Very Unique Bondo Problem! Paint Screwing it up?

Grayscale · 12-05-2004, 09:54 PM

Alright. I thought I had all my fabrication problems worked out, but I guess not. I bondo'd the dash you see in my avatar this summer, and then decided to do some work on my console, such as removing the ashtray and coinholders and putting in a touchpad and some buttons to control stuff. Anyways, I had a few problems at first with getting the bondo to dry hard. Turns out it was the bondo/hardener consistency. After getting that all worked out, I did all the shaping and made it look perfect. And the bondo was rock hard. I used the same exact paint stuff as last time, obviously to match.

First I gave it two coats of Bulldog Adehsion Promoter. I was having adhesion problems when I very first started with bondoing, and the guy at this paint store gave me it. It worked good. I just put a couple of coats on over the bondo, then was able to spray paint right on over that.

The spray Paint I used was Duplicolor Truck, Van, and SUV paint. It's not too bad, but I don't think it's made for plastics. Thats why I used the adhesion promoter. I put a coat of it on over the bulldog stuff.

I also must say this: Before painting on the bondo there were areas where it looked more "slick". They were like rings, and they were a darker red than the rest of the bondo. When I painted on the console piece, after it dried the paint also looked smoother where the rings where. You will see these rings in the pictures.

So after the paint had 20 minutes to dry, I naturally pushed my fingernail into it to see if it was pretty solid. My fingernail fell right in. And I could scrape the paint right off the bondo. For some very strange reason the paint actually made the bondo go soft, and allowed me to scrape it off really easy. I was angry and i ripped part of it off, because I was going to have to start over anyways and it would be easier to replace the wood and rebondo than to sand it all. Well when I got home to take pictures most of the places where I had sanded on were nice and hard again.

So two problems: 1) What are the rings where it looks smooth and is really shiny? and 2) why did the bondo go soft? was it from the paint or the adhesion promotor?!?!

Sorry for the extremely long post, but I think I had to explain all of this to get a good answer! I put up a bunch of pix also, just so you will get to see what all is going on with this.

Grayscale · 12-05-2004, 09:55 PM

Here you see the bondo thats all crumbled from where I ripped part of the piece off. This is when it got hard again. Before you could kind of peel the bondo right off the wood because it got soft.

Grayscale · 12-05-2004, 09:56 PM

Here is a surface shot where I just kind of scraped the paint and the bondo a bit to let you see how that looks

Grayscale · 12-05-2004, 09:58 PM

Here is the adhesion promotor I used, and the paint I used. They were stored out in my garage in the cold (40-50), but I warmed them up by the furnace where I was working.

I should note: I did my bondo work and my painting in a nice warm shop where it was about 65-70 degrees I'm sure

Grayscale · 12-05-2004, 09:59 PM

Another close up of the bondo crumpled

Grayscale · 12-05-2004, 10:01 PM

To give you a better idea of what i was working on:

Grayscale · 12-05-2004, 10:13 PM

Just one more of the surface with the "smooth spots" and the darker spots...

Altimat · 12-05-2004, 10:19 PM

Did you use primer?

Bondo is like a sponge. Primer looks the same way when its first applied over bondo. You need to repair that, use good commercial-grade body filler like evercoat, prime severla coats, sand, prime again, repeat until all the imperfections are filled. Let every primer application cure overnight at least. It should look perfect when you apply the last coat of primer. then sand with 600 and paint.
I suspect the bulldog isn't recommended over bondo. Its made to soften whats underneath it. I wouldn't use it.

team canada · 12-05-2004, 10:29 PM

Can't necessarily diagnose your exact problem, but here's my take on things:

First of all, straight Bondo was the wrong product to use for this application. It has very little structural strength on its own, and should never be applied more than 1/8" think, and it looks like you've got almost a half inch layer on there.

Second, the soft spots you saw could possibly have been from simply not mixing your bondo and hardener thoroughly enough. Might be from the adhesion promotor, might not be, but that would be my guess... (but next time don't use the bondo at all at that stage).

Finally, as far as your paint goes, not all types of coatings will work together, so it could simply be a compatibility issue.

