Plastic Vs. Glass Carboys

For this tutorial we touch on the age old debate of plastic versus glass. In this article we’ll touch on the advantages and disadvantages of both and let you come to your own conclusion on what is best for you and your home brewery.

Plastic carboys

Plastic carboys are one of the options available to homebrewers as fermentation vessels. Plastic carboys are more affordable than their glass counterparts. For a homebrewer on a budget, this can be a major deciding factor. Through most home brew suppliers they run 25-30% cheaper in fact. On top of that, shipping will be more affordable when buying online.

Plastic is far and away lighter than glass. This may not seem like a big deal at first, but what happens when you fill it with 50-60 pounds of beer? That weight adds up pretty quick. Carrying a more manageable weight decreases the risk of dropping said items. Glass carboys can be dangerous when dropped, due to the positive pressure and fragmentation of glass when it breaks.

If you were to drop a plastic carboy, it may break from the drop, no different than glass. The difference here is that it won’t leave shards of sharp glass all over your floor.

Oxygen permeation becomes a factor with plastic. While minimal (you add more oxygen to your beer by removing the bung once than the amount of time your beer is in the carboy), oxygen does leach through the walls of the carboy.

To remove oxygen in the headspace, especially for wines, some brewers will use a vacuum pump over the mouth of the carboy. Plastic isn’t strong enough for that kind of reverse pressure and may implode. Traditional glass carboys can handle this pressure.

Plastic is well known to be softer than glass. When cleaning a traditional carboy, you’ll find that krausen and hop gunk gets stuck to the roof of the carboy. A carboy brush cannot be used on plastic carboys as it will scratch the plastic. PBW or a similar product must be used to clean them. While these products work well they are even more effective with a brush.

Glass CarboysGlass carboys

Glass will not permeate oxygen through its walls. This can add peace of mind to a brewer aging sours or other long term beers. It is also more resistant to heat, although you shouldn’t add hot liquids to either glass or plastic containers.

Glass will not scratch after heavy use, making it easier to clean and maintain. When glass has an unseen molding defect, it will usually be smooth and won’t harbor bacteria. Glass is also a safer option to sanitize and use for regular beer after brewing sour ones (however it’s easier to just have separate fermenters for sour fermentations).

Glass is completely inert which guarantees that no chemicals will ever leach into your product. While plastics graded for food production should also be free of any harmful leaching as well, can you ever be too safe?

Glass carboys come in 1 gallon sizes which are ideal for smaller batches of beer or mead.

So we’ve gone over plastic and glass. Now let’s look at some overall good tips for carboy management.

  • There are now wide mouth carboys available in both glass and plastic that make it easier to clean.
  • Sliding carboys across the floor or even placing them directly on hard floors will increase wear and may eventually cause breakage. Place something like an anti-slip mat where you will be putting carboys.
  • A full carboy is heavy. Don’t lift them by the neck as the necks may break off. If you have a carboy handle that attaches to the neck, lift from the bottom and the handle. Alternatively, you can place carboys in milk crates which make them a bit more mobile.

Now you have the knowledge to make a solid decision when it comes to carboy selection. Just remember that you don’t have to go just one way or the other. A different carboy might be suited to different brewing needs, so don’t be afraid to mix it up.

written by David Doucette

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