SEM prep question ??

[Mopar Crazy]

I'm restoring my 68 Grille.
I read the section on grille resto, it doesn't really say if these products need to be applied before paint, some guys used them and some didn't.

The question I have is SEM has 38353 Plastic Prep and 38363 Sand Free for paint adhesion.

My grille is cleaned with spray nine, and scuffed. How important is it to use these products, and should I use one or both

Thanks 

[twodko]

Hey,

My grille resto paint was SEM as well. I cleaned the grille thoroughly then lightly sanded it with 220 wet/dry. I did not use any SEM primers because I didn't think it was necessary, your situation may be different. Then I sprayed all of the black with SEM semi-gloss, let it dry a couple days and sprayed the finish coat. Here is where the fun begins.........I masked off all the areas that were black then shot it with SEM Titanium Silver. Dried a couple days them shot the finish coat. Finally, I lightly scuffed the surfaces with very fine grit steel wool, air hosed it and wiped it down with a barely moist piece of tee shirt. I sprayed the entire assembly with two coats of SEM semi-gloss clear, light scuffing in between coats. LIGHT coats are key. Turned out tits!

[BananaDan]

Both, but there's a catch.  First off, SEM's plastic and leather prep isn't an adhesion promoter, it's a prep cleaner.

You have go be careful with which adhesion promoter you use because the wrong one can mess up your plastic because it has acetone in it which affects certain types of plastic.  I did my 70 lower dash panels with SEM products and their tech support told me to perform an acetone test.  Get some pure acetone (nail polish remover, but make sure it's 100% acetone), wet the tip of your finger with the acetone and touch it to a part of the plastic piece you're going to paint.  I used the back side of my lower dash pads since you don't see the back sides.  If your finger gets tacky and starts to stick to the plastic because of the acetone, then you have to use Sand Free (38363) as your adhesion promoter.  If it doesn't stick and the acetone doesn't affect the plastic then you use their plastic adhesion promoter (39863).

This is the order they told me to use to paint plastics:

1. Clean thoroughly with SEM Soap (39362) and a 3M grey scuff pad.
2. Dry completely with a lint-free rag like a micro fiber.
3. Clean with Plastic and Leather Prep (38353)
4. Dry again with a micro fiber.
5. Spay the adhesion promoter appropriate for the plastic based on the acetone test.
6. Paint with 2-3 light coats.  They told me to use their Color Coat line, these paints are designed for flexible surfaces like rigid or semi-rigid plastic.  For my black interior plastics I used Landau Black (15013).

http://semproducts.com/Catalog.asp?prod=190

Also, make sure you read the instructions on each product.  One difference to note is with the plastic adhesion promoter, you let it dry before you paint, but with Sand Free you put on a medium wet coat and paint right over it while still wet and it does its magic as it evaporates.  Also, don't be afraid to call SEM's tech support.  The number is on their website and they are great.

[Mopar Crazy]

BD: going to follow step by step instructions this weekend and finish it off...
Thanks for the help and detailed information.. 

That's why this site is so awesome...
Pete