Glass vs. Plastic Carboys

Blow Off Tubing Assemblies

A blow off assembly is a length of tubing which is attached to your primary fermentor to allow excess yeast and foam (krausen) to escape. During an especially active fermentation, the krausen can fill the entire head space of a fermentor. Without a place for this foam to go, it can create quite a mess. An airlock can become clogged, but a blow off assembly allows krausen to be expelled from the fermentor while still making sure that nothing gets in. One end of the blow off is inserted into the fermentor, and the other end is submerged in sanitizer in an open jug or bucket. Keeping the end of the blow off tube below the surface of the sanitizer will keep a positive seal in the fermentor. There are several different types of blow off tubing assemblies depending on the type of fermentor.

A 1″ ID blow off hose fits glass carboys. 1.25″ Blow-off hose for older style Acid Carboys.

The PET Blow-off Assembly is for narrow-neck PET plastic carboy that use a #10 stopper.

The Fermenator Blow off assembly is for Fermentators

A length of ⅜” siphon tubing can be inserted into a bucket lid by removing the airlock and grommet if needed as well.

The Fermenting Process

The Fermenting Process


To provide an environment in which the yeast can accomplish a healthy and clean fermentation.

You’ll Need:

Your primary fermenter, blow-off assembly, siphon, sanitizer and secondary fermenter (optional).

*Note: Checking Your Gravity

While your specific gravity will begin to drop during the fermentation period, this is an aspect you should trust and not necessarily test. You want your beer to be exposed to as little possible contamination as possible. Every time you unseal the airlock, this exposure occurs. A good rule of thumb, measure your original gravity prior to pitching your yeast, then at any time you might transfer your beer, either to another container or, finally, during bottling/kegging.


Primary Fermentation

Within a day or two of brew day, fermentation begins. As the yeast convert malt sugars into CO2 and alcohol you will see bubbles come through the airlock. The specific gravity will steadily drop and a cap of thick tannish foam called krauesen forms above the beer.

You may want to store your brew in an area that is easily cleaned, a particularly violent fermentation could cause a bit of a mess. Violent? Yes, violent. As with anything that builds with increasing gas levels, explosions can occur. Explosions are most common if your airlock fills with gunk essentially stopping the flow of gas out of the carboy. If your krauesen starts filling your airlock. You may want to initiate a blowoff set up.

Roughly one to two weeks from brew day, fermentation ends. Bubbles coming through the airlock become very slow or stop entirely, the specific gravity is stable and the cap of foam starts to subside.

Secondary Fermentation

During our fermentation process, we see a layer of krausen form atop our beer, where does it go? That krausen normally dissipates over time and any remaining grain particles, hop particles and dead yeast cells will accumulate instead at the bottom of your fermenter in a mass known as “trub”.

While sitting on this trub for a short while can impart flavors we want to see in a beer, letting our brew sit atop this trub for too long can create flavors we don’t want. To avoid these flavors setting in, we will “rack” (siphon) the brew out of the first fermenter, careful to leave the trub behind and into a new, clear and clean fermenter. Doing so allows the brew to settle out and condition in flavor. It also give the brewer an opportunity to clear out the beer, after racking the beer into a secondary fermenter, still more trub may form, but when racked into bottles during the final stage the beer should be less hazy and more clear than it started off.

Remember, when racking into a new, secondary fermenter, it is equally important that this vessel is clean and sanitary. Be sure to sanitize your auto-siphon, your carboy, your airlock and stopper and any tubing that may come in contact with the brew.

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