This air-lock is a good choice for containers between 1 and 5 gallons in volume. Or, when a slow fermentation is expected on larger batches. With this particular air-lock you can detect even extremely slow fermentations on larger batches. Works for wine or beer. Fill approximately half way with water. The water acts as a environmental barrier keeping bugs and other little nasties out of your batch, but still allowing gasses to escape the fermentation.
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