When you're looking to take your homemade costume to the next level, adding lights is a great touch, especially for science fiction and fantasy outfits. LED lights are well-suited for incorporation into costume design because they produce a large amount of light without the need for much power and without producing uncomfortable amounts of heat. Successfully lighting a costume piece using LED lights requires obtaining the best lights, positioning them well, and designing a costume that lends itself to being illuminated.
Purchase the smallest, brightest, battery-operated LED lights you can find. Look for lights with the smallest unlit body and battery casing portions so that they won't add more bulk to your costume than they do light. Look for lights whose switches don't require constant squeezing in order to remain turned on. If possible, get lights with bulb and dome shapes rather than flat lenses, as this will project light in more directions. Purchase more lights than you think you will need.
Use long-life batteries, if possible. You will need to keep the lights on during both construction and the span of time when you're wearing the costume, so get batteries designed for long life, such as camera batteries.
Secure the lights in the "on" position. If lights have sliding switches, tape them down. If they are pressure switches, turn them on, then tape a hard, flat object (such as a coin) over the switch so that it won't accidentally be turned off while you're wearing it. Skip this step if your costume design will allow you to reach the lights to switch them on and off.
Every area of your costume that you want to have lit will, ideally, be made of rigid material to prevent anything flopping over the light and blocking it. Lit areas should also be thick and dark enough to keep light from showing through except where you want it to; materials like styrofoam, sheet metal, plastic, and paper board are all good options.
Cut holes in your rigid material to let light shine through. Plan the positions of holes according to the number of lights you have; make sure none of the holes is too far from a light that you want to be seen.
Create extra reflective surfaces inside your costume, if necessary, by lining areas with aluminium foil. This will not be seen, but it will disperse the light inside the hollow areas and ensure that all of the holes you want light shining through will be bright enough.
Angle the lights so that the bulb is pointed to shine out of the holes you've cut.
Attach the lights in position on the rigid material using a heavy-duty tape, such as duct tape or gaff tape.