shrinkage problem???

[jk2paintworx]

I painted a dash piece that was modified to hold a tv screen in a custom audio video installation. The a/v guy made some fairly major mods and fill work. I painted the part for him about a week after he made the mods. Now 6 monthes later the guy calls him becauuse of some major shrinkage. I looked at the part and you can see all of the modification lines in the part. When I painted it it was perfect. I am not sure what products or procedures he used, but I would like to know the correct ones so it does not happen again. Also what should I do to fix this piece? I would hope that all the shrinkage is finished buy this time. Can I sand back down and re base/clear? Should I seal?

[Mike K]

Bunch of "unknowns" here.
What all did you use for starters.
Most likely, he used the old Bondo as most homebrew jobs are. First mistake.
That stuff should be outlawed cause it's just CRAP!!
It will suck up solvent,primer,paint like a sponge. Then, it starts cracking or falling out in chunks.
Any filler work should be sealed with epoxy IMO first then 2k primer.
Epoxy will seal it up and your shrinkage is nill.
Spot your filler with a couple coats of 2K and let it DRY,then finish priming if epoxy isn't in the plan.
You bomb the primer on over the filler and it's soaked in solvent and you "think" it's dry,paint it then after some time it "finally" dries out and you see the results.
As for fixing what you have,That depends on how bad the shrinkage is, Very light, sand and repaint it if you think paint will fill it up but most likely sand and reprime,dry overnight,block if needed and then paint.

[skidlid]

lots of things like already said can cause shrinkage: poor body filler, improper plastic sanding with final grit too coarse, poor primer, rushed flash time on primer, primer not allowed to sit long enough before sanding. Sand last coat of plastic with something finer like 180 or 220. Prime with good primer and make sure to allow flash times. Sand out primer after cure allow extra time so that it will reduce shrinkage, even 2k will shrink if rushed. If the video guy used any panel bond adhesive in his work this product will ghost line at different temps. Panel bond is not recomended for bonds where seams are flush or overlapped on flat panels. You can try to hide the seams with a good coat of fiberglass filler over top of seam.

[DocCyber]

all materials shirink...controling that shrinkage and managing it at the right time is why what we do is a profession.

everyone who piped in here has gone thru shrinkage school......hehehehe

make sure whoever works on your pieces before you, has been to shrinkage school also.....

I just did a job where the upholstr'er put 2 screws thru the roof of a paint job i did..........it took 5 dayz to shrink out 2 screw holes so they wouldnt ghost.......i dug out the paint and removed all loose chips around the hole....filled with polyester putty.shrank that did it again..then applied uro fill primer 3 times with 6 hour dry times in between.....featherd that out and cleared with 3000 spot clear.....then came back dusted on some color to fade in the spot then cleared........all for 2 holes that where sheetrock screw sized.......yea........all that to get rid of ghosting

[KrazyKusch21]

all materials shirink...controling that shrinkage and managing it at the right time is why what we do is a profession.

everyone who piped in here has gone thru shrinkage school......hehehehe

make sure whoever works on your pieces before you, has been to shrinkage school also.....

I just did a job where the upholstr'er put 2 screws thru the roof of a paint job i did..........it took 5 dayz to shrink out 2 screw holes so they wouldnt ghost.......i dug out the paint and removed all loose chips around the hole....filled with polyester putty.shrank that did it again..then applied uro fill primer 3 times with 6 hour dry times in between.....featherd that out and cleared with 3000 spot clear.....then came back dusted on some color to fade in the spot then cleared........all for 2 holes that where sheetrock screw sized.......yea........all that to get rid of ghosting


ummm are u saying u used the filler 2 fill the 2 screw holes?????? god i hope not..or did u do some metal work

[DocCyber]

i filled the screw holes with bondo........nothing wrong with that.......i couldnt do metal work because the 10 grand paint job was 2 weeks old.....shrinking your bondo so its stable and then using a hardened primer was the best solution.........ive been thru shrink school......my fix will work fine.

been there done that......ive fixed a lot of paint.

[Mike K]

Doc, What exactly do you mean by "shrinking" the bondo?
That some secret 70's procedure from the old daze? Hehehe.

[DocCyber]

yea its called patience and time....:)

if you read how i shrunk out the bondo then shrunk out the primer........all i did was let the bondo shrink on its own untill it was cured then shaped it.same with the primer......you cant bondo today and paint tomorrow.......i wish i could have welded the holes shut but that option wasnt available so i did what was next on the list of fixes.........5 days to shrink out less then a pencil erasor sized spec of bondo and catalized primer......i did add a drop of fiberglass resin to the bondo just to make it more stable....and that was so it wouldnt have any absorption properties

[Slamin Sam]

Like Doc said, Patience & time...........& more time. When you use bondo you cannot be in a hurry, it is not made for production work.
Years ago some so-called Bodymen made bondo into a 4 letter word.
I have done just what Doc has stated, I have even put as much as 5 gallons of bondo on 1990 GT Mustang quarter panel, not because I wanted to but because the customer didn't want to change the panel. That was 1995 & last year he came back so I could work on the front (ran over by a deer). The quarter still looked good. Oh, by the way the car is BLACK, so that says it all.
There are not to many true bodymen in my area, mostly parts changers. So I get a lot of work to fix others mess ups, even have acouple of bodyshops that call me to do work that their guys can't do.

Sam

[Mike K]

So, Your talking about actual BONDO then. Not the poly fillers used today right?
I've actually never used the real bondo I always used the poly stuff cause of the crap bondo is.I've seen plenty of it on repairs and the shrinking and cracking were good enough sign to stay away from it.
Guess it does have a good use for something after all.

Or am I still missing something here?

[Slamin Sam]

It's all basically the same. It has improved over the years though. I tend to use Evercoats line of body fillers, prefer to use the Rage Gold. I also use the Keystone brand of filler, keylite gold & their poly putty, you can mix them to gather & it spreads like butter. But even the best of the stuff will shrink & crack if not applied properly.

Sam

[DocCyber]

all fillers are the same.the difference is how finly ground the filler material is. The new filler is ground fine so it settles better then then ol stuff...plus they make it creamier so it helps settle better removing pinholes.

dont over harden bondo...that causes heat which causes craters and pinholes.

but yea rage gold is top shelf.

you have to top all fillers with a polyester primer for the best possable job.

If your not topping your bondo with polyester primer like mortons eliminator your not taking the full tripp.....polyester primer..then bondo..then polyester primer is the best 1-2-3 punch.....not saying you have to...just saying it is the top..high end....and the best solution to bondo....you sandwhich it in between polyester.

Mortons eliminator is a sprayable polyester with extra resins........the stuff is un-be-leavable for shaping and holding the shape of a great molding job

[Mike K]

Thanks Doc. I use Featherfill G2 now and it seems to do a good job but I'll check into the Mortons to see if it's avil. local.

[DocCyber]

I would get on line and order it....do a google search, its available........its tougher then featherfill.......this stuff was kept secret in my shop for over 20 years......it always gave me an edge.

[Mike K]

I checked yesterday and I can get it local but would probbly get it cheaper online.
My supplier said if I want one that is as good or better, use the Standox.
He said that it was about the best going,but of course it's not cheap either.
Thanks, Mike.