How to Make Fluorescent Liquid

Dye an outdoor fountain to make it look electric blue under black light.
••• neon glow on water image by ELEN from

Have you ever seen bottles that glow under black light and wondered how they do it? Sure, you can do it the easy way with a highlighter soaked in water, but that is only good under a black light. Make a bottle that glows in the sunlight and have everyone begging to know how you did it. You can make hundreds of these to decorate your house, your room or even a classroom. Maybe you would like to make a water fountain glow, or even a pond.

For Small Amounts of Water

    Decide what you would like to make glow. The bigger the amount of water, the larger the amount of fluorescein powder you will need to react with it.

    Fill the bottle or container with water.

    Use the spoon to get a small amount of the fluorescein powder and stir it into the water. A pinch will dye an entire bathtub full of water. The exact amount will vary depending on the strength of color you desire and the amount of water you are mixing it with.

    Add a black light to enhance the effect. The mixture will fluoresce a yellow or lime color under regular light and sunlight; under a black light the color will glow a more vivid bright green.

For Large Bodies of Water

    Pour in the amount of water dye needed for your body of water. One gallon will dye up to 2200 gallons of water, one quart will dye up to 550 gallons of water and one pint will dye up to 275 gallons of water.

    Mix and agitate the water to combine the water with the dye. If you are dyeing a fountain or a pool, the pump will do this for you.

    Add a black light to enhance the effect.

    Things You'll Need

    • Water
    • Bottles or other containers
    • Fluorescein powder
    • Stick or spoon (not to be used by anyone again)
    • Water dye
    • Black light source


    • The more black light you have near the water, the brighter the color will be.


    • Water dye will stain skin. Do not use where people will be swimming.

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