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Airlocks TGIF

Published: 12/09/2014 12:36 pm

HBS Owners know it’s going to be one of “those” days when they are greeted at the door before opening time by a red faced gentleman holding an airlock in their hands. It's usually followed by demands for a replacement unit if it was new or sometimes a request for replacement yeast etc.

I’m going to go out on a limb here, but please bear with me.

Perceived airlock problems are THE #1 reason why the phone rings or a customer gets frustrated in Home Brew Shops. You won’t need to take a pill if you can grasp 4 simple concepts about airlocks.

Here we go – grab a beer.


  1. Airlocks were designed by some multi billionaire somewhere on the other side of the world as his pet project and legacy to the world of brewers knowing full well, that for generations to come, brewers would pace the room in circles for days, like an expectant father awaiting his first born child’s appearance. In the early days, the original airlock concept was known as a Harsch crock. They probably still should be called that.

  2. Airlocks are designed to allow gas to escape, keep bugs, dust bunnies, budgies and oxygen out and absolutely nothing meaningful beyond that concept.

  3. Bubbling of an airlock does not absolutely mean the brew IS fermenting

  4. Lack of bubbling of an airlock does not absolutely mean the brew is NOT fermenting


If you feel some deep, dark, meaningful and secret desire to sit and watch bubbles of yeast farts rising through a thimble full of water, then so be it, we support your choice and respect your right to be an individual.  But, there are a few other things you should know first.

  • Airlocks can bubble because the air in the headspace has warmed, expanded and needs to escape.

  • Airlocks can bubble when the yeast is in the Log Phase, having a reproductive orgy in your beer and produces a little CO2 – but it is not fermenting yet.

  • Airlocks can bubble when the yeast have finished fermenting and are currently going all psycho-cannibal on each other in a process known as autolysis -The beer was done ages ago and the 300 billion yeast cells are self-destructing. It’s kind of like an in-laws family reunion but with single cell organisms. OK, it’s exactly the same.

  • Airlocks are designed to be the path of least resistance for gas. Do not over fill them lest your seals will allow the gas to escape without you being privy to the entertainment of bubbling activity.

  • Airlocks should have a couple of drops of sanitiser placed in them as well. It'll save some heartache later when an acetobacter infection turns your pride and joy into 23L of balsamic dressing.

Take a walk on the wild side.

There is an obscure skinny arse glass tube like thing called a beer and wine hydrometer.

Hydrometers make great pets for brewers. They do not need watering; they stay where you leave them, never chase the postman and never deliberately lie. Their only bad habit is that they need about 100ml of beer before they tell you what the specific gravity is. That makes them a lot cheaper to keep than my dogs plus hydrometers do not bark at 3am.  Oh, and it will not defecate in your beer unless you get lazy and drop it into your fermenter to save the 100mls without first cleaning and sanitising it. Oh they are however, prone to being broken when you use the dust case that it came with as a test tube and the bottom cap falls out when you do a test.  Don't be a scrooge. Get a test tube for under 4 bucks, save yourself 9.

Hydrometers – never be without one and understand how they work - see the article HERE

Now that you have received your BAppSc (Hydrometers and Airlocks), go try it on a beer. Use the hydrometer to take a reading when you first mix it and before the yeast goes in. If the reading changes when you use your hydrometer to check for fermentation (because the airlock is not bubbling) say, 48 hrs later, then it is a positive sign that the yeast are working.

When you get at least 2 hydrometer readings that are unchanged a couple of days apart and the reading is about where you expected the gravity to finish, then your yeast is done and the beer is fermented.

Do I use airlocks? Yes - Sometimes I use them as a door jam. I even use them sometimes for beer, cider making or for mead making. (sometimes)