Working with EPS/Bead foam, and paper mache or paperclay.

[nathancarter]

Couple of questions from a novice prop maker. I'm pretty handy with tools and paint, but so far most of my props are cobbled together from found objects, not fabricated from scratch.

1) I have a very large amount of white bead/EPS foam that I want to incorporate into some props - the first of which is a huge ice chest that I scavenged from my day job, that I plan to turn into a Borderlands-style loot chest. Any tips on working with this foam? A couple thin layers of newspaper paper mache, sand it flat, then gesso, sand some more, then add details/paint? Will I have trouble with the paper mache sticking to the foam, and should do a thin layer of gesso directly onto the foam first?

2) When people refer to paper clay, do you usually mean the pre-packed "Creative Paperclay" product, or do you mean a homemade modeling substance made from pulped paper/TP mixed with a hardener and clay? If the latter, got any reliable recipes? I've seen a handful of different recipes on the net.


I just picked up some gesso, Apoxie Sculpt, and some sculpting tools, and might get started on some things this weekend. The chest and a helmet (expanding foam, insulation foam, or maybe white foam) will likely be my first projects. I need to pick up a hot-wire cutter too, I think.

[verdatum]

It sounds like you're on the right track

1) Using a heavier paper for your bottom layer gives you a more durable result. It just needs to be porous; like paper grocery bags or heavy construction paper.

White foam doesn't sand or rasp very well, so any adjustments should be made using hot tools or very sharp blades.

So long as you form a shell all the way around the piece, you don't need to worry about delamination (the paper mache pulling away from the foam). Keep in mind, if you do this to the lid, you will need to remove material to account for the thickness of the paper, or the lid won't close properly anymore. If you can't form a complete shell, then you can improve adhesion by lightly scuffing the surface with 220 grit sandpaper, and brushing a layer of white glue (aka PVA glue) onto the foam and applying the paper mache while the glue is still wet. This step is really just extra insurance though, it isn't usually critical.

If you do the process well, and you use decent brushes, you shouldn't need to sand after applying the gesso.

2) I suspect most people are referring to the Creative Paperclay, but only because they don't know that homebrew recipes work just fine. Being able to tweek the recipe for your needs can be really useful, particularly when surfacing or fixing flaws. Coating the entire surface with a slurry made by watering the recipe both helps to fill in low spots, and gives you a surface that sands more easily than the layer of paper strips. Mixing in a bit more glue gives you a paste that can be used to repair flaws and securely fill cracks.

[nathancarter]

Thanks.

I've already thought about the thickness difference in the lid. It's gonna be a challenge anyway since I want it to hinge in the back (as in the reference material which I haven't posted yet), instead of lift vertically off. I also want to finish and trim the inside so it's not just exposed foam. I don't expect it to thermally function as an ice chest any more, but it'll work for general storage and as a nice photographic prop.

[Penlowe]

If you opt to go the home recipe method, you can save a lot of money because the paper can be salvaged from recycling bins. Many home improvement & hardware stores sell PVA glue in gallon containers, also way cheaper than buying school sized bottles in mass quantities. (for a project this size, chances are you will need something close to a gallon of glue). I found using a blender to create the fine slurry coat is wonderful, but don't burn out the motor doing so.

If you like doing paper mache, I recommend getting a separate blender just for it, because nobody wants newspaper in the bottom of their pina colada