The Stovebolt Site Forums The Shop Area Paint and Body Shop Another bondo question

I have been reading topics about applying bondo and it appears that the recommended practice is to epoxy prime bare metal before applying the mud.
Is that correct? Back in my day (light years ago), bondo was applied directly to the ground, bare sheetmetal for best adhesion. I'm gearing up to begin the body work on my '67 C20 and am interested in the latest bodywork techniques.

Thanks in advance

CrashBob

That's a good question.

You can usually help yourself if you hit the "search" button on your topic of interest to see if previous discussions have already taken place. Then you don't have to wait around for people to answer.

Here is a previous thread that seems to fit your question. I found it doing a search on "applying bondo".

http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=4;t=003164#000006

It should get you started until some other people can address your question.

Thanks Randy,
I'm not real swift about using the handy features on forums. I appreciate the tip.

Epoxy primer is the only one that you can put polyester body filler over. This will seal porous welds or other repair areas from moisture which is the worse enemy of filler. If metal is solid behind filler then use 36-40 grit on bare metal then apply filler; if metal is too smooth filler will not stick.

This topic has come up several times - it is always good fuel for debate, so we haven't resolved the issue yet. The consensus seems to be that it should be applied to bare metal. Incidentially, that is how I was taught, and I've enjoyed good results.

So.. I just got to ask.. If a person is using eching primer and is planning on using filler right on top of that eching primer.. What filler should one use? Everyone has told me to put it over bare metal as well but as I do a little at a time it would make sense to me to just lay it on the primer... Or should I spray some other type of primer there and apply the filler? I am really hung up on putting the filler on the primer. It seems I see a lot of rust under old filler and thinking that some form of sealer would help. Sorry to ask, I read the posts I am just more confused.

Don't use filler over self ething primer it won't stick for long. Contact the body filler manufactor and you will find out that bare metal or eproxy primer are the only surfaces it will srick to for any length of time.

Put Your filler over bare metal, as long as
there is no chance of water getting to the back of
it....if You etch the metal with metal-prep to seal the metal....then put Your filler on when the
metal feels dry to the touch...and don't go real thick with Your filler.....Also remember this....
The more hardener You put into the filler, the
less gripping power it will have...BB

What ever you do do NOT apply filler over etch type products. The acids in the etch wil react with bernzoxide in the filler's hardner and will cause problems with adhesion.

If you have etch on metal remove it where the filler goes.

ONLY and ONLY can epoxy primer be used with filler. If you want filler on top of primer then epoxy primer is your only choice.

Personally I apply filler over epoxy vs bare metal. Even many top car manufactors have stated that in order for the car to retain its factory warrenty that epoxy must be applied prior to body filler...Eric

I bought a lead kit from Eastwood recently and it came with a video that covered both using lead and using plastic filler with no prejudice towards either. The older fellow giving the filler advice really knows his stuff and offers several good tips. I'm sure they sell the video seperately so for a few bucks it's a good read. At our shop the guys usually use epoxy primer but always do if there's any chance moisture can migrate from the rear side, like at molding or trim holes. The man from Eastwood went to bare metal after roughing with 24 grit and said to push really hard when applying the first coat of filler.