Expert: Brandon Sievers - 9/25/2006

Question
Hello, I'm needing to fill some minor pits in my bondo. I used a Fiberglass resin painted over and then sanded but they are still there. I would like
to skim coat with thinned out bondo or something like that. Is this possible? The bondo I'm using is to thick to skim coat with. I've made Saddlebags for my Mororcycle out of Fiberglass and bondo. I would just like them a little smoother then what they are right now. Also I shot on some Primer and it's pretty smooth. When I've worked with Primer in the past it was bumpy
and then you sanded smooth. Should primer shoot on smooth?

Answer
first, even thick bondo can be thinned out. Take a given amount of bondo and add hardner, a little less than usuall. Then add a table spoon or more of fiberglass resin. if working with a large amount of bondo and then add a little more. Add a few drops of the resin hardner and mix it up. It will thin it right out.
As far as smooth primer, it depends on what primer it is. If it is a high build primer it will be more textured than an epoxy primer that goes on very thin. You may need to turn down the air pressure in the gun. Make sure that you use at least a 1.4 tip for your primer gun. A tip that is small clogs easily and will add texture. After the primer is applied, spatter on a dark paint to use as a guide coat. When you wet sand it the dark paint will diassapear. If there are low spots, then the dark paint will not be touched in those areas because the block stays true to the surface. Hope this helps.