Next time try this, use a fiberglass resin or bondo glass to cover the piece you're working with, then only regular bondo or a spot putty to fill in the low spots, minor imperfections, etc. Then when you're ready to paint, if you're going to be using that duplicolor paint again, stick with duplicolor primer. It's always best (but not imperative) to match your paint with your primer, plus the duplicolor primer will provide a nice base to spray over anyways.

Best of luck to ya

Grayscale · 12-05-2004, 10:31 PM

Ahhh...It's made to soften whats underneath it. Well that will definately cause that I guess

. Ok, well the filler I have is pretty good. It's not bondo brand and it's not evercoat, I can't remember what its called but most of the shops around here use it aparently. Ok, so can you recommend what type of primer to get? I am kind of scared of them because my very first bondo job I used a laquer-based primer and it completely screwed up everything. So this will take like 3 nights just to get to be able to actually paint on it? If it looks great, then it will be worth it I guess! I'm getting a respirator first thing before next project! I accidentally inhaled after spraying bulldog a couple of times. That stuff is super strong. I can still feel the sort of burning sensation in my throat/lungs. I wonder if it made them soft?!

Altimat · 12-05-2004, 10:37 PM

I use PlastiKote sandable primer in black. That way if you do ever chip it its still black at least. And you get a better idea of your final appearance while you work.

Grayscale · 12-05-2004, 10:37 PM

Quote: Originally Posted by team canada

and it looks like you've got almost a half inch layer on there.

About the thickest it gets on this piece is 1/4" I've done 1/2" on my dash just fine though. But yeah I'm getting some bondo glass if I need to do some thick bondoing next time! I bet its faster to sand, too!

Quote: Originally Posted by team canada

Second, the soft spots you saw could possibly have been from simply not mixing your bondo and hardener thoroughly enough. Might be from the adhesion promotor, might not be, but that would be my guess... (but next time don't use the bondo at all at that stage).

I think i mixed them pretty good, but you're right, maybe not good enough. But the spots...I could see them before I even put the adhesion promoter on. They were kind of shiny, but they were still hard, so that is kind of odd.

Quote: Originally Posted by team canada

Then when you're ready to paint, if you're going to be using that duplicolor paint again, stick with duplicolor primer. It's always best (but not imperative) to match your paint with your primer, plus the duplicolor primer will provide a nice base to spray over anyways.

Ehh, I used that primer last time from duplicolor. It was called "Sandable filler primer," and it came out an orangish red. It was really nice and easy to sand and all. But it was laquer based. And that screwed everything up badly! So any alternatives? Or was I just doing something wrong? Because when I was using that primer I hadn't tried any adhesion promoter underneath it.

Thanks for all the great info guys!

Grayscale · 12-05-2004, 10:38 PM

Quote: Originally Posted by Altimat

I use PlastiKote sandable primer in black. That way if you do ever chip it its still black at least. And you get a better idea of your final appearance while you work.

Alright! Can I get it at Walmart, or a place like Autozone? Or do you get it from a specialized paint place?

Altimat · 12-06-2004, 12:14 AM

I think I bought it at Autozone.

Grayscale · 12-07-2004, 06:17 PM

All they have is Duplicolor stuff at Autozone...but I found out my problem. And I know why my last few bondo projects have turned out fine. Bondo is porous and paint seeps in. I knew that, but never thought it would make the bondo soft. My problem was that the bulldog adhesion promoter was getting seeped in making it soft. The reason my stuff worked before was because I had already allowed a lacquer based primer seep in and then had sanded it off because it sucked. The laquer primer was still in the pores and it didnt soak stuff up after that. Aparently I need to seal the bondo and then put sandable primer over it and paint it. They have Duplicolor brand Sealing Primer. So i'm gonna get that. And then use Sandable Primer. They also have Sandable "filler" primer. Should I get that or just the sandable primer? After a few coats of that I'm gonna paint on it. I think i got all this figured out now. So just a FYI, BONDO SOAKS PAINT IN AND WILL GET TACKY AND NOT DRY.

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