Foam Props and Armor – An Overview

Once upon a time, I attempted to make fiberglass armor and claws for a Zhang He costume. With time running out before Otakon, I revisited an idea that I had never thought would work for me – craft foam propmaking. I’d come across Amethyst Angel’s famous craft foam and styrene tutorial, but that technique and I just did not get along. First off, I didn’t like having to bend the piece properly in a single step. More importantly, hot glue hates me. It dribbles, burninates my fingers, and doesn’t seem to find a middle ground between having near zero holding power and warping the plastic laminate layer.

With inspiration from Yui’s amazing skills and lots of my own experiments, I came up with a foam crafting method that works for me.

Zhang He - In Flowers


Materials

Firm, thick foam. My favorite type thus far is Volara, a closed-cell insulation material similar to a cross between craft foam and a camping mat. Its surface is very durable. I was unable to gouge it with my fingernails, and I could temporarily tape it all I wanted to without ruining it. Volara doesn’t give off nasty plastic fumes, and it is incredibly forgiving to heat shape. It won’t tend to warp or dent or collapse in thickness. I could undo any bend I made, and I didn’t leave finger dents in the process. I’ve used a commonly available formulation (type A – judging from the density, probably 2A), which costs $3.50 – $4 or so per 60″ wide foot. If you order it in quantity, even with shipping charges, it’s much cheaper than craft foam. You might be able to find it locally and avoid the shipping cost. I’ve happily ordered from foambymail.com

My main problem with 2A Volara is that it can’t be carved. It’s possible to make neat simple cuts with a craft knife, but it’s too sproingy for anything more complicated than that. If you want carvable material, you’ll have to go for expensive super-dense closed cell foam. WingedSephiroth recommends the LD50CN high density polyethylene from esdproducts.biz. trabus has told me that Volara 6A, which I don’t know where to purchase, is very close to a piece of foam he bought from a Japanese gundam maker a while back. I haven’t played with any of this material yet.

Craft foam can work well, especially if you want a smooth painted surface without the subtle texture of Volara. For a previous version of my Zhang He claws, I used the extra thick craft foam sold at JoAnn Fabrics. This foam is dense and stiff with a smooth, somewhat waterproof surface, and it is about as forgiving as Volara to heat shape. Downsides – it comes in smallish sheets, and its surface isn’t as durable. You can temporarily tape it to some extent, but you have to be careful.

Scissors. Be sure that they are sharp and sturdy enough to leave a nice edge on your foam.

A heat source. I would suggest an electric stove or even an electric hot plate. It provides a uniform source of heat that you can wave the pieces over just long enough to soften them without burning them.

Trim and other 3-D decorating materials. You can use thin craft foam, media for drawing raised designs (Gem-Tac glue, puffy fabric paint), cording, vinyl aquarium tubing, and anything else that can be glued to your base foam. The round edging on my Zhang He armor is cotton duck upholstery piping.

Gesso. If you’re painting on craft foam or other porous materials, you may need to seal them first. Volara is waterproof and can be directly painted if you’d rather work with the texture than put a boatload of time and elbow grease into trying to hide it. Any cheap gesso will do – no need for the fancy artists’ varieties.

You may wish to try other water-based sealants, but be sure to experiment. I didn’t care for Zinsser Bulls-Eye 1-2-3. It won’t level as well as gesso does, it can’t be sanded, and it wound up peeling right off the foam.

Be aware that gesso can pull out heat curves in a piece, which is a problem noted with Volara. I mainly recommend it for structural craft foam and decorations that won’t hold a paint job without it.

Glue. I generally use Mod Podge to attach foam decorations to the base pieces and E-6000 for structural gluing, such as adhering plates to one another. If you get along with hot glue, that works too. I prefer slower-drying glue because it gives me a chance to scoot things around until they’re positioned just the way I want them.

Paint. Cheap craft acrylics aren’t bad, but the artist-grade paints are worth the extra money – especially metallics. Water-based spray paint should work as well.

The Process

1) Pattern your prop or armor.

Without a CAD program that can flatten 3D models into patterns for me, I use the ever so scientific technique of experimenting with stiff construction paper and masking tape. I guess at the shape of a piece as well as I can. (For example, I made the initial draft of a chest plate by tracing the arm and neck holes of a tank top.) Then I cut out the shape and try it on. If it’s not quite right, I alter it until it works.

2) Cut out and shape the pieces.

Put the electric stove on medium-high heat, wave a piece back and forth over the burner for a count of 3 to 5, and then curl it in the direction in which it needs to curve. Some curves may take a bit of work to figure out. If an edge needs to curve steeply, try rolling it up after you heat it. Hourglass pinches in the middle of plates are tricky but very well possible. To achieve these, pinch the sides of the plate together, wave it over the stove, and then keep it pinched until it cools. If you bend something too far, just reheat it again. If it doesn’t relax on its own, you can manipulate it back to its original shape. Always err on the side of using too little heat. You can always reheat and redo a not bent enough piece. If you burn it, it might be ruined.

If your piece has darts, you will obviously need to glue them together. Since the strongest adhesive I’ll use indoors is E-6000, which does not instantly bond, I clamp my darts with tape. First, tape the dart together tightly. Working in sections on the back side of the piece, squeeze beads of E-6000 onto a craft pick and shove them into the dart. Ensure that the front edges of the dart are still lined up the way they ought to be, and let the piece sit until the glue cures. Extra glue can be carefully pinched off when dry. (Don’t yank at it too hard and take a divot out of the foam!)

This procedure is best done with Volara. Craft foam can get dented during the process of manhandling darts that require effort to assemble tightly. Its surface may also be damaged from being taped.

3) Seal the pieces (if necessary) and apply trim.

The order of operations depends on what sort of decoration you’re adding. If you’re gluing on large pieces of thin craft foam or some other porous material, do this before applying sealant. If you’re working with puffy paint or Gem-Tac, you’ll probably want to do this afterward so you don’t have to worry about gesso filling in small corners and details of the design. If you’ll be gessoing and sanding a surface that will get any sort of trim that is annoying to sand around, get all of that done first. You can carefully apply sealant to finicky porous decorations later on.

4) Paint.

I’m a fan of mottled finishes, which are fun and easy to produce by dabbing different colors of acrylic paint all over the piece. They also work well with the texture of Volara. To make decorations “pop”, I shade around them with darker paint.

5) Assemble the piece.

I glued the gauntlet plates together with E-6000. Any strong glue of your choice should be fine. Layered plates can also be sewn with a heavy needle and thread, which is a better option if they need to have some mobility. If you go this route, do so before applying the trim so you can cover up the stitching.

Various Thoughts on Surface Finishing

If you have plastic that is flexible enough for the task at hand, you can glue that over the foam instead of sealing it.

Stretch vinyl cemented over foam can produce jaw-dropping work, as seen on the sites of a well-known mech builder and another Japanese armormaker. This method is particularly notable because it can produce a smooth, seamless, and shiny surface on a piece with compound curves.

Gesso adds durability to the surface of craft foam. The pieces won’t hold up in combat or survive a nuclear blast, but they will get through a crowded convention with little in the way of lumps or bumps.