Things You'll Need
Liquid laundry detergent
Blacklight paint is available ready-made at Halloween and party stores, but you can make your own blacklight paint at home, which will allow you to use a wider variety of colors. Adding a blacklight reflective material to the paint will cause it to glow under a blacklight while the paint will have a normal appearance in normal lighting. Experiment with ingredients to perfect your recipe, and don't worry about using exact measurements. You can always add more paint if your mixture becomes too thin.
Pour a small amount of liquid laundry detergent into a bowl. Shine a blacklight on the laundry detergent while in a dark room to see if the detergent glows. Some detergents contain bluing agents used to make clothes brighter, and these agents react to a blacklight. If your detergent does not glow under a blacklight, try a different brand.
Pour 1 cup of water-based paint into a container. Water-based paints include latex, acrylic and most craft paints.
Add 1 tbsp. liquid laundry detergent to the water-based paint. Stir the detergent into the paint until the mixture is uniform in consistency.
Shine a blacklight onto the mixture. If the glow of the paint is too faint, add more detergent until you are happy with the results. Keep track of how much detergent you add so that you can mix a larger batch of blacklight paint, if necessary, using the same ratio of paint to detergent.
Make a temporary blacklight paint by applying full-strength liquid laundry detergent to a surface with a paintbrush. Remove the paint after your party or event by wiping it away with a wet rag.