Glass vs Plastic? The Best Fermenters for Beer Brewing

by Brad Smith on May 29, 2010 · 24 comments

One perpetual debate among home brewers is the relative advantages of glass vs plastic fermenting vessels for making beer. Most beginner home brew kits come with a large plastic pail with a plastic top. However many advanced brewers swear by the advantages of the classic 5 gallon glass carboy. So who is right? This week we take a look at them side by side.

The Plastic Fermentation Vessel (aka Bucket)

Most brewers start fermenting in a 5 gallon food grade plastic bucket. These buckets are cheap, durable and relatively easy to clean. However the plastic bucket has both advantages and disadvantages:

  • The plastic bucket is easy to clean – since the entire top comes off, you can reach in and scrub any grime off in a few minutes
  • Plastic is durable – if you do drop the bucket it is unlikely it will break, and they do last a long time
  • Plastic is harder to sanitize completely – over time it does get small scratches on the inside which can be a haven for bacteria and germs, which is why most brewers recommend replacing plastic buckets after a year or two
  • Plastic is not suitable for long term storage of beer (i.e. months), as it is permeable to air
  • Many plastic buckets have a poor seal between the bucket and cover – which can result in air being introduced as well as the brewer thinking fermentation is done prematurely (as the airlock has stopped bubbling due to the leaks)

The Glass Carboy

In the other corner, we have the 5 gallon glass carboy. A carboy is a large water bottle made of real glass, and usually comes in either a 5 gallon or 6.5 gallon size. Glass carboys are obviously far less durable, but are the favorite of many advanced brewers. Some advantages/disadvantages include:

  • Impermeable to Air – Air cannot penetrate the glass, so you can leave your fermented beer in a glass carboy for months without worrying about it being spoiled by aeration. Also you don’t have to worry about leaks through the top as a proper stopper will form an air-tight seal.
  • Easy to Sanitize – Glass will not pit or scratch like plastic, so you don’t have to worry about scratches creating havens for bacteria. Further, as the glass is transparent it is pretty easy to see if it is completely clean.
  • You can Watch Your Brew – While not a huge deal, many brewers like being able to see the beer as it is fermenting to get an idea of the size of the Krausen layer, how active the fermentation is and how much sediment has formed.
  • Harder to Clean – After fermentation is complete and you have transferred or bottled your beer, it can be harder to clean a glass carboy than a plastic bucket. You need a large bottle brush to do it properly and even then you may find some areas are more difficult to reach with the brush than others.
  • Easy to Break – I’ve broken at least three carboys inadvertently, though thankfully I have not yet broken a full one. However, carboys are difficult to lift and maneuver, and will shatter if you bump them against any solid surface. Breaking a full carboy can be a safety hazard as well as a huge mess. I try to arrange my brewing setup so I move my carboys as little as possible once they are full.
  • More Expensive – Carboys are more expensive than plastic fermentation buckets, and you also need to consider that you may break a few during your brewing career.

The Bottom Line

So which is best? I personally use glass carboys for both stages of my fermentation, and have for the last 15+ years. Why? I had some bad experiences early on when I thought my fermentation was complete, but instead found I merely had a leaky seal on my plastic bucket. In addition, I like the security of seeing my beer ferment, knowing the fermenter is completely clean and sanitized and knowing I can leave the beer in the secondary as long as I want (sometimes I get busy) while still maintaining a seal. However, the choice, as always, is yours!

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