Plastic vs Glass Fermentor: Which one is Better?

Taking proper care of the fermentation process is essential if we want to achieve a good and healthy beer, and the fermentor we use, be it plastic, glass, or even stainless steel, plays a hugely important role in it.

However, which one is better since, after all, they are all priced quite differently, so how do you know which one to choose?

In this article, I will mainly be comparing glass and plastic fermentors and which one is going to suit your needs better?

But first, I think we need to talk about what a fermentor really is and what it does before moving on to the actual differences between them:

What is a Fermentor?

Fermentors are vessels made out of food-grade materials, such as PET Plastic, Glass, and Stainless Steel so that beer can be produced safely within them.

The fermenters must have enough volume capacity to house the necessary amount of wort to be produced (converted into beer) and should at least have 10% free headroom to account for the Krausen.

For example, if we have 20 liters or 5 gallons of wort, we need a capacity of at least 22 liters in our fermentor.

The purpose of fermentors is to allow fermentation to take place successfully, sealing off the wort entirely from the outside world, and preventing the entry of foreign microorganisms and oxygen, which can endanger the beer.

Plastic Fermentation Bucket

They are cylindrical food-grade plastic fermentors with a wide opening at the top that provides easy access for cleaning, pitching the yeast, and adding other ingredients, such as hops when dry hopping.

Bucket fermentors also have a tap to transfer the beer once fermentation is finished which is located just about an inch above the bottom of the fermentor so that it’s slightly higher than the layer of sediment that forms after some days of fermentation, preventing it from getting transferred into the bottles.

Cylindrical fermentors allow for successful and healthy fermentation but the beer may need to be racked to a secondary vessel if it’s going to be matured in that vessel. This is done in order to keep the beer from being exposed for too long to all of the dead yeast that is in the sediment.

Fermentation vessels also have an airlock, which is a device that allows the release of CO2 generated during fermentation to the outside, releasing excessive pressure inside the vessel since not doing so could certainly increase the risk of the wort spilling everywhere, or even worse, the fermentor literally bursting (having to clean beer off your walls and ceiling doesn’t sound all that fun, does it?).

Note: Glass fermentors also use airlocks.

Some low-quality containers are not fully airtight, so the airlock is not necessary, but I wouldn’t recommend using those.

1. Large opening for easy access: Bucket fermentors have a large opening at the top that allows you to reach in with your hand as well as use brushes to give it a good cleaning, as well as for easy hop incorporation during dry hopping.
2. Plenty of Headroom: Plastic fermentors have more free space to carry out fermentation because the top can accommodate more volume compared to the narrow neck that Carboy-type fermenters usually have. Having more headroom is useful when incorporating yeasts with a vigorous starting activity, such as Nottingham, for example, which tends to generate a higher Krausen and greater risk of spillage.
3. Light and easy to transport: they are light fermentors that can be carried everywhere and can even be placed in a refrigerator with a temperature controller if the aim is to achieve a more stable fermentation.
4. Medium durability: being plastic, scratches and intensive use mean that it must be replaced periodically. Plastic is not inert like glass or stainless steel and generally causes bacteria to grow inside of those scratched areas.
5. Modifiable: Easy to modify as you can make holes, put in a spigot valve, and other necessary items, with relative ease.
6. They can scratch: scratches can harbor microorganisms that can modify the quality of the beer and even contaminate it. Scratches can create biofilms that are very difficult to remove if they persist over time. To avoid this, fermentors should be cleaned with alkaline cleaners at first to remove organic matter, and then with an acidic cleaning solution.
7. They are affordable: Plastic fermenters cost ⅓ of what glass fermenters do and even less than what a stainless steel fermenter costs.

Glass Fermentor (Carboy)

Glass fermentors are made for craft brewing and glass is a completely inert material that will never negatively affect the quality of the beer that is brewed in it.

Glass fermentors allow you to see the actual fermentation process happening since they are transparent, which is a major appeal for some homebrewers.

One important con about glass fermentors is that they are extremely fragile, and by that I don’t mean that they will burst under the first sign of internal pressure coming from the CO2 production, but rather that if you were to drop it, since they are extremely heavy, they will most likely shatter, which not only is really dangerous but you will now have about 5 gallons, or 20 liters of beer, to clean up.

Among the glass fermentors, we have the Carboy (wide base and narrow neck) which does have another drawback: It doesn’t come with a tap, so you can’t easily transfer the beer to another fermentor or bottle it directly from the tap like you would with a bucket fermentor and you might end up introducing a lot of oxygen into the beer.

