Tonight a few seconds after lowering the last quart jar into
the canner I heard the muffled thump that signals you've
just lost a jar. I quickly pulled the jar back out in a vain attempt
to save it, of course, the bottom had cracked neatly off and the
entire quart of applesauce went slithering into the canning water.

Damn damn damn!

Later the post mortem showed the bottom of the jar looked
very worn with a lot of gouges, like someone had been sliding
the thing back and forth over a long bar. Of course, this was
one of the used ones that I picked up from the thrift store.
Obviously one of those scratches was deep enough to create
a weakness and when the hot water in the canner hit it, the
sudden expansion caused the flaw to trigger the crack.

So, just a reminder warning, if you buy jars used as I do,
aside from the run the finger along the rim trick, carefully inspect
the jar for scratches. Faults and occlusions that exist in the glass and
were there when the jar came from the factory are fine - I've
canned in 90 year old jars that are full of bubbles, pits and
all manner of dimples and warts, no problem. What you have to
look for is scratches in the glass that were made after the jar left the
factory. I'm going to really keep a close lookout for those from
now on.

Ted