If you're in need of a fluorescent dye to make an ordinary item look neon, consider making your own using nothing more exotic than a basic highlighter pen. The project is a low-cost alternative to buying pre-made fluorescent dye from a craft shop, where similar items can sometimes be expensive. Plus, using a highlighter pen gives you different colors to choose from, such as yellow, green or hot pink.
Put on a pair of rubber gloves to protect your hands from being stained by the highlighter.
Break open a highlighter in the fluorescent color of your choice. If you have trouble breaking it by hand, use a pair of scissors to cut the pen in half.
Pull out the felt ink piece from the pen's tube. The felt has the fluorescent dye in it.
Fill a jar with 1 cup of tonic water. Submerge the highlighter felt in the jar and leave for about half an hour.
Use the mix to dye the item of your choice. For example, you can fill a bucket with 1 gallon of hot water, pour in the fluorescent dye and soak a fabric garment in the dye bath. Or, pour the fluorescent dye into a vase of flowers to give the blooms a bright color.