Paint shrinkage on plastic

[Acuratechva]

Hey hey, so i am having hard time figuring out what is going on.

During prep of plastic headlights, for clear coating, the plastic adhesion promoter wrinkles/shrinks. On light first coat its fine then when i go for full coverage is when i get wrinkles.

If clear the light off the bat with no adhesion promoter, paint shrinks/wrinkles right toff the bat, all the same. However if i apply adhesion promoter then paint and then sand smooth the wrinkles...then clear over, finish is fine.

Pretty much in any situation, if wrinkles in the clear are sanded, and clear dries the final finish comes out fine. It does not re-wrinkle

For the hell of it i sprayed a plain clear plastic nut tray, went heavy just to see what happens......NOTHING, no wrinkles.


Any pros know what is going on? All i can see is that both fresh paint and adhesion promoter contain reducer... must be a chemical reaction between raw plastic and reducer?

 

[K13]

Every adhesion promoter I have ever used and the one the company I work for sells says to spray one light coat. Sounds like you are putting way too much on which is a common occurrence with adhesion promoters.

 

[Acuratechva]

Well i guess you have not seen all of them.

 

[spudley]

You got me at "re-wrinkle"...

 

[like2wheel]

What is the final grit are you sanding to before the clear?
2k clear?
I've never used adhesion promoter on headlights







.

 

[Acuratechva]

What is the final grit are you sanding to before the clear?
2k clear?
I've never used adhesion promoter on headlights
.

Yup, eastwoods european clear that has given great results for ever. Usually 6-800

 

[like2wheel]

Yup, eastwoods european clear that has given great results for ever. Usually 6-800

No help from me then, never had a problem with that process. Maybe the lens is not polycarbonate?
I did actually sand out & polish a set today, as prep for protection film. Want to see how that works out. Might be a solution for situations like yours.

 

[SGKent]

use this one. Best on the market. When you coat the final time make sure you don't go over it because it dries almost instantly. You get one shot at painting the clear because it dries so fast. I use something that I can pour the clear in that is wide enough to accept the folded cloth they give you to coat with. That way you don't run out or get light 3/4 of the way across.

I think that the chemical they use to help remove the old crazed poly is Bleche-White. It smells the same. And the clear looks and smells like Spar-Varnish but I can't be sure. I will say that the headlights I have done looked factory new when finished.

 

[ard]

how long are you allowing between coats? Some stuff Ive seen (admittedly not headlights) is 'OK in one hour, then wait more than 24hrs'.... I hit it at 12, and wrinkles.... (so I dont hit it at 12 any more...)

HTH