Paint problem

no I've havent seen that before but paint a small patch of the color of choice see if it covers it up

Sounds like maybe the Bondo is still outgassing? 

Eaglecash867

Sounds like maybe the Bondo is still outgassing? 

 

Either that, or an oil contamination can cause that effect.  Finger oil (especially in warm sweaty weather) can give that effect.  I often wash surface with alcohol just before painting, and either wear gloves, or hold model or part with something else so I don't need to touch surface while painting.

 

I've seen pin holes in hardened Bondo and similar products. I don't know what happened in your case. I'd probably just fill the pin holes with plastic putty and carry on as usual from there. Just about any plastic putty should work, even something from a hardware store.

Probably unrelated: Decades ago now I used a glazing putty called NitroStan to fill pin holes before final priming in 1/1 automotive refinishing.

What are you thinning the filler with?

 

Bill

Hi guys! Thanks for trying to help me with this problem. It's really bugging me becaue it's never happened before.

Nick - I was thinking of just spraying the finish color over them and hope for the best but if it doesn't work then it's back to square one down to the bare hull again.

Eagle - The Bondo was mixed up in a jar months ago. I just took a couple of drops of it out of the bottle, put it on the glass on the workbench and mixed in a drop of thinner. It was already pretty thin but I thought it would have to be thinner to fill those small pinholes.

Don - Washed it down with alcohol after filling and sanding, primered it and let it sit a couple of days. I wear the blue nitrile gloves when wiping down and switch to a clean pair for spraying.

Bill - I've been thinning the Bondo with lacquer thinner for years with no problems.

Hope I've answered your questions. I just remembered something I read a while ago about filling pinholes in resin with thin CA (I think).  The hull is not resin but would the process be the same? Am I right? Could this be a solution? If so, I'll give it a shot.

Jim 

Stay Safe.

 

 

fox

 

Hope I've answered your questions. I just remembered something I read a while ago about filling pinholes in resin with thin CA (I think).  The hull is not resin but would the process be the same? Am I right? Could this be a solution? If so, I'll give it a shot.

Jim 

Stay Safe.

I use CA as a filler almost exclusively.  Can't really speak to how it would work with pinholes in bondo though, if that's what you're asking.  If you are talking about filling those small depressions with CA to begin with, that's definitely a good method.  The beauty of using CA as a filler is that it stays put unless you deliberately try to remove it.  It doesn't let go just because the stuff next to it is disturbed like most other fillers tend to do.  I apply the CA to what I want to fill, whether it be a ejector pin mark, a pin-hole, a seam, etc...and then let it cure undisturbed, overnight.  No need to fill it with any other material, just the glue by itself works just fine.  After it cures, I scribble the whole area with a black sharpie, including a little bit of the adjacent area.  That acts as an indicator when I'm sanding to let me know that everything is level and there are no low spots, high spots, or pin holes.  Wet sand with progressively finer grits until all the black is gone.  Put primer on it, and you're done.  Very rarely do I have to do the sand-fill-sand-fill dance like we have to when using putty or bondo.  Its such a trouble-free, reliable process, it makes me wonder why I ever used the other stuff.  You can also apply it right over the primer if you find that you missed a spot, as long as you dab it on and don't disturb it until it cures.

Maybe it's just a thin or weak spot in the plastic and the solvents in the putty and paint ate through. Sometimes it happens with lacquers and such. Its just too hot. I'd try to fill the holes with something water based and maybe spray a barrier coat of something on and around those spots before going on with your regular paints. Super glue might be ok but it gets so hard sometimes it's difficult to level with the surrounding area. If you use Future or have some other acrylic paint that would serve as a barrier coat. Just a thought. And don't get me wrong, I use lacquer more than anything, so I'm not trying to discourage their use.

Not disparaging super glue either. :-) Eagle's reply wasn't there when I started typing.

Thanks for all the tips guys!

As the huill now has those spots sanded down to bare plastic, I'm going to try the thin CA. If it works, great. If not, I'll try the barrier coat. I don't think it's the Bondo because I've used it for years without this happening. Oh well, there's always a first time, right?

Jim 

Stay Safe.

fox

Thanks for all the tips guys!

As the huill now has those spots sanded down to bare plastic, I'm going to try the thin CA. If it works, great. If not, I'll try the barrier coat. I don't think it's the Bondo because I've used it for years without this happening. Oh well, there's always a first time, right?

Jim 

Stay Safe.

 

Are there holes in the bare plastic ? Should go fine if not. Well really it should go fine anyway.

Yep! The holes are in the plastic. They showed up after filling and sanding some indents then putting the primer on. Resanded the spots, filled with Bondo and primed. Holes came through the Bondo and primer again. 

Haven't done the CA yet as I'm working on a couple of planes for the museum. I want to get them done and off the bench.

Jim 

Stay Safe.

Put the CA on last night at around 1:30 (sorry, it's this morning). Sanded it down around 11:00AM and shot a little primer on it and it looks good. At 4:30 this afternoon, I put the color on and it looks great. The CA worked fine. 

 Thanks a lot guys for your help. 

Jim 

Stay Safe.

fox

Put the CA on last night at around 1:30 (sorry, it's this morning). Sanded it down around 11:00AM and shot a little primer on it and it looks good. At 4:30 this afternoon, I put the color on and it looks great. The CA worked fine. 

 Thanks a lot guys for your help. 

Jim 

Stay Safe.

 

 

That's awesome !

We used to do pin holes in both balsa and in foam on RC aircraft with CA. Sand off a little of the substance the kit was made of and drop some sanding dust in the hole followed by a drop of CA, instant filler lol. Never tried it with plastic but no doubt it would work. And the thing is it goes poof and it's cured.