2.jpeg)
2. Twist a loop into end - at middle fold - a few times. I do this so that the loop will end up just below the top of the bung.
![](https://img.fae.ro/da420c.jpeg)
3. Place wire about demijohn neck, where you will want it to set (has to be under a lip, obviously).
![](https://img.fae.ro/31b696.jpeg)
4. Wrap around and CAREFULLY pull the wire tight (should do this while demijohn is empty, just in case).
![](https://img.fae.ro/80c9b1.jpeg)
5. Twist pair to close.
![](https://img.fae.ro/258440.jpeg)
6. Place bung. Loop ONE of the wire ends over the bung, slightly off-center, and thread through the loop.
![](https://img.fae.ro/af7966.jpeg)
7. CAREFULLY pull the wire tight, and kink the pair to set.
![](https://img.fae.ro/85a9b6.jpeg)
8. Lay second wire end over the first and the loop.
![](https://img.fae.ro/3b014c.jpeg)
9. Pull second wire-end tight, and twist to set.
![](https://img.fae.ro/82210d.jpeg)
ALL DONE!!!
You can see there's plenty of room for an airlock. I normally only use the drilled stoppers, and not the type used in this demo - they are WAY more reliable, in my experience.
![](https://img.fae.ro/dc2fb1.jpeg)