Carboys are rigid containers that are primarily used for transporting liquids, often water or chemicals. You can also use them for in-home fermentation of beverages, like beer, wine, mead, or cider. Carboys are usually sealed with carboy caps to prevent bacteria and oxygen from entering during the fermentation process. A bung is partially or wholly inserted inside the container to act as a seal.
Both carboy caps and bungs are used for sealing containers of beverages. But they are different. While carboy caps cover the surface or mouth of the carboy fully, bungs look cylindrical, and they are inserted into the container to serve as a seal.
What is a carboy cap?
Carboys which is also known as demijohn or carbuoy, are glass jugs that are pretty similar to water cooler bottles. Brewers use them for making beer, wine, hard cider, and mead. There are different sizes of carboys. A glass carboy does not give room for oxygen to pass through and change the beverage inside. The effects that oxygen has on beer, wine, mead, and cider after fermentation is not so good. Carboys are very durable; you can use them for a very long time.
Carboy caps help to cover carboys as an alternative for regular stoppers. They usually have two spouts; one is meant for facilitating a blowoff hose and the other for an airlock. The two openings are convenient for attaching or inserting tubes, airlocks, siphons, or racking canes.
With carboy caps, you are free to attach a racking cane directly through the lid. If you combine it with a CO2 tank or other methods to slightly pressurize the vessel, you can pump your homebrew efficiently for racking into another container. This makes it a dual-purpose tool to add to your brewing setup.
Make sure you use the right-sized cap for your carboy. Orange carboy caps are for 3, 5, and 6-gallon carboys. The dark red carboy caps are for 6.5-gallon carboys.
There are certain things you should know about when using a glass carboy in your home brewery.
Using a carboy as a fermenter
It will help if you practice proper hygiene when using a carboy as a fermenter. You can use a solution of one tablespoon of bleach for a gallon of water as a great sanitizer. You don’t need to bother about the bleach aroma affecting the beverage in the carboy because carboys don’t absorb any bleach aroma and can be filled in advance.
A carboy that is used as a fermenter should have some headspace. A 6-gallon carboy can serve as a fermenter for up to 5 gallons of homebrew.
There are some accessories you will need for your carboy. Check them out below.
- Strainer
- Special brush to clean it
- A handle (install under the lowest bump on the neck)
- Stick-on thermometer
- A milk crate (handy for moving carboys and keeping them off rough floors, like concrete)
- Blow-off set-up
Always make sure you don’t keep a filled carboy in a place that is not clean and smooth. This is to make sure you don’t create any pressure points that may likely crack the glass. You can place your carboy on a flattened piece of cardboard or a towel, or a rug.
You may not have plenty of headspaces if fermentation is underway. Plus, foam can eventually clog the stopper or airlock. When that happens, enough pressure can build up to crack the carboy. As soon as foaming stops, you can leave the blow-off in place or exchange it with a stopper and airlock.
Always strain out whole or leaf hops when you ferment in a glass. For hops that don’t end up clogging the stopper or blow-off, they will end up clogging your racking cane. A stick-on “fermometer” is a great accessory. Place it below the three-gallon mark so that you can see the temperature as you top it off. After that, you can then change the temperature of the water to hit your target pitching temperature.
Always keep your beer covered when it is in a clear container. If you expose it to UV light, it will give it an unpleasant aroma. You can use a paper bag with a hole cut in the middle of the bottom.
Using a carboy for secondary fermentation.
Fermenting should take place in the fermenter. But sometimes, there will be some fermentation happening slowly, so a carboy with an airlock is the perfect place for that to happen. Some beers don’t need to undergo secondary fermentation. If you are learning to brew or brewing ale with less than 5% alcohol, the secondary is not compulsory. But there are some styles of beer that need to undergo secondary fermentation, so they come out well.
You can bottle or keg your beer when it is convenient for you. It would help if you used a carboy for secondary fermentation that you can quickly fill up. If you make five gallons of brew, use a five-gallon carboy for secondary. You can also fill it with sanitizer ahead of time. I like to rack the sanitizer I use on brew day to fill the carboy that I’ll use later.
Keep your carboy covered in a dark place. If light hits the beer, it will create an unmistakable skunky aroma. Also, don’t forget to check the airlock when you are doing long-term secondary fermentation.
If you want to start your siphon, put your racking cane into the middle hole of the cap. Then, blow into the other hole. Air pressure on the liquid will force it up the racking cane, thus starting your siphon.
Capturing yeast or fermentation overflow
Do you want to avoid spills from a vigorous fermentation or collect top-fermenting yeast for reuse in another batch? Insert a racking cane into your carboy through the center hole of your carboy cap while leaving the other hole closed. Cap a small overflow vessel (like a 3-gallon carboy) and run a tube from the racking cane into the side hole on the cap on the smaller container. Insert your airlock into the center hole of the overflow vessel’s cap.
What is a Bung?
A bung which is also called a stopper or cork is a cylindrical or conical closure that is used for sealing a container, such as a bottle, tube, or barrel. Unlike a lid, which encloses a container from the outside without displacing the inner volume, a bung is partially or wholly inserted inside the container to serve as a seal. A bung is just like a plug or closure that is used to close an opening in a drum or barrel. But it is called a plug when referring to a steel drum closure. A glass bung is called a “ground glass joint” (or “joint taper”), and a cork bung or stopper is called a “cork.” Stoppers used for wine bottles are referred to as “corks,” even when made from another material.
A famous example of a bung stopper is the cork of a wine bottle. Other bungs, especially those used in chemical barrels, may be made of metal and be screwed into place through threading.
What is the difference between a carboy cap and a bung?
Bung is the hole in the head of a cask, keg, or barrel. It can also refer to the hole in the belly or bilge of a cask and the devices that seal those holes. The average size of a cask or barrel bung is about 15 to 16 inches, but some breweries use smaller sizes.
A bung, when used as a closure, it is hard nylon, rubber, or wood stopper used to plug the hole in the head or belly of a cask or keg. It is usually hammered in to be flush with the container. But in traditional English cellaring, the bung refers mainly to the hole in which the keystone is inserted in the cask head, and the shive boss is in the belly of a cask.
A carboy (or carbuoy), also known as a demijohn, is primarily used for packaging liquids, or beverages, or water. They are also used for in-home fermentation of drinks, mostly beer or wine. In brewing, a carboy or demijohn is a glass or plastic vessel used in fermenting beverages like wine, mead, cider, perry, and beer. It is often fitted with a rubber stopper and a fermentation lock to hinder bacteria and oxygen from entering during the fermentation process.
Carboy caps help to cover carboys as an alternative for regular stoppers. They usually have two spouts, one to facilitate a blowoff hose and the other for an airlock
So, the significant difference between carboy caps and bungs is that carboy caps cover the carboys completely while bungs are inserted into the bottle to seal it.
Conclusion
Carboy caps and bungs are two instruments that are used for sealing beverages. While bungs are inserted into the containers for sealing, carboy caps usually cover the entire surface of the carboy. Most winemakers make use of bungs for sealing their wine bottles.
Whichever one you decide to use, ensure you carefully do it, so you don’t make mistakes and ruin the liquid in the containers. Also, ensure you properly sanitize whatever you would be used during production. This is to avoid oxygen or bacteria from affecting your beverage.,