From the HBD Archive
From: Darryl Richman <>
Subject: Brewing in plastic
Date: 1989-03-13 15:23:55 GMT

Shall we bring up a religious war again? No? Oh, come on, it'll be fun!

My practice has been to do two stage fermentations in the polycarbonate
plastic 5 gallon carboys that my local water company delivers in. As far
as I can tell, there are three reasons to prefer glass over plastic: 1) glass
doesn't scratch easily, 2) the glass walls don't flex when you pick up the
carboy (and thereby threaten to suck the sterilant out of the airlock and
into your beer), and 3) glass is rather less permeable by oxygen.

But... I did a brew demo down at the shop where they only have glass
carboys, and I busted one. I was doing something that I regularly do
with the plastic carboys: rocking them back and forth to knock down the
foam head on the just pitched wort. This is a real no-no with glass. Glass
is very fragile. I have actually bounced a full plastic carboy (from about
a foot up).

Glass is also easily subject to thermal shock. I regularly boil 5 gallons
of water for rinse and sterile purposes and pour the water directly into
a plastic carboy, which I then cap. By the time it is cool, it's in a safe
place, out of harms way. (BTW, someone asked about Pyrex carboys: you can
obtain them new from the Student Science Service in Burbank, CA. A year
old catalog lists a 5 gallon one at $125.)

The polycarbonate carboys don't scratch easily, and if I were to actually
damage the surface of one, I would trade it back to my water company. (They
have the same problems and can recycle them.) They may eventually breathe
some air, but during fermentation there is an overpressure inside and so
CO2 would tend to get forced out, not O2 in. The plastic carboys are, of
course, *much* easier on your back.

I'm still working on #2 above. I usually grab the little floating cap out
of the airlock and put a blow-by tube (sterilized) onto the lock while I
move it. It's a bit clumsy.

--Darryl Richman

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