oklahomajewel wrote:If I have some already hardening up in the scoop, and set it aside for a while to finish hardening then throw it away , is that dangerous?
Nope. Bondo getting so hot when it sets that it catches fire is really only a theoretical risk - I've never seen anyone get close to it - unlike with polyester resin which is quite easy to get smoking, if not actually on fire.
Nevertheless, it is sensible to allow unused Bondo to set before throwing it in the trash. If you time it right, you'll feel it get at least as warm as your skin - which is hardly a fire risk!