body filler

[born4ford]

I just got my doors back from the sandblaster. They did a great job getting all the adhesive gunk and paint off. I put a coat of self etch primer on and now I need to weld up the old RV mirror holes but otherwise there are just some very minor dings here and there, nothing over 1/8". What brand and type filler would be best to use? After spending 8 hours working on 3 busted off bolts (the first on this 50 yr old truck) I would like something that goes on smooth and sands easily.

Julie

[LM14]

I would not put any filler over etch primer. It needs to be totally removed since it is so "hot". Over epoxy is fine if it has some mechanical tooth (roughed up) or is still within the mechanical bond time period.

I prefer Rage Gold or a similar fille.

SPark

[born4ford]

The combination of primers and fillers id way more complicated than I thought. I just did some research thanks to the advice of LM14. Seems like self etching primer can really complicate things. Would it work to put down a layer of urethane primer, scuff it up and then do filler?

I'm thinking that in the future I should use an epoxy primer (DTM) over the bare metal because it looks like you can do the filler right over that.

Julie

[LM14]

I go straight to epoxy primmer on stuff to seal it all up when it's clean. Every brand of primer is different for the chemical adhesion time so this is a good time to sit down and do some research and actually read the company instructions. It can make a huge difference.

Every body man you ask will have a different opinion on mud over primer, what primer to use, what brand to use, etc. I don't think there is an ultimate "right" answer. It's done so many different ways, and most are successful, I think it depends on the skill of the person and finding what woks best for you.

For me, I like to do hammer/dolly work on bare metal just back from the media blaster (my latest favorite chosen method if paint removal), scuff/sand it then give it a couple good coats of epoxy primer. To put the epoxy down on freshly cleaned metal by using plastic media blasted steel (my choice of paint removal media) you have to scuff/sand the panels to get a good mechanical adhesion. The metal is too smooth for the paint to stick at that point. I usually use a DA on large areas and scotch brite on small areas.

I have used etch primer in the past and not had any problems. I do not put plastic filler over etch primer. Etch primer gasses off for a long time and it can lift putty. If you want to put mud over etch primer, I would sand off as much as possible and go for a mechanical bond and try to get that primer out from under the putty.

I know guys that etch, epoxy, body work, polyester, high build and paint. I know guys that epoxy, putty, high build and paint. I know guys that putty, high build and paint. There is a good build thread on here that was a high end restoration job and he let you follow along with every step of body prep.

viewtopic.php?f=32&t=30924

Read everything you can find ant try to educate yourself. Find out what you are comfortable with.

Good luck,
SPark

[grump]

Go to Autobodystore.com/forum. They have a lot of info on this site. There are novices to professionals on this site. There is a thread for body filler that has a link to a article on the use of body filler that is very informative. I use Rage by Evercoat. The Rage Ultra is getting really good reviews, it is a bit pricey but very easy to use.

[topstring]

I work for a shop and we just tried the new Evercoat Rage. It sands easier than any filler I've used (in my opinion)..downside is it is 40-50 per gallon!

[jamesdfo]

Seems like these days, most of what you see is filler over primer, BUT, most body fillers are POLYESTER Resin based, and Epoxy is....EPOXY. So I would like to have someone who has more of a chemical background than I explain to me CHEMICAL ADHESION between the two products??.......or, to be safe, after an appropriate cure time, you could just scuff the epoxy with some 80g paper, blow it down real good, then work your filler in real , real good, and know that you have MECHANICAL ADHESION working in your favour:)

James

[LM14]

I have 4 different friends that own body shops. All 4 gave me different answers, James. I'm no chemist but I had the same question, here's what I learned from them.

What most seemed to agree on was no filler directly over etch primer unless it's at least a year old (or baked) so you are completely sure it's gassed out. Only 1 puts any filler directly over etch primer. They suggested if you use etch primer, use it to protect the area but scuff it back of for filler work. Most skipped etch primer completely and went straight to epoxy primer because of this issue.

