Minwax Polyurethane treatment of foam board tests
I took a scrap wing and treated half with the
Minwax (OIL BASED) polyurethane and left the other half untreated. I then take both sides under the microscope so we can get a closer look at what both sides look like.
I then test both premium and cheap spray paint, brush on acrylic (as a demonstration of what not to do) and test the water repentant aspects of both treated and untreated sides. I don't have an airbrush but chad already did an amazing job documenting that aspect of painting. When you try this do it on a scrap to get a feel for it.
Hopefully this will answer any outstanding questions around the Dollar Store Foam Core + Polyurethane topic.
You can see more of the details in the following stills.
You can see the Poly changes the color cast of the white
This is the treated side under the microscope
This is the boundary, treated on the left untreated on the right under the microscope
What not to do or How NOT to paint your foam core.
Water applications
The water beads on the treated side while the untreated soaks the water up
Notice that even though this is NOT how to paint you can see that the treated side takes the paint just fine.
The paint right from the tube soaks into the untreated surface and the maskting tape pulls the whole surface up.
Here you can see the surface sheen of the spray paints on the treated, background section, and the untreated, foreground.
The rest of these are closeups of the boundary with the treated on the left and untreated on the right.