Introduction
An airlock is a very important part of the brewing process especially when aging a beer or something similar in a carboy. The aging process for some beers can take several months and the only thing between the beer inside the fermenter and the air outside is the airlock. If the liquid in the airlock dries up, then air and airborne microorganisms will get into the carboy and mess up the beer for you. This is a good way of making malt vinegar. But if you want to drink the beer, keeping liquid in the airlock is, therefore, very important.
Another way an airlock can fail is that it can suddenly decide that it wants to be somewhere else. The rubber stopper holding the airlock in the mouth of the carboy can slowly extrude itself from the carboy mouth – a bit like toothpaste. This is particularly true when using the more modern universal style of stopper made in a shell of hard rubber as shown in the picture below. Some residual sanitizer on the bung can greatly assist with the bung’s escape, too. Using a solid rubber stopper helps but these, too, can pop out.
This problem normally occurs immediately after putting the beer into the carboy and some moisture can get onto the neck of the carboy. Sometimes I’ve had to push a bung back into the carboy 10 or more times before it finally ‘sticks’. Once the bung seems to be staying put, don’t be fooled. It can stay there for weeks before then deciding to pop out. Once the stopper has removed itself from the carboy, it will sit on the floor next the carboy with a big grin on its face and not looking guilty at all. Meanwhile air, bacteria, molds, insects, spiders, mice, snakes, fish, frogs and all their little friends will have had unimpeded access to your otherwise potentially award-winning beer. It takes a long time before an airlock will dry up and if we let this happen, it really will be our fault. When a stopper pops out, it’s never our fault and it occurs without warning and much bigger things can now get into your beer than just microorganisms.
So, what can we do about this? This matter might sound trivial or even silly, but I can tell you that losing the airlock from a carboy will not improve your chances of winning that next competition. It’s, therefore, a very serious issue that needs serious resolution.
I’ve experimented with bits of wire, string, tie-wraps and elastic bands and while I’ve generally had success with these, they are far from being practical or being very easy to use.
A much better approach is to design and develop some sort of clip to hold the stopper in place.
Initial Ideas
It’s difficult to find a ready-made clip that will fit over a rubber stopper and stop it from popping out of a carboy. There appears to be nothing listed on homebrew supplier websites or even on the almighty Amazon, so it looks like something will have to be specially made. While using big hammers and saws to cut up little bits of material is attractive and manly, making this clip out of plastic looks like an ideal project for a 3D printer.
It looks like I’m not the first to identify the need for such a clip or to use a 3D printer to make it. Take a look at the following links to see how others have approached such a design using a 3D printer.
- https://www.thingiverse.com/thing:2818624
- https://www.thingiverse.com/thing:2519414
- https://www.thingiverse.com/thing:3495978
- https://www.thingiverse.com/thing:3588258
- https://www.thingiverse.com/thing:2474430
These all seem to take a similar approach in providing a fixed dimension housing that goes over the stopper and under the rim of the carboy mouth. The last one on this list, clamps completely around the stopper and carboy mouth and so should be very reliable. The others look as if they could easily fall off.
I’ve found that the rubber stoppers I use can vary greatly in height when inserted into the mouth of a carboy. This is because of differences in the sizes and brands of stopper, the diameter of the airlock tubing being pushed into the stopper and even the diameter of the carboy’s mouth can vary. So, I want a design that can accommodate variations in the height of the top of the stopper above the carboy mouth. It would also be useful to apply sustained pressure to the top of the stopper so that it will (hopefully) stop all movement of the stopper. This means that what I really need is some form of spring clip rather than a fixed dimension housing.
Final Design
After some experimentation trying to modify a collection of ready-made clips – including those for clothes’ lines, I finally decided to make the clip I wanted using a couple of 3D printed plastic parts and three small springs. The idea was good and the clips I made do a very good job.
They appear to fit over a range of different styled shoppers: solid and universal, different sized stoppers: #6. #6.5 and #7 and different glass carboys: 2-gallon, 3-gallon, 5-gallon and 6-gallon. I don’t know if they will work with a plastic carboy. They are robust and easy to use.
Of course, the main issue for may readers would be access to a 3D printer. Many libraries and educational facilities may allow access to a 3D printer. There are many online contractors that would print these parts for you, too.
The construction and operational details are not given here but can be downloaded as a assembly resource package using the button below.
Licensing
This project is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
This license means that the information on this website for this project is free to download and use for non-commercial purposes. If any content or derivation of that content is published, then an acknowledgement should be included referencing the original developer – me (Andy Tipler).
If you want to make money out of my efforts, please contact me via the email address at the base of this page for an initial discussion .
Assembly Resources
The following downloadable resource file contains details on how to build your own Airlock Clips:
- Full and detailed instructions on how to build this Airlock Clip
- STL file for 3D printing the upper clip
- STL file for 3D printing the lower clip
- A Fusion 360 modifiable CAD file containing the original design (other formats available on request)
This information is provided completely free for non-commercial use. However, it does cost me money to make and test these devices and to maintain this website. If you would like to further encourage me in this activity, please consider making a donation below – your support will be much appreciated.
Final Thoughts
I have now built several of these retainers – they really do work well and are easy to use. Once you have the 3D printer up and runnings, it’s probably a good idea to bang out several of these. They would make great presents for other brewers.