They split thoughts on filler over epoxy primers. They all agreed you would be better of scuffing your epoxy primer before filling if you were unsure on the age of the epoxy or filling over bare metal. Some filled over new epoxy and others scuffed it. The mechanical window for a bond is anywhere from 48 hours to 2 weeks depending on brands involved. A scuff would make me feel safer.

All I really found out was that there are no clear cut answers from anyone I've talked with. Most did mention to follow the directions on the filler and ignore their personal opinions. Out of the 4 shops they prefer 3 different fillers so maybe that explains some of the difference of opinions.

Seem that what works for one guy is considered the worst thing you can do according to the next guy. They all used their favorite stuff and stuck with it and repeated the same process that worked for them in the past.

Good luck,
SPark

[jamesdfo]

Steve: I am a journeyman A/B Mechanic, spent 10+ years at it, but have been out of the trade for a loooong time. I was using epoxy primer, high solids primer, and two component spot putty even back in my days. BUT, when I did my apprenticeship, it was strictly verboten (by trade school instructors, and also by my employers) to apply filler over paint.....
SO, much later, (possibly early 90's??), I started seeing articles in Hot Rod/Street Rod magazines where they were applying body filler over epoxy. The rationale being the epoxy creates a moisture barrier between the metal & the filler (because the prime ingredient of body filler is talc, and talc will absorb moisture....therefore if you get a paint chip, the filler can absorb moisture, which will then create RUST UNDER the filler) (**which is why every time I seem a guy driving around for weeks with a big patch of bare filler on their daily driver I just have to shake my head:)
AND, having attended MANY Paint Clinics put on by the manufacturers local Reps over those years, I also learned early on to not use the full strength metal preps (which are an acid) under etching epoxy (such as Ditzler/PPG's DP40, DP90, etc, but this was of course before the lead free "LF" versions were released)

I can kind of grasp the logic of filler over epoxy, for the barrier effect mentioned above, but my concerns are
1) Chemical Adhesion between an epoxy and a polyester?? (Until someone explains the chemistry behind this inter-racial phenomenon to me, I personally will only trust MECHANICAL adhesion!)
2) Cure time: Epoxy primers (and most 2K products) have a "window" of time where they can be topcoated without needing to be scuffed/sanded for adhesion. (this time varies from mfgr to mfgr)
However, for the application of filler, I believe they should be allowed to FULLY cure, then sanded for mechanical adhesion.
My reasoning is that with all products containing solvents, as the solvents evaporate, they "offgas" and application of filler to epoxy that is still curing may lead to solvents being trapped, or the potential for shrinkage after time as the offgassing takes place much slower after anything is added over top of the epoxy. (we could spend a couple hours just on this topic if we got into it:)

.....and yes, it seems every shop comes up with a method that works for them, but when one shop's approach is 180 degrees from the last, that tells me that their methods are based more on what they tried & got away with, or what was easiest, than any great amount of science:)
Bottom line is, even after being away from it for as long as I have, after first consulting with some paint reps, unless I receive some earth shattering revelations from the reps, my approach on my next project will be to do all the metal work, prep all the panels, give everything a bath in epoxy, then after sufficient cure time, scuff the epoxy where ever filler is required & carry on with body work from there..........

And as far as primer surfacers go, that is a whole separate topic, but we will leave that for another day/thread:):)

James

[LM14]

Quote.....Bottom line is, even after being away from it for as long as I have, after first consulting with some paint reps, unless I receive some earth shattering revelations from the reps, my approach on my next project will be to do all the metal work, prep all the panels, give everything a bath in epoxy, then after sufficient cure time, scuff the epoxy where ever filler is required & carry on with body work from there..........


That is where I am at on this too, James. I don't trust the chemical adhesion period but I know mechanical adhesion will work.

