Body Filler over Paint ?????

SMYDA

Knuckle Dragger
Joined
Mar 25, 2008
Messages
508
Location
Arizona
Body Filler over Paint ..... that is the question?

"YES" ..... "NO" ..... Why? If so When?

I'm curious to the forum members opinion (or understanding) on this.
 
If you mean apply body filler over slick smooth paint, then no. don't do it. If you mean apply body filler to a properly prepped panel that is already painted then yes. by properly prepped I mean sanded so that the filler has something to hold onto (bite). Usually somewhere in the area of 220 or rougher grit. the filler should not contact anything that has not been prepped for it. it if does it will simpy pop or sluff off. Technically you should sand an area about three times bigger than the damaged area to be repaired with body filler. That is so that it can be properly blended back to the level of the origional finish. Then after it is fixed and primed it will not show a line when paint is applied to the panel that has been filled.
 
Best bite for bondo is around 36 grit, so simply if you do that the paint is gone anyway. :bounce:
Then there's all the solvent, cure and moisture problems.

All kinds of new stuff out there, on mine, I wouldn't do it, on yours, maybe, if I was in a rush. :goodevil:
 
I wouldn't if I could avoid it. I'd be worried about the solvents in the filler lifting the paint or vice versa. Also, it would be impossible to know what's under the paint. If the paint lifted because of poor surface prep, then the filler would lift with it.
 
I tossed the question out of curiosity.... to see what the general thinking
is on the topic.

When I first got into paint & body work in my teens (early 80s) I was always
told never bondo over paint ... that's "butcher work". Logic would tell you that
back in those days most everything was still painted with Lacquer based
products. How many of you stripped your car with a razor blade? Certainly
wouldn't want to put filler over that and for good reason.

Well technology has changed since those days. About 8 years ago while I was
working for a BMW / Porsche Dealer body shop the Reps for "Evercoat" paid us
a visit (on a couple of occasions) and basically held a class on how they wanted
their product used. Up and to this point we were still grinding all repair areas to
bare metal before applying filler. Also keep in mind we rarely worked on anything
over 10 years old.

The "Evercoat" Reps said to sand the painted surface with 80 grit and apply the
filler. ONLY remove paint to bare metal when welding or a stud gun needs to
be used and only in that exact area.
The reason for this is that you do not want to remove any of the factory E-coats
and compromise the original corrosion protection.
This is for an OEM painted surface. If the car has been repainted and you do
not know the products used or quality of work then it is recommended that
NON-ORIGINAL topcoat be removed.

From that day I started doing it their way. It did make my life easier and I
was able to keep the repair areas smaller which in turn made life easier on
our paint crew. When I started working for my current employer (5 years ago)
they were still doing things the "old way". They soon changed. In this time
I have not known of either shop having a repair failure do to this method
using "Evercoat" products.

Anything built Pre 1990 I would say stick with the old method to be safe.
But if your working on anything late model stop grinding that E-Coat. :thumbs:
 
I have a couple of spots on the '72 where the body work is need filled, have some Bondo Y spot putty in a toothpaste tube...I suppose to scrape out the paint and spread it over good....

but then the question is....does it need a great automotive primer? or can I escape with just applying Rustoleum semi gloss black over it??

there is cheep rattle can flat on it now, over the last year or so....

:surrender:
 
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