Thinking about the paint job

[tradmedic]

Hi folks, I have a couple questions about painting the water resistant foam board. I understand that a light sanding is generally a good idea before painting. My question is am i trying to sand off the top wax completely, or just scuffing for paint adhesion?

Also, I bought some of this acrylic-polyurethane primer to test out with the airbrush. When working with regular DTFB, would this take the place of minwax polyurethane?

 

[FDS]

You want the surface of the paper to be completely dull, without sanding through it. I use 4-600 grit auto paint or a medium Scotchbrite pad to key the FT board.
Then light coats with a good flash off time between layers, you want the layer below touch dry before building more paint.

 

[kdobson83]

Just lightly sand it. Your not trying to remove anything, just trying to scuff the surface so that the paint has something to hold onto. And no need to add any waterproofing to the water resistant foam. The light scuffing you do to apply paint won't hurt it's waterproofing. If you sand hard or too much it will tho.
Basically like mentioned above, lightly sand with some fine sand paper, 400+ grit, or some scotch bright, until the paper has a whiteish/foggy tent to it. Then apply paint in light coats.

 

[Keno]

I questioned the Krylon People on this subject about the coating that is use to make WRFB and the coating used is a product intended to stay wet so to speak or waxy, dry to touch, but in fact never truly never dry. Krylon stated that they have no paint or primer that can absolutely adhere to the coating. This is why you have to scoff up its surface for paint to stick, and you must let your coatings dry completely. There are printing products that do work on this surface but I don't think they would be suitable for our use. By the way I have used the poly coating and it seems to help but it adds weight.

 

[FDS]

You always have to sand a non absorbent surface before painting, likewise very few systems are wet on wet.
It’s true that the FT board is a difficult surface for paint.