working with bondo

has anyone thinned bondo with a solvent

and with what solvent?

What’s the application? I’ve never heard of that being done.

I know Bondo also makes a Glazing/Spot putty that’s a lot thinner and “lightweight” than the full on Bondo body filler. You might want to try that.

the application is building up the form of a sculpture.

The Bondo Spot/Glazing putty is great for surface finish of a model, as you can put it on really thin to fix small imperfections. Plus you don’t have to spend time mixing the stuff…

However, if you are building up a form, you would probably want to use the regular stuff. It all depends on your application, and what you want it to do.

It is hard to know what to tell you without knowing the specific purpose…

you can thin bondo with polyester resin.
bondo is polyester resin with fillers to make it like a putty.

you can even go the other way and thicken the resin with bondo.

places like napa sell products that are pre thinned like Jackal said called spot putty,

but its easier i find to just get a bucket of the thick stuff and a can of polyeter resin at the same time, and mix to your hearts delight.

i would make sure and test your mixtures with the hardener to make sure your not using to much or too little before you work on your part though.

you can thin bondo with acetone. before you add the hardener.

wow, that is interesting… in regards to the bondo+polyester resin.

i am curious what your application was.

i was at home depot today and realized there is bondo body filler as well as bondo glass reinforced.

i was not familiar with that and am thinking you all are referencing the bondo body filler. yes/no

it seems best to build the filler up in thinner layers but say i wanted to just dump a whole bunch in a form or mold… does it crack if there is too much mixed at once.

And if so it seems like the glass filled might be awesome for fixing that.

Be careful about how much you mix at once. The hardener and bondo, when mixed, create a chemical reaction that generates HEAT. I’ve witnessed extreme cases where it will get so HOT it will smolder.

When spread out in thin amounts you can still feel some warmth. But a container filled with bondo can’t release the heat fast enough.


Using a materail like a “glazing putty” is far superior to trying to consistently mix your own “thinner” bondo. It’s superior (IMO) because you do not have to stop and mess with it. Another consideration is the reliability of the mix … nothing pisses me off more than when a material fails to kick off, and I have spend an hour digging out and re-doing it.

Here are two companies that supply a wide range of materials that I use.

Evercoat Company

Evercoat provides a description of what each of it’s products; helpful in selecting for a particular application. Once you know what it is you “need” any other manufacture’s material(s) are understandable.

Product Directory


“Glazing Putty” ( a “thinner” material for filling heavy sanding scatches; not intended for filling large depressions).

“Specialty Reinforced Fillers”

Also see:

TAP Plastics