Finishing grit for poly primer before urethane high build

[DCx]

What is a good grit to finish my poly primer to before I move on to urethane high build? I am using Eastwood Contour Poly and its FRIGGIN AMAZING! spraying it on with a cheap ebay 2.5 tip gun at 37psi with 4% reduction (twice activator volume) acetone and it lays down pretty smooth. Still a slight orange peel but I spray a heavy guide coat and hit it with 80 grit and its easily reduced to a fine powder that doesn't load up my sand paper.

Here was my plan:

1. spray 3 wet coats of poly
2. guide coat
3. block with 80
4. guide coat
5. block with 180...
6. ???????

that's were I stopped. I scuffed up a small section of 180 with some 240 and man is it smooth! still have material to sand.

do I stop at 180? go to 240, then 320, then urethane, 320, 400 wet.

OR

do I stop at 180, red scotch brite it then move to urethane, 320, 400 wet.


Fresh Poly


Blocking with 80


blocking out 80 scratches with 180 and lightly sanding with 240 by hand with an interface pad


Fresh poly on the body of my dads 67 Fastback

[dhutton]

Any quality 2k urethane should fill 180 scratches. I use SPI Turbo primer. Not sure I would trust the job to Eastwood/Kirker 2k.

Also would not apply that poly on bare metal. Quality epoxy only on bare metal.

Don

[Tsaints1115]

I'm sure the material spec sheets would have exactly what the manufacturer recommends for proper adhesion. Paint's a big dollar investment. I wouldn't guess on it.

[dhutton]

I'm sure the material spec sheets would have exactly what the manufacturer recommends for proper adhesion. Paint's a big dollar investment. I wouldn't guess on it.

Keep in mind tech sheets are directed toward collision repair, not restoration work. Huge difference in goals etc….

Don

[Tsaints1115]

Keep in mind tech sheets are directed toward collision repair, not restoration work. Huge difference in goals etc….

Don

Proper paint adhesion is proper paint adhesion. And collision repair is a huge chunk of the market compared to anything else so the last thing they'd want is warranty claims on any paintwork.

[dhutton]

Proper paint adhesion is proper paint adhesion. And collision repair is a huge chunk of the market compared to anything else so the last thing they'd want is warranty claims on any paintwork.

Yessir! Sounds like you’ve painted a lot of cars and you know your stuff….

[Tsaints1115]

A baker's dozen or so.

[DCx]

Any quality 2k urethane should fill 180 scratches. I use SPI Turbo primer. Not sure I would trust the job to Eastwood/Kirker 2k.

Also would not apply that poly on bare metal. Quality epoxy only on bare metal.

Don

I unfortunately live in California and about the only SPI products I can get my hands on are Epoxy and waterborne wax and grease remover. I have SPI epoxy on hand. I didn't strip the car to bare metal because of how pristine the existing old paint was. I just hit the car up with some 80 grit and shot the poly over it. The trunk deck had one tiny ding in it I used some glaze on.

The 2k urethane high build I have on hand is Upol system 20. its 4:1 and was recommended to me by my local auto body supply.

so the task at hand... do I stop at 180 and shoot the 2k high build or sand the poly as far as I can go?

[dhutton]

It’s not in the tech sheet but it should easily fill 180 scratches imho. Hopefully the paint god will approve….

https://www.u-pol.com/files/31617/up2253v-TDS-EN

Don

[Tsaints1115]

It’s not in the tech sheet but it should easily fill 180 scratches imho. Hopefully the paint god will approve….

https://www.u-pol.com/files/31617/up2253v-TDS-EN

Don

[dhutton]

The last Paint God on here went to prison….

Don

[Tsaints1115]

Nothing wrong with consulting directly with the manufacturer. Even a rattle can of Rustoleum has the prep, spray, recoat, and drying specs on it.

[DCx]

I ended up taking the entire thing to 320. I was pretty amazed how easy it was to remove 180 scratches with 320. Only gripe is my spray on guide coat clogged the 320 pretty bad. All in all I am happy with it, feels glass smooth. Poly is pretty much transparent, I have a few metal spots showing but its getting coated in 2k urethane primer tomorrow. I will try to wet sand it with 400 some time in the future. I am still working on the rest of the car.



should I use rattle can etch on the metal? my Upol primer states its DTM.