Things You'll Need
UV-reactive markers or spray paint
Stencils or painter's tape
Fabric marker or chalk pencil
Reflective ribbon or fabric
Some clothing is woven or knitted with ultraviolet-reactive or metallic, reflective threads, so it naturally -- and permanently -- illuminates beneath a blacklight or when you shine a light on it in the dark. If you'd like to retrofit your everyday clothing to light up in the dark, an option exists for every skill level: From seamstress-level embroidery to free-handing with UV-reactive markers or stenciling with glow-in-the-dark paint.
Blacklights and Pigments
Lay the clothing out flat and draw patterns on it with UV-reactive markers; the patterns you've drawn in will glow under a blacklight. This is the perfect technique for drawing intricate patterns, coloring in an ominous "radioactive" symbol, or free-handing characters such as tiny, glow-in-the-dark fairies or ghosts.
Spray-paint the entire garment with a UV-reactive spray paint, or use stencils and painter's tape to confine the glow-in-the-dark paint to certain portions of the clothing. For example, use your painter's tape to block off vertical stripes on an old black suit. Then paint the stripes with white UV-reactive spray-paint to create a glow-in-the-dark Beetlejuice costume that really pops under a blacklight.
Mix glow-in-the-dark powder into water or paint; check the product label before mixing, because some powders will not mix with water or water-based mediums. You can also purchase pre-mixed paints with glow powder in them. Paint the powder mixture onto your clothing where you want it to glow, or use a spray bottle to apply it to large areas. This glow-in-the-dark effect doesn't require a blacklight, but it does need to be exposed to light so it can "charge"; once charged, it'll glow in the dark. The painted or sprayed areas will be visible as more subdued colors during the daylight.
Draw the pattern you'd like to trace onto the clothing with a fabric marker or, to be safest, a chalk pencil. Thread a tapestry needle with reflective yarn and stitch along the pattern lines, depending on the desired effect.
Apply reflective tape to the parts of your clothing you want to glow in the dark when illuminated -- for example, the cuffs of your sleeves and pants.
Stitch reflective ribbon into place over the areas you want to glow in the dark or, for costuming, cut your design pieces from panels of reflective fabric and applique onto your clothing.
You can also purchase metallic or UV-reactive thread and use it to embroider patterns onto your clothing, whether by hand or with a machine. If you're going metallic, make sure the thread actually contains metal filaments, instead of just being metallic colored; it's the filaments that will reflect a glow when light hits them.
Stay clear of the paint or markers until they're dry; otherwise, they'll stain your skin: You'll glow in the dark too until the ink or paint washes off.