May 27, 2010

Double drop fermentation

So I've been reading some books about British pub beers and, in particular, the vaunted British Bitter. Needless to say, I was inspired to recreate the technique of the Brakspear brewery, which produces some of the finest brews in the UK. They use an interesting technique known as the double-drop fermentation and claim it produces unique flavors, especially in their Bitter.


6 lb. Crisp Maris Otter
.75 lb. Simpsons Medium Crystal

Target OG 1.038

Mash 1 hour at 153 degrees

60 Min 1 oz Fuggle (4.8 AA)
15 Min 1/2 oz East Kent Goldings (7.2 AA)
1 Min 1/2 oz East Kent Goldings (7.2 AA)

Wyeast 1275 Thames Valley (Brakspear Bitter strain)

The theory of the drop fermentation is to by gravity drop the actively fermenting beer from one vessel to another. Brakspear states that they ferment the wort for roughly sixteen hours in one vessel, then they open the tank and drop the fermenting wort vigorously into another fermentor to complete the active fermentation. Now you may say that this could cause oxidation in the beer, but because the wort is very actively fermenting at the time of the drop, the additional oxygenation and the rousing of the yeast actually enhance both the fermentability of the wort and flavor of the finished beer.

Most homebrewers have the capability to recreate such a fermentation process at home, with little to no additional equipment. I started the fermentation in my bottling bucket with spigot, and decided to live on the wild side by leaving the vessel open to the air for the first sixteen hours.

On my brew day I pitched the yeast at four o'clock in the afternoon, when I woke up the next day at eight in the morning there was a nice active krausen on the beer.

Next, I sanitized my six gallon carboy, a funnel and a couple feet of half inch siphon hose. I set up the bucket on my counter, the carboy on the floor with the funnel and attached the siphon hose to the spigot. Open, drop, and let it rip!

At the time of the drop, my gravity had dropped from 1.032 to 1.022. At the time of this post, the beer is happily fermenting away to its terminal gravity.


  1. Surely the objective with double drop as at Brakespear is exposing a large surface area of fermenting wort to the air, quickly. Your method will only expose a small surface area. As an English homebrewer I used to open ferment and rouse my wort by stirring it briskly. I had mixed results and eventually stopped rousing and closed fermented.
    I look forward to hearing about the finished beer.

  2. That's awesome! I just did an ordinary bitter in an open fermenter...No gravity drop though.

    The keg is set to be tapped June 6th....can't wait!

  3. So...what about all of that active, healthy yeast that's sitting on the top of the beer? Did that go in afterward?

    Admittedly, we're talking about a small beer. There should be plenty in the solution...just seems like a waste of good single-celled organisms.

  4. The vast majority of the top fermenting yeast did make it into the carboy, a little bit clung to the sides of the bucket. It was a cool experiment, the beer has almost finished bottle conditioning. Early samples indicate a good amount of fruity esters, final gravity was 1.009.

  5. Cool concept. I agree with Mike, that it sounds like it could have been airated better by not using the siphon hose.

    Also, I was thinking maybe only make a 5.5 gallon batch with 4.5 gallon in the primary. Where you'd then be able to "wash out" the remaining krausen & yeast with 1 gallon of fresh/sanitized water.

  6. I agree with Mike, I think the main purpose is to provide the yeast with additional oxygen by splashing it around. Meadmakers do this a lot, and the general rule of thumb I've heard is that you can supply oxygen during the first third of fermentation but should avoid it after that. There is a video of the process on Brakspear's site:

  7. Funny thing, I didn't start with the siphon hose - I added it later because the beer was splashing so much off of the funnel that it was getting everywhere, from the walls, the stove and the floor. In order to cut down on a lot of clean up and wasted beer, I added the hose to contain it. I did indeed watch that Brakspear video on their website, very cool process.