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Glass vs. Plastic Carboys - Which Is Better?

Why You Should Care | Comparison Chart
Logical Arguments and Explanations | Conclusion

Does It Really Make A Difference?
There seems to be a lot of debate among home winemakers these days about the type of carboy that should be used during fermentation and aging. Are glass carboys better than plastic ones? Or is it just the opposite? Most importantly, does it really matter?

Yes, there IS a difference - and grapestompers.com hopes to illustrate why there is a clear choice when it comes to selecting the type of carboy to use.

When all the evidence is weighed (see below), the choice appears to be obvious. Despite this evidence, the selection of one type of carboy over another may have little to do with the facts; for many winemakers, it simply boils down to a matter of preference.

Comparison Chart
Use the chart below to see (in bulleted format) the advantages and disadvantages of glass versus plastic carboys:

Type

Advantages

Disadvantages

Glass carboy

  • You can see what's happening during fermentation and clearing.
  • Glass is easier to clean and sanitize than plastic
  • Glass is impervious to scratching during normal cleaning routine.
  • Easier to get a good airlock seal.
  • Glass is inert; no chemicals or solvents to leach out.
  • Little or no oxidation occurs to wine during long term storage.
  • Glass is breakable, and thus more dangerous to handle (slippery when wet).
  • Glass is heavier than plastic.
  • Sunlight through clear glass can harm wine.

Plastic carboy

  • Plastic carboys may be cheaper to purchase than glass carboys.
  • Safer to handle and lightweight. If dropped, there's no broken glass!
  • More difficult to monitor wine during fermentation and clearing.
  • Very easy to scratch surface while cleaning; even microscopic scratches can harbor bacteria that will ruin your wine.
  • Plastic is much more apt to harbor off tastes, odors, etc.
  • Plastic carboys may tend to make wine more difficult to clear
  • More difficult to get a good airtight seal
  • Oxygen diffusion across barrier more likely during long term storage. Can you say vinegar?
  • Depending upon the source, plastic carboys may leach solvents when filled with acidic or alcoholic fluids.
  • When full carboys are lifted, the bottom may deform (pooch out) and draw in the water from the airlock.

Explanations
It's simple - Glass is easier to clean and keep clean than plastic. And, because it's clear, it's easy to see if there is any film or gunk on the inside of the carboy. Plastic is easier to scratch during the cleaning process, and in these microscopic cuts or gouges, harmful bacteria and other nasties can hide, waiting to pounce on your next batch of wine and ruin it. Even if not scratched, plastic contains microscopic pores that can harbor the same harmful elements.

Ask any amateur winemaker... the number one reason why wine "goes south" is a lack of proper sanitation. Having a carboy made of glass is your best insurance against this common problem, since it is so easy to clean.

Glass is not porous to oxygen like plastic. In the scenario of bulk aging wine in a plastic carboy, you'd really want to keep a close eye on the oxygen levels.... we've all heard stories of wine turning to vinegar because so much O2 was able to diffuse across the plastic barrier!

Glass does not harbor "off" odors and tastes like plastic can. Try this experiment: put something smelly (like anchovies or sardines) in a sealed Rubbermaid or food grade plastic container, and also put a portion in a covered glass dish. After a period of time (week to a month, which would simulate aging in a carboy), remove the smelly stuff and wash each container as well as possible. Despite repeated washings, you'll still be able to smell the remnants of the substance in and around the plastic container, but not in the case of the glass dish or bowl. Imagine accidentally imparting an off odor like that to your wine because you used a plastic carboy!

Conclusion
Even though plastic carboys are safer to handle and won't break, we believe that the advantages of glass - most notably those that ensure your wine won't be tainted - are more than enough to convince even the most vocal proponents of plastic carboys.

This is why grapestompers.com recommends (and sells only) glass carboys for
fermentation and bulk aging.