Glow in the dark paint is a common nickname for phosphorescent paint, which is ultimately paint infused with phosphors. The phosphors produce luminescence when exposed to white light, opposed to fluorescent paint, which glows only when exposed to ultraviolet rays (black light). Many paint stores offer glow in the dark paint, but you can make your own version with a paint medium and some phosphors. These phosphors are commercially sold as glow in the dark powders and come in many different colours and strengths.
Choose your glow in the dark powder. The phosphors will glow for only so long at a time, so compare and contrast the glow duration, glow brightness and glow colour among different powders. The strength of the powder is measured in microns. Note that the larger phosphors will glow strongest, but they will also produce a rough painted surface. You should also consider the daytime versus nighttime glow colour and whether the powder is compatible with a water-based paint medium.
Choose a paint medium. A paint medium is a base substance used to apply the phosphors to your surface. A clear solvent or acrylic paint will work best. You can use white paint, but your glow will not be as strong. Make sure it is a clear paint medium and it is compatible with your glow in the dark powder. If your glow in the dark powder isn't compatible with a water-based medium, don't try to use it with a water-based medium. It won't work.
Pour the paint medium into a plastic bucket and add the glow in the dark powder. Your mixture should at least be 20% powder. The glow in the dark powder is measured in grams and paint is measured in ounces or litres, so the measurements aren't correlated. You will have to convert the powder measurements to liquid measurements before mixing.
A simple mixing guide:
250ml of paint medium to 125g glow in the dark powder
500ml of paint to 250g powder
1 litre of paint to 500g powder
2 litre of paint to 1kg powder.
You can add more phosphors until you reach a glow level that suits you.
Use a wooden mixer to mix the powder with your paint medium. Do not use a metal mixer or bucket; this can negatively react with the phosphors. Do not mix different phosphor colours with each other because their glows will cancel each other out.
Use your glow in the dark paint on a white surface for best results. The darker the surface, the worse the results. Mix your paint medium every 10 to 15 minutes because the phosphors will sink to the bottom of the medium. The phosphors will be at the bottom of your bucket within an hour.