Glow in the dark piping gel sounds like something worth trying for a cake, but it's tricky to find pre-made products to make it work. The secret ingredient is the quinine in tonic water, which naturally fluoresces under a black light. Colored piping gel is available at cake supply stores. Add tonic water to the piping gel at home to make it glow, or make your own custom-colored glow in the dark piping gel from scratch for a better glow in the dark effect.
Pre-made Piping Gel Glow
Measure 2 cups of the piping gel and place it into a saucepan.
Add 2 tbsp. of tonic water to the piping gel and mix together in the saucepan.
Check the piping gel consistency with a spoon. If the mixture sticks to the back of a spoon, fill the plastic squeeze bottle with the piping gel and use.
Add 1 tbsp. of powdered unflavored gelatin to the mixture (if the mixture is too runny for piping). Warm the gel mixture in the saucepan on a stove top on low heat until the piping gel thickens to the proper consistency.
Empty 2 cups of cold tonic water into a saucepan, then sprinkle 2 tbsp. of unflavored gelatin to the water. Wait 5 minutes for the gelatin to dissolve.
Warm the mixture over low heat until the tonic water and gelatin mixture is clear.
Add 1 1/2 cups of light corn syrup to the mixture and heat through, but do not boil.
Remove the piping gel mixture from the pan and spoon into a bowl or storage container. Cool the piping gel, then refrigerate until ready to use.
Take the clear piping gel out of the refrigerator. Dip a toothpick into the gel food coloring just enough to coat the toothpick. Dip the gel coated toothpick into the piping gel and mix in the color. Add more gel food coloring using this method until you get the color you want.