I am not sure we are talking about the same product.
The SignFoam4 I am looking at comes in a variety of densities, up to 70 lb./cu.ft. That is DENSE foam! I am looking at the 20 and 30 lb./cu. ft. foams. I am not talking about styrofoam here.
The suppliers told me that they MUST be properly primed (two to three coats) and then painted, with NO part of the surface exposed, to prevent UV breakdown. There are resins and other coatings that can be applied to SignFoam4 that give it a ceramic appearance, and make the sign last.
Well, I stopped in at three suppliers and they inundated me with sample boxes and ringed chips of various materials and assorted color samples, etc. It looks like my material options are limited to the PVC boards like Sintra Board and the foams like SignFoam4, as well as the usual plexiglass and polycarbonate offerings.
I just thought there might be something else to work with, but the industry has been remarkably uninventive in coming up with a variety of new materials. There are lots of WOODS to work with, but the synthetic, man-made materials in anything thicker than poster board are sorely lacking.
I was hoping to find a source for rigid, clear or colored plastic sheets, rods or blocks that could be machined, cut, bent, formed and so forth. Think of Jello, but without the wiggles! Apparently, no one has had the vision to manufacture bulk synthetic materials that drift too far away from the traditional stuff.
You know how people make beautiful ice sculptures out of a large block of ice? Well, I was picturing large blocks of PLASTICS, clear, translucent or opaque, in 300 different colors, and dozens of different consistencies from rubbery (think of those pink erasers we had as kids) to rock solid but workable with cutting, sanding and shaping tools. We have blocks of ICE and blocks of MARBLE and GRANITE, and blocks of aluminum and glass and all sorts of other things, but not blocks of PLASTIC!
I guess I am expecting too much from humanity.