how to make custom fluorescent light fixture for black lights
Black lights get much hotter than regular fluorescent bulbs. And like regular fluorescents, they need a grounded metal surface to be close to the full length of the bulb. Together, these mean the fixture housing should be in metal. So, unless you have the capabilities to make the fixture out of sheet metal, I would recommend that you buy a cheap, regular fluorescent fixture and swap out the a ballast and/or tombstones as needed to drive the black light tube you have purchased.
All fluorescent lights use a ballast to transform the voltage of the available electrical power to the required voltage for specific fluorescent tubes. The ends of the tubes are held in place and connected to the electrical current through the same device, it is called a tombstone. There is usually one tombstone on each end of each fluorescent tube. Buy the black light fluorescent tubes you want, buy a matching ballast, usually one ballast for each two fluorescent tubes, and buy the correct tombstones that will fit the end of the light tubes. There is always a wiring diagram on the ballast, showing how all the color coded wires properly connect to the power supply and the tombstones respectively. Use flame resistant materials to build the fixture. The ballast does not have to be in the fixture, but it does have to be mounted to materials that will not burn and will allow for cooling or venting, as it generates heat.
