Radioactive Symbol Halloween Costume Iron-On Patch

The trefoil radiation symbol, 4.5 inches across and circular. It reads three ways depending on where it lands: costume prop, lab humour, or straight graphic design. All three are valid reasons to buy it, and the size is generous enough that it works as the only patch on a garment.

What it pairs with

It sits naturally alongside the glow skeleton and the Occupy Mars circle, which is the same 4.5-inch round format — two matching circles on opposite sleeves is a clean, deliberate look that a single patch cannot achieve. For a hazmat or post-apocalyptic costume it is usually the anchor piece, with everything else arranged around it.

Fabrics it bonds to

Cotton, cotton blends, denim and cotton canvas. Cotton boiler suits and coveralls — the obvious costume base — press cleanly.

Fabrics to sew instead

Thin polyester costume fabric is the trap: it glazes under a hot iron and the shine does not come out. Sew it. Same for nylon, coated or waterproof shells, leather, faux leather, vinyl, and anything with a print underneath.

Applying it

Flatten the area, position the patch, cover with a thin cotton cloth, and press with firm dry heat, working from the centre outward so the round edge does not lift. Let it cool completely. Stitch the border if the costume is being stored and reused, or if it is going on a garment you actually wear.

Care

Inside out, cold, gentle, low tumble or hang. No bleach, no fabric softener. Iron from the reverse side only.

Questions we get

Does it glow? No. This one is standard embroidery — see the glow-in-the-dark collection for designs that do.

How big is it? 4.5 inches across, about the width of a drinks coaster.

Will it hold on coveralls? On cotton, yes. Stitch it if they get washed hot.