So I finally got tired of opening my buckets to take hydrometer reader (actually I use a refractormeter). I got smart and made a mini fermenter to show me what is going on in the real fermeter. The main reason I would do this is becasue I don’t want to rely on airlock activity to be a measure of my fermentation progress. I want to take gravity readings.
The first step in making on of these things is the equipment. You need a bottle, preferably clear, a drilled stopper, and an airlock. You sanitize everything the same as you would you fermenter. When your wort is put into your fermenter and combined with yeast, you take a small sample (only a few ounces) and put it into the bottle. Now you have a mini batch taken from your larger one. It is the exact same thing, and if you keep it in the same storage, it should produce the same results.
Why would you want to do this. If you are working with a plastic bucket or a carboy, it can be a pain to keep reaching into your fermenting beer to grab a sample. You run the risk of infection every time you touch it. Also, you take from the main fermenter, you can’t put your sample back into the beer. Making a small version you don’t have to worry about wasting any beer as you can use the same sample over and over since you will never be drinking it.
Another nice thing is that you can visually see what is going on; if you are not using carboy this can be a real advantage. There are a few problems with this method however. The biggest being that a small sample of liquid reacts much quicker to temperature changes then a large sample of liquid. This can increase or decrease your actual fermentation process. I think getting gravity readings this way is a good way to go and you can leave your beer alone while still knowing what’s going on inside.