What are opinions on "kitty hair" being the first applied filler over welded-in patch panel seams or new panels on the weld seams. Since kitty hair is not going to absorb moisture like common fillers will, they are telling me to use it first in case there are pin holes in the seam allowing moisture in from the back side. They say kitty hair will seal the area better regardless of primer type used.

Isn't body work fun?
SPark

[grump]

"Kitty Hair" is great on the topside for waterproofing but it's going lose the battle if you have a pinhole or if rust gets started on the backside. Remember, the rust you see on vehicles usually starts on the back side from salt, limestone particles (fine stone), and water that gets trapped or just doesn't get washed off. That said I still like to use, in my case Duraglass, just try to make sure you get all the air bubbles out. That kind of filler always seemed to be hard to get all the air out of it when it's not really fresh, although that could be different now, I haven't used any in a few years.

[jamesdfo]

Steve/Grump: I have used Kitty Hair, but don't care for it.....I find it REALLY hard to spread smoothly, resulting in small voids (air pockets), which pretty much negates why you are using it. Kitty hair is long strands of fiberglass, pretty much like wetted out random strand matting. Might be OK for fixing a FG header panel, tail light extension, snowmobile hood, etc, but not for a "seal coat". I've had much better results with the chopped FG products, and there are many brands, Duraglass, Marglass, etc. Any of Fiberglass Evercoats products are generally of decent quality.
For a seal coat, I have also used some of the aluminum fillers, All Metal, Aluma Fill, etc (again, there are many)
The only thing I don't like about both of the above mentioned products is their lack of flexibility, generally this isn't an issue, but.....

I go to great lengths to get rid of pinholes in welds. On my bro's Chevy II, which is tubbed, when I did the wheelwell stretch (and RAISE), because the factory inner wheelhouse was removed for replacement by wheel tubs, we could take a trouble light and hold it up to the backside & check for light on the front side (helps to turn off shop lights:)
Generally, if you have anything on the length of your weld that looks sketchy, (from either front or back side) poke it with something sharp, if nothing happens, it's likely sound, if you penetrate, you know your work is not done:)

[jamesdfo]

Grump: because it is polyester based, if your can is getting "thick", you can add a very small amount of polyester resin (same stuff you use when laying up FG matting), this will make it "creamier"....but remember, the higher the resin %, the more brittle the product becomes......

"Kitty Hair" is great on the topside for waterproofing but it's going lose the battle if you have a pinhole or if rust gets started on the backside. Remember, the rust you see on vehicles usually starts on the back side from salt, limestone particles (fine stone), and water that gets trapped or just doesn't get washed off. That said I still like to use, in my case Duraglass, just try to make sure you get all the air bubbles out. That kind of filler always seemed to be hard to get all the air out of it when it's not really fresh, although that could be different now, I haven't used any in a few years.

[LM14]

I've used long strand and short strand product for filling/bonding glass to glass. Usually bond with strips of glass cloth or mat and do my rough fill with kitty hair type products.






I was just recently told to use it as a backer to protect from pin holes. I told him I wouldn't have any pin holes so I wasn't worried about it but 2 different friends have now insisted it's a great use for it.

I totally agree with Grump's assessment of kitty hair use. I was asking because I wondered how it could protect if rust started on the backside. Thanks for the confirmation.

SPark

[Arrowhead]

From SPI's epoxy tech sheet:

Body Fillers:
On any restoration it’s always best to apply the body filler over the epoxy rather than applying filler over bare metal for best adhesion and corrosion protection. After applying two coats of epoxy, wait overnight before applying the body filler. The epoxy does not need to be sanded before applying the body filler (for up to 7 days). If time allows, it’s always best to apply filler over the epoxy after it has set for 24-48 hours. If you choose to do the filler work over bare metal, the epoxy can be sprayed over the sanded body filler.

complete sheet is on page 8

http://media.wix.com/ugd/8ced3e_08f93c6 ... 324437.pdf