Body is a 1987 Corvette.

I've painted my car twice, and I'm still having a few (about down to 4 now) blisters.

Painted the car in Aug 2007, baked the CRAP out of it before we sealed it, after we sealed it, then a light bake on the finish coat.

Sat in the garage all winter, then came out in May and sat in the sun. By July some blisters in the paint popped up.

I've had the paint MFG test the samples chemically, and with their little photo camera. They are NOT solvent pops. It's the sealer/paint pulling AWAY from the body. The back side of the chip (if you cut the blister with a razor) is a little powdery, like it pulled some of the SMC off with it.

In many spots, the car was sanded to the factory SMC. Many many spots got a skim coat of body filler (said for use with SMC on the label). We use Sherwin Williams 2k sealer/primer, and their BC/CC.

I've painted a LOT of steel cars, and a LOT of fiberglass boats. Never an SMC car. (well, now mine twice). I don't know where the blistering is coming from. The only thing I can think of is maybe over time in the sun a few of the repair areas are releasing some type of gas but I would have thought the bake before we sealed it would have fully cured the body filler. And it's NOT happening on the LARGE repair areas, just on some minor areas. I'm pretty sure the areas it's happening on all got a very small skim coat..

Most of them are on the hood (many repairs) and passenger door (few repairs). I'm thinking about just junking the hood and door, but I still have one blister on the body right behind the door where I slipped with the DA and made a small imprint in the body. I did a light body fill. This one, if not all, needs proper fix so I can reshoot that side of the car again.

Any thoughts??

 

Dont trust polyester body fillers that say use with SMC. Use all epoxy products including primer.

 

That is an interesting descrepency from what I was told a few years back. I was told epoxy is just for fiberglass not SMC. Then sherwin williams (both the rep, and then the tech support) told me not to use an epoxy primer on the SMC car..

Now I'm confused..

I've always used either epoxy or straight up resin and cloth to fix boats.

-- Joe

 

Please post a pic of the blister that is on the quarter panel. Can you be more specific about the brand and type of filler you used, and give me some details on the paint products you used including reducers and hardeners?
What is your surface prep and cleaning procedure prior to applying filler?

 

I'll snap some pix tonight, and grab the label off the can of filler. was some green stuff that the supplier recommended.

The paint, reducer, hardner, sealer, etc was all provided by sherwin williams as part of their dimensions system. (image attached).

We (err I mostly) sanded the whole body down - car had been painted like 5 times). Most spots had to be sanded to the white SMC. I had to fix a few problems, mostly in the hood and some cracks on the rear quarters. Some marks in the door from god knows what, etc. Filled, sanded.

Then we wiped the car down twice with 2 gallons of prep clean (I think I used dupont brand). Then I towed the car to a friends booth.

He wiped the hole thing down, and sanded a few spots with some guide coat, them made a small repair on the hood using some polyester filler.

I was concerned about flash time so he agreed to paint it.

About 2 months later the car blistered EVERYWHERE.

We sanded it all back down. He used a different brand polyester filler than I had used (i'll have to find out) and re skim coated every spot. Then baked the crap out of it for a few hours, then shot it with 2k primer/sealer, then paint.

I can't tell with 100000% certainty the spots that have re-blistered are areas that I originally filled, or are re-blisters of areas he fixed. My guess is the filler is the culprit, but I don't understand the blister.

In the sun/heat the blisters turns into big bubbles. When the sun goes down they retract and is almost not noticeable.

-- Joe

 

Sorry 'bout all the questions, can you elaborate on the flash time statement?
You may have more than one problem. Awaiting your answer, I'm leaning towards 2 problems. One, an adhesion problem due to surface contaminants and/or solvents used to clean the car, along with the possibility of not enough flash time from filler through the paint process (too much product too quickly for conditions). I looked at the weather history site and August '07 was a very hot and humid month except for only about 5 days. Not ideal paint conditions and certain precautions need to be observed. The fact that the spots enlarge when hot indicates some activity (air or chemical) still present below the surface.

 

I can shoot single stage paint, boats, etc really good. I'm not soo good with BC/CC. I understand it's simple for a lot of you guys, but I'm not an auto body man. I wanted to leave it to the guy whos been painting for 30 years..

I can tell you a few things:

1) The first time it was painted (feb 07) It was not humid. Second time may have been.
2) It was painted both times in the spray booth.
3) When we cut open the blisters the first time, the SW rep checked it with this little camera thing, and we did a sniff test on all the blisters to see if it was solvant evaporating and poping. Nothing was wet, it was all dry. However, it did appear to be..Dusty almost. Like it was pulling some of the SMC off with it..

My buddy who owns the paint shop doesn't want to ever see my car again. I have not cut or refinished the existing blisters because I want to do a little research.

Another friend of mine mentioned that, as the car was sanded over a 1 month period in my shop (when I had the shop), and work was performec in adjacent bays he wonders if airborne silicone/grease made it's way into the very porous SMC. I did a 'prep clean' wipe down before sanding, and when we were complete but for the 29 days or so in between that I sanded I didn't prep clean the body every time. I guess a possibility exists that something airborne could have fell on the body, and I could have sanded it in..??

I've never had this problem sanding/painting steel body cars or painting boats. I went out of my way to arrange a booth and better painter to do this for me, and it came out worse (both times) than anything I've ever done myself.

I gotta snap some pix of the blisters. I'll try tomorrow. It gets dark too soon.

-- Joe