What things do I need to consider before painting a star mural?
What Color ceiling/walls are to be painted?
The best color is white, followed by shades of white then light colors. The worst colors are dark colors, although tan and sandy colors appear to be rather bad too.
I'm not sure why certain colors are worse than others though. I'll take a stab and suspect that certain colors absorb rather than reflect the light emitted by the glow in the dark paint.
For example my master bedroom has a white ceiling and tan walls. The stars on the ceiling glow great but the stars on the wall will only glow if charged by a strong UV lamp. The tan walls are by no means dark though.
What light source is available to charge the star mural?
A ceiling fan with a light fitting works very well because it is usually centered in the room providing consistent coverage. Wall mounted lights and corner lamps will provide localized light and will take longer to charge the glow in the dark paint. Recessed lights will not charge the glow in the dark paint effectively due to the light having to reflect off surfaces back to the ceiling. The general rule of thumb is: Imagine yourself laying on the ceiling looking down. If you can see light bulbs then you'll get some charge. The more bulbs that can be seen and the more even they are distributed in the room the better.
What type of light source?
Well those 60W incandescent bulbs will charge the glow in the dark paint but it's going to take a while. A UV strip light will charge the room pretty much from anywhere but glow in the dark paint at the other end of the room will take longer to charge than paint nearer the bulb. Placing a UV strip in the middle of the ceiling is not usually an option. However, CFL bulbs actually emit UV light, they have a coating that is excited by UV light and emits light in the visible spectrum. So by swapping out your bulbs for CFL's not only will you reduce the energy used but they will charge the glow in the dark paint up very well.
I changed out the bulbs in my kids ceiling fans for 16W CFL's. Now when the main light is turned out the glow in the dark stars are clearly visible even with the night light on. With incandescent bulbs the stars were not visible until the nightlight went out.
What color GID paint?
OK this one is fairly obvious but it's still worth a mention. If you're looking for bright stars then use Super Green or Super Aqua glow in the dark paint. Anything with a lower brightness of the Super Aqua will not shine very bright or for as long. Red, Violet, Yellow, Deep Blue and White glow in the dark paints are all very nice but they need UV to work well. My violet paint will not even charge using incandescent light unless I leave it next to a lamp for an extended period of time. Even under UV it takes a few minutes to charge up the glow in the dark paint well.
What size stars?
The final variable I can think of. Super Green or Aqua you can get away with some rather small stars that shine really bright. As the brightness of the glow in the dark paint diminishes you can buff up the visibility by making larger stars or by grouping many stars together. I typically paint 1/4" to 1/2" stars for constellations and down to 1/8" for background stars. Now painting larger glow in the dark stars to overcome paint and background color has its limitations.
While most any glow in the dark star mural can work under UV light be aware of the lighting conditions and the color walls/ceiling that you'll be painting on. Most if not all of us work under UV and that can give the impression that the mural will work after the job is done. This might certainly not be the case. Knowing this ahead of time will enable you to inform your client that a UV lamp or other lighting might be required to enjoy the star mural.