1. Reduced amount of available oxygen: The geometric shape of the neck makes it so that there is much less room for oxygen, which is one of the enemies of beer.
2. They allow us to see what is happening during fermentation: being transparent, they allow us to see the fermentation taking place, how much sediment there is, if the Krausen has dropped or not, etc.
3. They are heavy and difficult to transport: They can fall and break, causing injury or physical contamination in the room (huge mess).
4. The top opening is small: This makes it difficult to physically clean the carboy, like using a brush, and the narrow neck limits the incorporation of hops or spices when dry hopping.
5. Useful for chemical cleaning: chemical cleaning is more effective on a glass fermentor compared to plastic because the non-porous surface of glass prevents bacteria and microorganisms from lodging and developing in them, favoring the removal of any unwanted material. Glass fermentors can withstand higher temperatures and can be cleaned with a wider range of chemicals that generally harm the PET fermentor.
6. They are more hygienic: Since they are made of glass, they cannot be scratched when thoroughly cleaned with a brush or steel sponge, they can also be cleaned with a greater number of products, and are easy to sanitize.
7. They are more expensive: They cost approximately 3 to 4 times more than the plastic fermentors, but it is not necessary to replace them periodically if they are not broken or have cracked, a good physical and chemical cleaning, as well as properly taking care of them, guarantees that they will last indefinitely.
8. UV Light can reach the beer: One huge con about glass fermentors is that they should be stored in a dark place, or covered with a material that prevents ultraviolet light from reaching the beer, as this can affect the quality of the beer, producing undesirable off-flavors.

Plastic Carboy

Plastic carboys are just that, fermentors made out of plastic with the shape of a carboy and share all of the traits and characteristics of both. Although it’s worth mentioning that they are extremely hard to clean since you can’t really stick your hand in to give them a nice scrub, so remember that!

The great thing about plastic carboys is that they allow you to see what is going on inside the vessel since they are also see-through, but contrary to what happens to a glass carboy, if you drop one it won’t shatter into a million tiny pieces.

1. Reduced amount of available oxygen: The geometric shape of the neck makes it so that there is much less room for oxygen, which is one of the enemies of beer.
2. Medium durability: being plastic, scratches and intensive use mean that it must be replaced periodically. Plastic is not inert like glass or stainless steel and generally causes bacteria to grow inside of those scratched areas.
3. They can scratch: scratches can harbor microorganisms that can modify the quality of the beer and even contaminate it. Scratches can create biofilms that are very difficult to remove if they persist over time. To avoid this, fermentors should be cleaned with alkaline cleaners at first to remove organic matter, and then with an acidic cleaning solution.
4. The top opening is small: This makes it difficult to physically clean the carboy, like using a brush, and the narrow neck limits the incorporation of hops or spices when dry hopping.
5. They are affordable: Plastic fermenters cost ⅓ of what glass fermenters do and even less than what a stainless steel fermenter costs.

Which one do I recommend?

I believe that the choice between one or the other mainly depends on your level of expertise, how long you think that you will be brewing for, and obviously, your budget:

If you’re just getting into it and don’t know if in a couple of years you’re still going to be brewing, then go with a plastic bucket fermentor since they are extremely cheap and should last you for at least a couple of years.

On the other hand, if you see yourself staying in it for the long run, glass fermentors are going to be your best bet as long as you don’t drop them since they should last you virtually forever, making them actually cheaper in the long run.

Of course, there’s another alternative out there that may be a bit more expensive and not really for beginners, but you may want to look into stainless steel fermentors.

Consider a Stainless Steel Fermenter

The ideal case in terms of quality, shelf life, durability, ease of cleaning, etc., is a stainless steel fermentor since it shares many of the pros of the fermentors on this list without any of the drawbacks, except maybe the price. If you can get a conical stainless steel fermentor, all the better!

Stainless steel fermentors can be cleaned with more products than plastic ones, they last indefinitely, if they break it’s probably because you tried to break them, they have a faucet, and in general, they have a large opening at the top making dry-hopping and cleaning a breeze. Lastly, they are “modifiable”, although in general, I would not recommend it.

The only disadvantage is the price since they can cost 10 to 20 times what a plastic fermentor does.

Conclusion

The use of one type of fermenter or another depends on several factors, ranging from the styles of beer we want to brew, the amount you want to brew in one go, and of course, the price!

However, no matter what fermentor you choose, the truth is that the quality and taste of the beer you brew will mainly depend on other factors, such as using the right ingredients, cleaning and properly sanitizing your equipment & bottles, etc.

So, get the one that better fits your budget and get to brewing!