watercolor question

A fellow artist emailed me asking what she should use to seal her watercolor postcards so that don't get ruined in the mail.

An excellent question!

But let me start by saying I'm pretty comfortable with the inherent risk of mailing "naked" art through the mail.  Sometimes the elements and postal machinery interact with our work.  For me, that's all part of this big mail-art adventure.

But it's true that if your mail carrier delivers in a downpour, your watercolors are more likely to be effected by the weather than other types of art we swap here.

SO....
have any of you sealed or protected your watercolors, and if so, what did you use?

When I have something I don't want to smudge or smear, I use Krylon low-odor clear finish.  It comes in an aerosol can like spray paint and is readily available at your average craft store.  But even the low-odor variety is pretty nasty and should really be sprayed outside or in very well ventilated space.

Have you used anything different?
I welcome your thoughts and advice for sealing watercolors
(even if you decide NOT to seal these pieces)