Suppose you want to make sure your fermentation doesn’t stall halfway through and you want to get a good head start on yeast growth during the initial phase of fermentation…
… well, that’s were good aeration comes into play…
After you boil your wort and cool it down to yeast pitching temperature you want to find a way to get oxygen into your wort… There are three main ways to get oxygen into your wort, splashing, agitating and direct injection.
This is possibly the best ‘free’ method of aerating your wort. In essence what you are doing here is splashing your wort into your fermentor by pouring it hard from the kettle into your bucket. If you are using a carboy to ferment, you can pour your wort into your bottling bucket and then siphon into the carboy.
This is the method I use most frequently and has given me consistent results for low and mid-range gravity beers.
The only drawbacks to this method is that it requires a strong back to lift the kettle and splash the wort into the fermentor and it becomes exposed to airborne bacteria. In other words, this is something that should be done indoors where you can be certain the environment is mostly dust-free.
If you can’t quite lift a bucket or a kettle to splash it, you may opt for agitating the wort instead. There are many different variations, but basically the best one is to place the lid on your bucket and shake it back and forth to ‘agitate’ the wort.
If you are using a carboy you’ll want to place a loose fitting cap or some sort of plug in the mouth of the carboy to shake it without getting the wort all over the place… most importantly, you want to place the carboy in a padded or cushioned surface area so it doesn’t break.
Rocking the fermentor is not as hard on your back, but it does require some arm strength and can be exhausting.
I like to combine the splashing and agitating techniques to get more oxygen into the wort without having to invest money in an aquarium pump or some sort of air compressor.
Another variation to agitating the wort is to use a steel whisk to whip the wort a few seconds until foam starts to foam on top… Some say this can keep your beers from getting good head formation and retention, but I haven’t noticed any negative effects on my beers.
The most efficient way to add oxygen to your wort is to inject pure oxygen directly into it. This means you must invest money into your brewing hobby and constantly replenish your source of oxygen, which is often times not needed unless you are brewing high gravity beers.
You can instead opt for injecting your wort with air using some sort of air compressor and having a sanitized tube deliver it to the bottom of the wort. The important part here is to make sure that the air or oxygen is evenly distributed throughout the wort.
If you just blow air into the wort, chances are the air bubbles will be too large and won’t dissolve into the wort. To avoid this, you’ll need some sort of diffuser like an aquarium air diffusion stone. Another thing to keep in mind is that bacteria may not survive in a pure oxygen environment but they sure can live in pure air, which means you’ll want to have an air filter in your aerating system. A HEPA filter is recommended.
So if you don’t want to spend any money, the first two techniques are great and work pretty darn well… but if your back or arms can’t handle the task, then injecting may be the way to go and it can be fairly inexpensive if you use aquarium tools to get your air source.