Always do epoxy before any kind of filler.

 

I personally put 3 coats of epoxy on ALL bare metal before using any filler (or anything else for that matter). If the welds are solid with no holes and the panels were butt welded then there is no need to use the dura glass, simply prime with epoxy and go to filler or high build depending on how good the panels went in for you. If you lap welded the panels then you will need to seal the back side well, but I would epoxy then use a quality seam sealer for that. Just my .02 :thumbup:

Kelly

 

Yep, epoxy before fillers but why the duraglass at all? The MUST for a fiberglass reinforced is a serious myth over welded panels, an "Old husbands myth" if you will.

It does NOTHING for you, other reinforcing repairs over fiberglass, or for over large holes in a "pretend" repair over rust or something like when you have really deep low spot to fill. But for simply over a weld, epoxy, then regular "bondo" over it as good as it gets.

And let me clarify it is NOT water proof anymore than IT doesn't absorb water. It doesn't protect the metal from water, the water will get under it. If you epoxy first, THAT is what is going to protect the metal from rust, what ever you put over it is a mute point once you have the epoxy primer over that metal.

Brian

 

Thanks guys. It is lap welded and in a place where I would need a little fill anyway. I'm using duraglass because at the moment that is what I have the most of and my welds are not near as good as yours!

 

The biggest thing is epoxy first before any fillers to protect the metal, be sure to seam seal the back side or you will have a big cozy home for water and soon rust especially right at the wheel wells.

Also, Brian (Martinsr) done a pretty good job of saying what I was trying to:thumbup:

Kelly

 

you better cure that crap outside with a black bag over it. it will shrink and swell for ever.

 

So it sounds like you guys are not fans of duraglass? I've got some feather rite but it's nearly a year old.

No real good way to get at the back to seal it short of a 1" hole saw... Maybe I'll do that and put a plug in to leave open for winter storage or something.

 

It is not so much the dura-glass we are opposed to, it is the mixing of metal and fiberglass. They have different expansion rates and the seam/joint where the two different materials meet will at the very least begin to show a shadow line after paint. It will usually for a crack between the two different materials and that will lead to water penetration, which leads to rust, and so on.

Add that to the fact that a lot of people read that it is "water proof" and assume you can use it over bare metal, or to fill rust holes, or over rusted metal to "seal the rust in", and do nothing but cause more problems for themselves or the next unfortunate owner.

Kelly

 

It is not so much the dura-glass we are opposed to, it is the mixing of metal and fiberglass. They have different expansion rates and the seam/joint where the two different materials meet will at the very least begin to show a shadow line after paint...

Kelly

So that's what happened! I bonded a fiberglass hood scoop to an aluminum hood last summer and it was perfect but now there is a faint line where the filler meets the metal.

That scoop sees temps from -25 to 240 so this is probably an impossible question but is a there a fix for the filler shadow?

 

I'm sure theres a lot of good info here,from some guys that have done a lot of body work,but I can tell you from an old bodyman that's done radical chops,sections,turned a 4 door '41 Willys into a 2 door Cabriolet,I used a Duraglass skim coat on some bare welds,long before Epoxy was invented and 30+ years later,these cars have no shrinkage,no bumps,perfect like they left my shop in the '80s and '90s,(with Lacquer primer no less) I do use Epoxy now on everything,and usually put my plastic on top,but I still like the way Duragass bonds to ground steel.been working great for 40 years,no need to chage now!

 

I've never had a problem with Duraglass either.
As far as primer before or after filler, it doesn't matter.
The filler will outlast the car either way, if done properly.
To try and protect the metal in case moisture gets past
the filler is a moot point.
If that happens, the filler will fail and you'll be grinding it all
out of there anyway.imp:

 

I've never had a problem with Duraglass either.
As far as primer before or after filler, it doesn't matter.
The filler will outlast the car either way, if done properly.
To try and protect the metal in case moisture gets past
the filler is a moot point.
If that happens, the filler will fail and you'll be grinding it all
out of there anyway.imp:

That is the key, "if done properly."

And there lies the old husbands myth, that if there is a pin hole in the welds or a rust pin hole using a fiberglass product is going to stop it from rusting, and that is simply not true. I have spoke with both Evercoat and USC tech about this. Both made it REAL clear, the fiberglass reinforced fillers are THEMSELVES "water proof" in that if you made a ball of this filler and with it fully cured dropped it into a bucket of water it wouldn't absorb water. HOWEVER, it doesn't "protect the metal" any more than laying a plastic bag over it protects the metal. It will......as long as no moisture gets underneath, because that is all it's doing is "covering up" the metal, not TRULY bonding with it to protect it like epoxy primer does. I can't make this clear enough, this is right out of the tech dept reps mouth, I just spoke with a USC rep on the phone about this a few months ago to clear up this myth with him for a discussion on another forum. It is no different than Evercoats "Everglass" or "Kitty Hair" or "Tiger Hair", they are all simply "covering up" the metal and not bonding with it like Epoxy primer does. And at least with Evercoat (I didn't discuss this with USC) 36 and 40 grit are part of the past as well, they don't recommend anything more than 80 grit for any step using their filler, that is right out of their tech sheet.

So the myth I was referring to is simply that guys think you really are SUPPOSE to put the fiberglass reinforced filler over welded seams and this simply isn't true. Can you, yeah, but it isn't doing a darn thing for you. Weld it properly, and it is a moot point, seam seal the back and it's a moot point, it simply isn't needed nor a good idea frankly, "if done properly". Not that it is bad to use a fiberglass reinforced filler, not at all. But it adds work as it's harder to sand and if the weld seam is done properly it isn't needed.

Brian

 

Most body fillers are polyester based, like boat building fiberglass resin. Polyester resins are hydroscopic, they absorb moisture from the air. If the humidity is above a certain point, the polyester resin base for body fillers will absorb enough moisture to rust the bare steel. Every time the can is opened, it absorbs some more moisture.

I have redone body work I have done in the past, when I was taught to grind with 36 grit, and apply filler to the bare, cleaned metal.
Redoing that body work, there is rust under the filler.

 

I have redone body work I have done in the past, when I was taught to grind with 36 grit, and apply filler to the bare, cleaned metal.
Redoing that body work, there is rust under the filler.

Yep!
And it will stay that way indefinetly.
Long past the life of the car without any problems.

 

LOL never mind! I went through my photos from last year to see if it really was as good as I remember and it's far from it! This is a shot with the first coats of paint on it and you can see the bond clear as a day in it.

I now remember how tired I was of working on it and figured I would clean it up when I paint it now.

 

"Yep!
And it will stay that way indefinetly.
Long past the life of the car without any problems."

Actually, there were some bubbles, or imperfections showing up in the paint, otherwise good paint. I ground a small spot down to metal, and found rust, not a lot, but much more than the small imperfections seemed to indicate.

When I do filler work now, I try to epoxy primer first.

 

Any kind of hood scoop to a metal hood will crack sooner or later. Remember one I put on a kids camaro back in the early 70's. He asked how long it was garuanteed not to crack and I told him all the way to the end of the alley. When you hit the street your on your own.