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Passion for Homebrewing

I was speaking with Chris and workshopping ideas for an article and we came up with an interesting topic on, How Do Hop Cannons Work? The fact is, I ordered a hop cannon this month, and it seemed appropriate to write about them.

I’ve worked with a few different designs of hop cannon over the years, and even used a Braukon hop cannon. This is the original which all other cannons are based off. Hop cannons are used for dry hopping beer.

Brewers dry hop beer to add aroma to beer. Adding hops on the cold side (after the wort has been chilled) prevents hops from volatizing and the essential oils from evaporating out. The net result of dry hopping is added aroma without any additional bitterness.

How Do Hop Cannons Work

Braukon Hop Cannon

Although there are brewers who believe, including Scott Janish if the IBU of the beer is below 30 IBU’s, dry hopping can increase bitterness. However, I digress let’s start with traditional dry hopping methods.

Traditional Dry Hopping Method

The traditional dry hoping method is to open a port or manway of the fermentation vessel and literally dump the hops in to the wort. Brewers have different processes and thoughts about when to add the hops, but the actions are still the same.

This method is the simplest way to dry hop, but it presents two major issues which are oxygenation and safety. Dumping the hops in like this, can cause the dreaded “hop volcano”.

Dry Hop Volcano!

A hop volcano happens because CO2 produced during the fermentation breaks out of suspension due to nuclearization, by the addition of hop matter. It’s like adding mentos to Coca-Cola.

When you dump hops into the beer it’s often a race to close the fermenter port/manway before beer rises and sprays everywhere.

Now, there are ways to counteract a hop volcano like adding a few pellets first, then closing up the FV and then adding the rest of the hops later. However, as you can see from the video it dangerous, especially if when using a ladder.

Oxygen Pick Up

The other issue is oxygen pick-up. If you’re adding hops after the end of primary fermentation, opening the FV up can allow oxygen pick up.

Oxygen pick-up is deadly to beer. If you’ve had a beer which tastes like cardboard, then you’ve had oxidized beer. Also, opening the FV increases the risk of particulates entering the brew too.

One way to counteract oxygen pick up is to add the hops just prior to end of fermentation.

This helps in the following ways:

  1. There’s still some primary fermentation to go, so more CO2 to be produced, this can help avoid oxygen pick up after opening the FV.
  2. As there is still movement in the beer due to active fermentation, it can help mix the hops allowing for better aroma pick up.
  3. There’s a belief dry hopping before terminal gravity guards against hop creep too.

Now, of course there are downsides to adding hops before the end of fermentation, it can increase the chance of a hop volcano. Plus, if the fermentation temperature is too hot, some brewers believe it leads to undesirable aromas.

The hops are usually left in the FV for 4 days, if you leave them for longer, undesirable grassy aromas can form.

The hops are usually dumped from the bottom of the FV outlet to the drain. In some countries though, you need to collect the spent hops for proper disposal.

Due to the above issues with traditional methods of dry hopping, brewers were seeking alternative methods, leading to the invention of the hop cannon.

How do Hop Cannons Work? What Is a Hop Cannon?

Before we look into how hop cannons work, I think a little explainer of what they are is advisable. A hop cannon is a piece of brewing equipment to effectively dry hop your beer in a closed-circuit environment.



The hops are placed inside the cannon, they are on the outside of a stainless-steel candle which act as a filter. So, when the beer is introduced and recirculated it then flows back to the FV, with the hop matter is contained in the cannon.

You run the cannon recirculating the wort, for a minimum of four hours, testing the beer throughout for sensory analysis. When you have the desired aroma, you can stop the recirculation of the beer through the hops and push all the beer back to the FV with CO2.

It means the desired hop aroma is added in one day rather than 4 days with traditional methods. Plus, as this process takes place in a closed CO2 circuit, there’s much less oxygen pick up than with traditional dry hopping methods.

You can push the beer back to tank with CO2 added to the top of the cannon

Article by Brew Me A Brewery