Bondo that wont harden?

If your raw filler sets for a while and needs to be stirred up, take it to the paint store and have them put it on a shaker. Works well and saves alot of problems.

 

i stole this from overspray's link below, and its a good and accurate read.

yes the heat you feel is from the reaction, which is what makes the stuff cure. the temp you work in has a big effect on speed of drying. in summer around here, its not unusuall for it to cure when you are mixing it lol.

i would reccoomend overspray's link to anyone who's lookin for more info.
bondo can be your best freind or worst enemy

skull

 

Hell, all of this time I thought that someone was just using blue hardener it it. Thanks for the info.

 

So... here's a related side-question, using some of the logic in this thread so far:

I bought a can of bondo over the summer but never opened it.

It has sat in my workshop since.

It was 25 degrees all last week (the last thing on my mind was checking my un-opened $10 can of bondo if it was frozen) so should I ***UME that it's ****ed and buy another can in Spring?

 

Try it, it might work fine. I've had bondo sitting around for years in an unheated garage and it has worked fine. What I find that goes bad first is the hardener.

 

I guess I forgot to add. My GF is out of town for the week, so I've been working inside the house, plenty of heat. Just the can sat out in my shop for part of the cold weather, and may or may not have gotten cold.

Got a new can and new hardner, figure its worth a few bucks to just start all over new.
And if anyone wants to show me how to lead on fibergl*** I'll pay for your beers.

 

It was the hardener. Like posted above it loses it's ability to cure the fill. The liquid in the filler is polyester resin. Even if you have some older but clean filler and it seems a bit to stiff to work just add some f'gl*** resin and stir it real good. And yeah, use new hardener. It's not rocket science...

 

Bondo/body filler (polyester/fibergl*** resin) DOES NOT freeze. The hardner will freeze (closer to zero degrees-not 32) and can be compromised so it will not work. Keep the hardner inside, don't worry about the bondo freezing. It will need to be warmed up to room temperature before adding the hardner, and if the can has been sitting for a while a trip to the paint shaker is much easier than stirring it.

overspray

 

Cold Temperature, and not enough hardener. Thats my take on it....

 

I never had it freeze. I puttied up an old pickup one winter out in the shed 0-15 below and the bondo wasn't frozen. I could mix it up but it would not harden until I warmed it. I used a propane torch because I didn't have a heat lamp and you don't want to get it too hot or it will burn out the resin. It also flashed over when I first hit it with the flame because of the solvents in it.
The hardening process is called polymerization. fire is also polymerization. Rapid polymerization is the technical term for an explosion.
just like wood doesn't spontaneously burn/polymerize in air, the bondo doesn't spontaneously polymerize from the peroxide in the hardener. there has to be enough initial heat to start the chemical reaction.
That's why it will sit there with the hardener mixed in and never harden until the temperature rises.
They came up with some other pre-mix concoctions for manufacturing where the hardener is already mixed in with the resin for the proper ratio but also with a retarder so it doesn't harden until they want it to.
They put a chunk of the putty in a heated mold and it forms up hard right there in seconds.
There's also a pre-mix that's set to harden with UV light
pretty amazing stuff but like the other guy said if it didn't set right as expected gouge it out and start over.
Maybe they came up with some water based stuff I don't know about but back in the bodyshop days I never had a problem with it freezing just not setting unless if wasn't warm enough

 

You sure you didn't grab the plumer's puttyby mistake, or maybe someone is messing with you and chaged the contents!

 

You haven't had it in a cold enough climate It was below -40 here last week and I can tell you the samples I had in my trunk were frozen solid. It worked fine once unthawed but it was definitley frozen.

And to the original poster please DO NOT add 3 times the amount of hardener as suggested else where. Almost all filler issues are catalyst issues and adding that much extra hardener is going to lead to a whole host of other problems.