Minimum hardner to bondo ratio

[brad hays]

I've using some regular bondo to finish something I'm working on and I'd like to mix it so that it cures as slowly as possible. Relative to the recommended ratios what's the smallest amount of hardener you can add and still have it cure?

[Rick Potter]

It's been years, but as far as I know, if it is not too thick and left in the sun a while it will cure without the hardener. I left an almost empty can (yes, can) open outside by mistake, and it hardened.

[Rich Engelhardt]

IIRC, Bondo was a thermoset - meaning it cured by being heated. The hardener just triggered a reaction to generated heat - which in turn aided the cure.
It's been years since I used any, so, this may not be accurate anymore.

And - as Rick mentioned - I bet more than a few of us left an open bucket of it, unconverted, in the sun and ended up with a brick.

[Alex Zeller]

I've heard of people putting it in the fridge or freezer overnight. If it was me and I wanted more working time I would go to an auto parts store that mixes paint. They usually will have a good selection of body fillers. There's better brands than Bondo that come in different curing speeds.