A glass carboy is one of the most essential tools for anyone interested in brewing at home. Proper fermentation is a primary step and it’s essential that the liquid doesn’t get contaminated by outside air. There are two primary ways of making this happen. One of the challenges is to allow the carbon dioxide that is formed to escape while not allowing airflow in the other direction.
The glass carboy in itself is very tough and resists corrosion so that it will last you a long time after purchase. Plastic carboys are less popular. They come in many sizes ranging from one gallon to 6.5 gallons. The former is called a jug. Another common term for glass carboys is “demijohn.”
It’s well to remember that the glass carboy is not to be used for secondary fermentation. The latter process can take place in the final bottle itself. Depending on what it is you’re trying to brew, there are different temperatures at which the carboy must be kept. Lager for example, needs to be fermented at a much cooler temperature than ale. You must be prepared to let the process last for a few days at least.
It’s important to do some research regarding the particular brew that you’re trying to ferment in your glass carboy. This will ensure that it doesn’t get spoilt.