Body filler (NOT fiber glass) the other kind

I'm using body filler to smooth out a few welds. Yea, it's a show thing, but I figured I'd try it. When I apply primer, will the primer soak into the filler? So, is there something I need to apply to those areas before I apply primer and paint? The directions didn't mention any.

Guess I should have asked this BEFORE I started. duh

 

Paint can go straight over primer or use a sealer then paint.

 

So, primer soaking into the filler is a none issue?

 

Never had a problem with it soaking in, usually does. Maybe add a few more coats of primer on the filler to fill it, and then your paint won't tend to do the same thing. Another thing is, I usually put a top coat of finishing filler over the regular filler, and it seals it.. Evercoat Glazing filler I think is the name.

 

I tend to use primer, then a gloss top coat to seal it. Then primer before the final paint.

 

I don't know that primer soaks in, but some do indeed shrink and pull into sanding scratches over time.
You can prime it today, look at it in 2hrs and it'll be fine. 2 weeks or 2 months from now it will show every
sanding scratch because as it cured it shrunk and got pulled down into the scratches. In severe cases it might even crack.

 

Yes it does soak in a bit for sure. You need to prime and sand these spots several times until you no longer "see" the edge of the primer where it feathers to metal. Or when you paint your topcoat you will see every spot you applied plastic filler. Good urethane high build primer can do it in 2 coats and epoxy primers need around 3 coats to achieve full plastic filler hiding. This will also reduce "sand scratch swelling" which is where 3 months down the road you begin to see the sand paper sctatches in every spot you applied plastic filler. Make sure your filler is sanded down to at least 220 to also help avoid this. Do not leave 60 or 80 grit scratches and then flog the high build primer over it. Those scratches will come back to haunt you for sure.

 

Thanks for the tips, guys. The primer didn't soak into the filler and everything looks great.

 

If you are working from bare metal I would use epoxy primer then work up from there.

 

Let it cure very well, the bondo and the primer, before top coating. It will shrink when it is exposed to sunlight and fully cures. I would take it down to 320 or 400, a step at a time with a d.a. or change directions sanding each grit change from 36 or 80, depending on the application, before primer, then synthetic sealer, then top coat. Best to apply bondo direct to metal with 80 grit grooves to give it teeth. Best of luck!