Paint-like finish with epoxy?

Just for posterity, the problem with applying polyester filler over 2K urethane is that the urethane stays slightly soluble, that is, it can be attacked by solvent to a certain degree, especially when not fully cured. Polyester fillers contain styrene, which is a reactive monomer, but is also a solvent in its own right. Styrene can and will penetrate and loosen the urethane substrate before polymerization in a worst-case scenario. This can cause adhesion failure. I have witnessed such failures.

There are protocols that can be followed that minimize the chance of failure, should the poly-on-2K procedure need to be done. It should be considered a non-standard, special case, and not SOP.

The above may or may not represent the official position of SPI, and @Barry is usually too busy to clarify.
 
When I restored my Mustang in 2015 I had also used Platinum Plus over SPI 2k when my blocking still came up short. I must have done that because that’s what the label for the filler also indicated. I never had any problems with it. I also moved slow so it was likely never done over fresh 2k.
 
In hind sight, I would have just done the rough filler work over my fresh epoxy. I have a GT40 replica waiting for it's turn, So I'll be researching fiberglass work next.
I looked at my timeline via the pictures I have been taking:
4/16 Fenders, deck lid, louvers, bumpers, etc in fresh epoxy.
4/18 Filler worked these parts
5/9 Fresh epoxy on these parts
5/11 2K high build
6/10 Fresh epoxy on body
6/12 2K high build on body
6/24 to present: Filler work on seams-body
 
Overall, I’m pleased with how it turned out. I’m going to pains SPI black on the hood and roof fora little different look. I sprayed the car mid day, and tackled all the other parts in the evening. It seemed like the parts painted had a little bit nicer finish on them than the car did. Not sure if that had anything to do with the primer sitting in a sealed paint
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cup for a few hours.
 
Having fun with different colored primers. Somewhat matches my ‘17350R that has a black painted roof. I didn’t do the rail panel.
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crashtech said:
Just for posterity, the problem with applying polyester filler over 2K urethane is that the urethane stays slightly soluble, that is, it can be attacked by solvent to a certain degree, especially when not fully cured. Polyester fillers contain styrene, which is a reactive monomer, but is also a solvent in its own right. Styrene can and will penetrate and loosen the urethane substrate before polymerization in a worst-case scenario. This can cause adhesion failure. I have witnessed such failures.

There are protocols that can be followed that minimize the chance of failure, should the poly-on-2K procedure need to be done. It should be considered a non-standard, special case, and not SOP.

The above may or may not represent the official position of SPI, and @Barry is usually too busy to clarify.
Click to expand...

Barry has also told me only Dolphin or Icing glaze over 2k not regular filler.
 
I suspect that not all fillers are compatible with the 2K. Mine had sat for a while before I started filler work...and the Platinum Plus is labeled to use over 2K urethane primer. The car probably won't be painted for a year or more. If a problem comes up between now and then, it will be addressed. I'm not gonna overthink it or worry about it unless something comes up. Live and learn.
 
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