Colin Campbell writes:

I saw a friend riding the other day, and we were discussing what to
carry on a ride.

He mentioned, "A patch kit, and two tubes of glue. One that hasn't
been opened, ..."

And I jumped in, "...and one that has dried out since it was used
for the last repair."

Don't rely on the unopened tube of glue to be any better at no
evaporating. Until the tire patch makers learn that a crimped tube
leaks, we will continue to see completely dry unopened glue tubes.
Plastic screw caps with a metal/cardboard insert seal better than a
poorly crimped tube. Unfortunately, many of them are poorly crimped.

To test this, open a tube with its threaded end up and see how much of
the tube can be flattened before glue appears. Just the same, a well
crimped tube contains clear liquid, not milky jell, as many specimens
do.

We laughed, and went on our way. But how does anyone keep the
darned tube from drying out (or actually evaporating, I guess)
between flat repairs?

And where can one buy extra tubes of vulcanizing fluid?

Any good bicycle shop will do.

Jobst Brandt