"foam coat" is an acrylic plaster with fiber embedded in the mix. When used right is very easy to work with, cuts well after it dries, sands well and forms a very hard surface on foam. Foam coat takes a bit of practice to use right. Apply it too thick and it cracks. Too thin it is weak and useless. It's hard to apply an even thickness coat and difficult to tell exactly how thick it is and if thick, can take a long time to dry to a workable hardness. The fibers, glass I suspect, can be very irritating and be lodged in your skin by simply picking up your work piece.
Looking at your ceiling piece, foam coat might not be the best choice. Too much detail. That would get lost smearing it with foam coat. You could cut the foam blank a bit shy of where you want it to be, smear it with foam coat to build up a reasonable layer (1/10th" maybe), then cut it again to a finished size. That would leave a uniform layer of foam coat. It would take a lot of effort to build up enough of that gunk. The best way to apply it is by smearing it with your hand. That causes the fibers to align horizontally which keep them from sticking up and provide the needed reinforcement for strength and to prevent cracking. Be sure to use heavy gloves or spend a lot of time with a bright light and tweezers.
I suggest you try epoxy which I find is easier to work with and provides an entirely different result. I like the West Systems epoxies myself. Paint it on and in two or three coats, you have a hard surface that will withstand a lot of punishment.
One real caveat with foam is that it dents extremely easily. You can put a thumb mark in it by picking it up. Foam coat doesn't provide any protection until it is about 1/16" thick. Epoxy, on the other hand, will make it pretty much dent resistant after the second coat. While Epoxy might cost twice as much as foam coat, the results are better and epoxy can be used for many things, unlike foam coat, which is pretty much a one trick pony.
Good luck!
Last edited by coryatjohn; 02-18-2019 at 12:01 AM.
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