Most first armor builds come down to two materials. EVA foam is cheap, light and forgiving. Worbla is a thermoplastic that turns soft and sticky under a heat gun and hardens again as it cools. Plenty of builds use both: foam for the shape, Worbla for the shell. Here’s what each one is, what you need to work it, and how to stay safe while you do, using the manufacturers’ own instructions and safety data sheets wherever we could.
EVA foam, the cheap and light starting point
EVA foam comes in a range of thicknesses, colors, densities and chemical makeups, as Kamui Cosplay explains in her guide to creating costumes with EVA foam. The cheapest source is interlocking floor mats, about 10 mm thick, with one textured side that takes extra work to smooth. High-density sheets in 10, 5 and 2 mm are smooth on both sides and more durable. Softer black foams are cheaper and lighter, and easier to heat-shape.
Test a scrap before you commit. Kamui notes that some foams shrink when heated and some melt. On foam that shrinks, cut lines open up and carved details pop. On foam that melts, the cuts can close up again the moment you heat them.
The tool list is short. Kamui’s basics are a box cutter or craft knife, a rotary tool for sanding edges (a flex shaft helps with detail), a heat gun and contact cement. Dremel’s own foam helmet tutorial adds a cutting mat, heat-resistant gloves, a marker and a wooden coffee stirrer for spreading glue.
To shape foam, Dremel suggests running the heat gun on its lowest setting over the inside of the piece for about 30 seconds, then bending it by hand; the foam curves toward the heated side. To glue, both guides spread a thin layer of contact cement on both edges and let it dry before pressing them together. Dremel allows 10 to 20 minutes. Kamui warns that the bond can be strong enough to tear the foam if you try to pull it apart, so line the pieces up before they touch.
Worbla, a plastic you shape with heat
Worbla is the brand name for a line of thermoplastics sold as sheets and pellets. The sheets are about 1 mm thick. According to Worbla’s sheet instructions, Finest Art, Black Art, Mesh Art and FlameRed Art activate at 90°C (195°F), using a heat gun or an oven. Warm, the sheet is flexible, stretchy and sticky. Cool, it’s hard plastic again. Worbla says the material has no shelf life, can be reheated endlessly, and that Finest Art scraps can be reheated and blended back into usable material, so mistakes aren’t wasted. Its work time is 30 to 90 seconds before it needs more heat.
The varieties behave differently. Worbla describes Finest Art as the original, brown with an orange-peel texture. Black Art is smoother and takes fine detail best, but it’s the least adhesive and tears if stretched. Mesh Art is the stickiest, and FlameRed Art has a flame retardant built in and stretches further. Detail work leans toward Black Art; easy joins lean toward Finest or Mesh.
On armor, Worbla rarely works alone. Its instructions describe the “fold” and “sandwich” methods: cut the shape from flat foam, cover it in Worbla to give it body and stop it warping, then join the pieces. Heated pieces stick to each other if you heat both surfaces. Once they’re cool, Worbla recommends glues meant for plastics, such as contact cement or epoxy.
Worbla’s tool list: a heat-safe workspace, a basic heat gun, parchment paper or a silicone sheet, scissors, water, pens or markers and work gloves. Heated Worbla sticks to wax paper, foil and most plastics, but not to parchment or silicone. Water cools your fingers and stops the plastic sticking to them. Worbla suggests a heat gun with the on/off switch at the grip, and starting on the lowest setting with a powerful one.
Two storage warnings from Worbla’s FAQ. Finest Art begins to soften at about 65°C (150°F), and a car in the sun can get hotter than that inside, so never leave sheets or finished pieces in a car. And keep sheets loosely rolled at room temperature, because very cold sheets can be brittle. Sheets run from a 14 × 9 inch sample to a 39 × 59 inch jumbo, and Worbla says one large sheet is always cheaper than two smaller ones.
Sealing and painting
Raw foam drinks paint and Worbla’s texture shows through, so both need priming. Dremel’s helmet guide heat-seals the finished foam with a heat gun before priming, then builds up several coats of primer with a foam brush, letting each dry. Kamui lists three common foam primers: Plasti Dip, a spray-on rubber that takes about three coats and which she describes as toxic and flammable; latex, cheaper and brushable; and Flexbond, which dries flexible so paint is less likely to crack.
Flexbond works on Worbla too. Worbla says it can smooth Finest Art to a paintable finish in as few as three coats and Black Art in two, dries clear, stays flexible, and is water-soluble, so drips and runs are easy to fix. Worbla’s own surface takes almost any paint, though many people prime first because of the texture. One finish it shows: Worbla primed with gesso, painted with metallic acrylic, rubbed with Rub ‘n Buff and sealed with clear satin spray.
Safety, from the data sheets
In a first build, the material that needs the most respect is usually the glue. The safety data sheet for DAP Weldwood Original Contact Cement, a common solvent-based contact cement, classifies it as a highly flammable liquid and vapor. It warns that vapors can flow along surfaces to a distant ignition source and flash back, and says to keep it away from heat, hot surfaces, sparks and open flames. It says to use it only outdoors or in a well-ventilated area, opening windows and doors for cross-ventilation. Listed hazards include respiratory irritation, drowsiness and dizziness. The sheet recommends solvent-resistant gloves, says an organic vapor respirator may be necessary where vapor levels exceed exposure limits, and advises wearing a properly fitted NIOSH-approved respirator if you get watering eyes, a headache or dizziness.
Put plainly, a heat gun and wet contact cement don’t belong in the same moment. Let glued seams dry and the fumes clear before you heat-shape or heat-seal. Formulas differ between products, so read the data sheet for the exact can you buy.
Worbla’s safety data sheet for Finest Art is mild by comparison. It says the product isn’t classified as hazardous and that breathing, hand and eye protection aren’t required. It also says the material can decompose slowly with localized heating above 150°C and warns of toxic pyrolysis products, so don’t scorch it. Worbla’s FAQ adds that a hot knife needs proper ventilation, and that gloves are necessary for TranspArt and Crystal Art, which are worked hotter than boiling water.
With foam, most of the risk comes from tools and finishes. Dremel’s tutorial says to put on goggles, a dust mask, ear protection and gloves before sanding, and goggles, gloves and a respirator for airbrushing, in a well-ventilated room. Kamui says to spray Plasti Dip outdoors or with good ventilation. And give the heat gun a place to rest where the nozzle can’t touch anything, as Worbla advises.
Where to buy
Worbla names Cosplaysupplies.com as its North American online partner and lists chains such as Blick Art Materials and Tap Plastics among its retailers, with a full store list on its site. Foam is easier to find: floor mats are the budget option Kamui mentions, and dedicated cosplay suppliers sell high-density sheets. Our prop and supply store directory collects reviews of shops that sell both. If you’d rather commission the armor than build it, browse our maker directory, and when it’s finished, find somewhere to wear it in our convention listings.