From the HBD Archive
From: "1107-CD&I/VIRUS DISEASES" <henchal@wrair.ARPA>
Subject: hermal shock/glass carboys
Date: 1989-02-23 20:00:00 GMT

Jeff Miller writes:

"After blowing up a second glass fermenter with thermal shock I
broke down and went to my homebrew supplier to get a plastic

I am a little curious about the method you were using to
require the addition of very hot liquids (I am speculating) to
the carboy, as well as the result. I have been brewing almost
exclusively in glass, non-pyrex, carboys (5.5 to 7.5 gal) for
awhile. Were your carboys old and well used (no doubt) ? Are
carboys more likely to break when they get older (probably) ? Do
my assumptions apply in your case?

My laboratory experience has taught me that glass vessels
break on rapid heating and cooling. If you have to add hot
liquids to a cool carboy, start with only a small amount of the
liquid...allow the carboy vessel to adjust to the changing
temperature conditions slowly. This practice is usually
applicable with all but the oldest of glass vessels.

When I brew, I always cool my wort with a homemade copper (1/2
inch diameter by 30 feet coil) wort cooler prior to addition to
the carboy. The only time that I add super hot water to a carboy
is if I pre-boil my brewing water before use. Generally, I have
abandoned that practice since I got a 30 qt brew kettle and and
boil the entire wort (5.5 to 6 gal) at one time. (By the way
nice 30 qt brew kettles are available cheap from Great
Fermentations for about $30. Well worth the price.)

Erik A. Henchal, Ph.D.

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