From the HBD Archive
From: Pete Soper <soper@maxzilla.encore.com>
Subject: headspace
Date: 1989-10-26 14:18:56 GMT

Unless you know what you are doing, do not try to use 1/8 inch
of headspace. The reason is that thermal expansion can cause the
1/8 to turn to zero and the expanding beer will eventually break
the bottle. You would think the cap would be pushed off, but it
never is - the glass is the weak link. I have purposely tried
extremely small amounts of headspace and can vouch for the
tradeoffs.
For instance, bottling your beer while it is cold, then having
the bottles warm up to room temperature can cause significant
expansion and you must take this into account. Likewise, bottling
near room temperature but letting the bottles get into a hot
environment may also bring expansion into the picture and cause
problems.

I've settled on a starting value of 1/2 inch for headspace to
leave myself some margin for error.

As for the advantages of reduced headspace, here are the ones
I've observed:

1. There is more beer in the bottle.
2. The beer stays fresh longer.
3. If a bottle does turn out to have a flaw and it breaks, it just
cracks and drains. There is no explosion.

Speaking of bottling, sometimes you can arrange for the headspace
to be filled with foam when the bottle is filled and thus start out
with mostly C02 instead of air in the headspace. This is harder to
pull off with larger headspaces.

--Pete Soper

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