Car Body Filler

[Hermes2020]

I have a technical question on using car body fillers. I am referring to the type that is a putty that is hardened with a catalyst. My question is whether anyone here knows whether it will be safe to paint over hardened body filler with artist's oil paints. My guess is that it would be better to prime it with a gesso coat first. Any comments or suggestions would be appreciated.

 

[snoball]

I would do a test run of both methods before working on your actual piece. There may be a chemical in the bondo that would keep oil from drying.

 

[Hermes2020]

I would do a test run of both methods before working on your actual piece. There may be a chemical in the bondo that would keep oil from drying.

Yes, thank you that is definitely something I will do.

 

[Artyczar]

I have restored cars and have used this Bondo putty before. After you sand it smooth, the primer that's used before you paint the car, which IS oil-based, is a gray primer, but I don't believe that is water-based. Bongo once spoke of it to use as a "gesso" under paintings for a cheaper alternative. You can buy it at the hardware store in a spray can. To be safe, I'd use that instead of an artist material gesso, which will probably be water-based.

However, now that I think of it....The Bondo putty might withstand water. When doing body work on a car, one is usually first removing the old coat of paint, which requires wet sanding. Then you hammer out the bulk of the dents, then use the Bondo to smooth out the remainder, then prime, then paint. Maybe this helps?

 

[Hermes2020]

I have restored cars and have used this Bondo putty before. After you sand it smooth, the primer that's used before you paint the car, which IS oil-based, is a gray primer, but I don't believe that is water-based. Bongo once spoke of it to use as a "gesso" under paintings for a cheaper alternative. You can buy it at the hardware store in a spray can. To be safe, I'd use that instead of an artist material gesso, which will probably be water-based.

However, now that I think of it....The Bondo putty might withstand water. When doing body work on a car, one is usually first removing the old coat of paint, which requires wet sanding. Then you hammer out the bulk of the dents, then use the Bondo to smooth out the remainder, then prime, then paint. Maybe this helps?

Oh yes, thanks, it gives me a starting point. I am thinking of using it to take an impression of a rusty old crankshaft and then to incorporate the resulting cast into a painting. It will create some nicely shaped holes that will be a sort of macro texture. It probably sounds a bit batty, but I think it can work.

 

[Cremnitz]

I think Bondo / body putty is basically thick epoxy with fillers in it to make it lighter and easier to work with on the car. I have seen some very old Bondo. like 50 years old an a rough looking 64 Corvette - that was exposed to the elements because the primer and top coat had flaked a way, and it had broken down and was crumbling / cracking / falling apart. On the other side of that coin, if it is protected from UV light and extreme weather, my guess is it will last forever. I just recently sanded into some 17 year old body putty on a pickup truck that had been exposed to summer winter fall and spring weather for 17 years, and it was pristine, underneath the intact vehicles top coat.

 

[Hermes2020]

Thanks Cremnitz. I've been having second thoughts about using car filler and will research some alternatives.