a mystery! I've recently been canning pears by packing
them fresh in hot jars and then pouring hot syrup over
them. However, when I processed the jars in a hot water
bath, some of the jars exploded and I lost the fruit.
Others never sealed. I've used the same procedure with
apricots and this never happens. Please do some sleuthing
next time you are preserving pears, simmer them gently
in syrup for five minutes before putting them in the
canning jars. This is called a "hot pack" method, and
is useful for pears because, like apples, they contain
an abundant amount of air.
Cooking them lightly before packing them in jars allows
their tissues to soften slightly first so the air can
more easily escape. Then during processing, there's not
so much pressure exerted when air bubbles are released
into the limited space of a canning jar. This doesn't
happen with apricots because, like many other fruits,
they contain less air than pears and apples.
Here are a couple of other considerations too: We're not
sure what type of bottles you're using but "jars breaking"
during processing raises the point that it's best to use
jars designed by preserving companies. They are made of
thicker glass than many other types of commercial jars,
and they can withstand the high temperatures of a boiling-water
bath, so they're less likely to break during processing.
Also make sure you allow some space between the fruit/syrup
and the jar lid by NOT packing the fruit right up to the
top. This space is called "head space" and it allows room
for the fruit to expand during processing. Usually this
is 1/2 inch (1 cm), but note that the recommended head
space differs for various foods. You can find this out
(and lots of other hints too) by purchasing an up-to-date
preserving book, usually available in the preserving section
of local supermarkets or check the Web sites of companies
that make canning supplies such as Bernardin's (www.homecanning.com).