"Wing" wrote in message ...

Just read an idea couple of days ago somewhere.
The suggestion was to gently place a metal rod (as thick as will fit
through the neck and carefully guided past the plants) into the flask until
it touches the centre base opposite the neck, wrap flask in newspaper or
towel, then tap the other end of rod with hammer. This should knock the base
out.

A lot of the time it doesn't just cleanly break out the bottom, but
even if it breaks unevenly, it'll be a lot cleaner than using a
hammer, and you're much less likely hurt yourself or the plants on
lots of little tiny shards of glass. Personally, I use a long (~12")
cheap screwdriver.

Michael