Paint Bubble

[dragstk]

Im working on a 64 Dodge 330. Laid on the last coats of paint today, put it in the dehydrator and these 2 bubbles were there when I took it out.

The roof has putty in that area (quarter size low spot), but it never showed any problems with primer or paint. I used Tamiya putty, primer and paint. It has 2 coats of TS-13 black, 3 coats of TS-85 Mica red and 3 coats of TS-95 Metallic Red.

It always went in the dehydrator after every color. There never was any indication of paint problems.

I poked at the bubbles and they were hollow, and went all the way to the putty

Ive never seen anything like this. Anybody have any idea of what happened?

Thanks

[bobthehobbyguy]

I suspect that solvent in the putty was trapped under the primer and paint and the heat created the bubbles. How long did you wait before putting the primer on the body after applying and sanding the putty.

How long did you have the body dehydrator after each coat of paint.?

 

Edited December 19, 2023 by bobthehobbyguy

[64SS350]

I agree with the solvents being trapped under the primer. Could be the thickest area of repair that didn't fully cure.

I adopted the practice using thin CA to seal my putty, but I'm using body glazing. It soaks in and fills sand marks also. In addition, I use it when sanding the body, to fill sand marks and destress the plastic. Molded raised areas have a "memory", and will reappear.

Anyway, hope this helps.

[Mark]

Do you always put acrylic lacquer jobs in the dehydrator?  I don't see the need to do that, as Tamiya spray dries faster and harder than enamels.

[bobss396]

3 hours ago, Mark said:

Do you always put acrylic lacquer jobs in the dehydrator?  I don't see the need to do that, as Tamiya spray dries faster and harder than enamels.

Before my dehydrator took a dump on me... everything went into it. Primer, paint, glazing putty. I can't say anything for enamels, I haven;t used any in about 25 years.

[Mike 1017]

This has never let me down. I always wait a day for it to dry then sand it.

[Skip]

1 hour ago, Mike 1017 said:

This has never let me down. I always wait a day for it to dry then sand it.

Or an hour or two in the dehydrator and its ready to sand.

[bobthehobbyguy]

You said the depression was the size of a quarter. How deep was it?

If it was fairly deep then it might of required several applications. If the is the case a 2 part putty is the better choice as it doesn't require the evaporation of solvents and it can be applied in heavier coats.

[dragstk]

Thanks for the replies.

@Bob- The depression wasnt that deep, more of a low spot. I didnt see it in the plastic but saw it when I block sanded the primer. I would guess is was maybe a 1/64" deep

Since the paint bubbled all the way to the primer, I did think that maybe it was the putty.

It went in the dehydrator for at least 3 hours after every coat of paint, @95 degrees. And there was a full day between every coat of paint

@Karl-Thanks Karl. I will try the CA trick

@Mark-I know Tamiya paint drys pretty quick. I put all paint in there regardless of type. I just get a little "nervous" handling freshly painted parts, especially the last color coats

@Mike- Ive never tried spot putty and since Ive never had an issue with Tamiya putty, never thought to try it. But Ive seen other builders also like it, so maybe its time I give it a try

@Skip-Your right Skip, it was ready to sand after a couple of hours...sand the bubbles off..?

 

If it was the putty, why did it wait until 8 coats of paint were applied? I certainly would understand if it showed up in the first coats

Thanks to all of you for taking the time to reply and make suggestions

[bobthehobbyguy]

That is a mystery however the one thing that stands out to me which implies to me that it was something in the putty as the bubbles went down to the putty and that means it was under the primer. 

[Mark]

Did it go in the dehydrator after the putty was applied?  If it went in after any two steps were performed together, there might lay the problem.

[dragstk]

@Bob- I agree is seems like the putty is the issue. Its just weird that it chose to show up after so much time and under so much paint

@Mark-No, I didnt put the body in the dehydrator when doing the putty. Tamiya putty dries so fast I didnt feel the need to

[bobthehobbyguy]

How long did you prime after you applied and sanded the putty?

[bobss396]

20 hours ago, Skip said:

Or an hour or two in the dehydrator and its ready to sand.

Less is more with this stuff. A cycle in the dehydrator will ensure it shrinks completely, no surprises later on.

Speaking of dehydrators, I picked one up at Ollies yesterday. $39 but has a temperature control on it. I have to find some plastic sheet to make a surround for it. My last one was made from 10" chimney flashing, a bit too high.

[Mark]

One-part putty (especially the red Bondo product) is nothing more than extremely UNthinned lacquer primer.  It shouldn't be applied in thick layers, and even when applied properly (thin layer) a visit to the dehydrator is in order before moving to the next phase of bodywork.

[dragstk]

@Bob T- About a day. I tried to never rush this. Every different color of paint and primer were always at least a day apart, with trips to the dehydrator for every color.

@Bob S- Thats why I put things in the dehydrator, but I still got surprised. ?

@Mark- Thanks Mark, Ill keep that in mind

[bobthehobbyguy]

I would say if you are going to use a solvent based putty then I would recommend it goes in the dehydrator before priming. I don't think that this is an issue with just the Tamiya putty it's an issue with any solvent based putty. As far as the bonds spot putty I would recommend using that for areas that need a little putty and not used for the type of depression. Hope this helps.

[dragstk]

Thanks Bob.

Just to tie this up. While I dont really know what happened, but I did fix it.

I cleaned out the spots the best I could. Then a couple times a day, I dabbed a spot of primer into each circle, until it was just proud of the surrounding paint. Sanded that down with some wet/dry 200 grit. Then resprayed. And this time, no issue.

Thank you to all that replied

Jeff