North American Fruit Explorers mailing list at ibiblio

[nottke <nottke1@earthlink.net>]

Del,
In my experience, if the center pops down upon cooling, there is enough
vacuum to seal the canning jar lid's plastisol sealant until you desire to
open it, as long as you are using new lids that have been heated.  If you
want a tighter seal, you can leave a little more headspace, which upon
cooling to room temperature, will give a stronger vacuum.  I am a chemist
and my wife is a food technologist, both long retired - we both spent a few
years at the American Can Company in food container research before they
became a bank and we moved on to other companies.  Our procedure is to have
the lids, plastisol-side-down in a sauce pan of gently boiling water on the
back of the stove.  The sterilized jars, containing two tablespoons of hot
water, are placed in the over-the-stove microwave and heated for about 5
minutes, which boils the water and steam-heats the jars to their tops.  My
wife plucks a jar from the microwave with jar tongs, fills it with whatever
we are canning, which is usually close to boiling, but not always.  My wife
uses a tongs to dip a small piece of sponge into the boiling water and wipe
the rim of the jar.  She has a plastic wand with a magnet on the end that
she uses to pick up a lid out of the boiling water and place it on the jar.
Then comes my part - placing a screw-down rim over the lid and screwing it
on tight, holding both jar and lid with rubber-lined pads.  The jar is then
placed upside down for about 5 minutes, and the screw-down rims are not
removed until the next day.
In the last nine years we have had one jar lose its vacuum on storage - my
wife attributed it to a defect on the rim of the canning jar, it had one
spot on the rim that was a little high.
Particularly with widemouth canning jars, I can often pry the lid off with
my thumbs, but the contents have always been fine.

Jim in central NC .... hate to tell you that it was 71F here today and I
took photos of two butterflies that wandered by.
===========
>My wife has had a Finnish steam juicer for 20+ years but quit using the
>method you describe because it never got 100% seal for her - lids could be
>much more easily pried off than if it were hot processed. Even though all
>the lids looked like they sealed (center down) to double check the process -
>all came off very easily with a little thumb pressure - which made her
>question the integrity of the seal. Any comments?
>Del, N. MN. ......a crisp -10F this AM with the biggest brightest sun-dogs I
>have ever seen